32 files changed, 2185 insertions, 1535 deletions

diff --git a/crates/ra_assists/src/ast_transform.rs b/crates/ra_assists/src/ast_transform.rs
index 9ac65ab39..3079a02a2 100644
--- a/crates/ra_assists/src/ast_transform.rs
+++ b/crates/ra_assists/src/ast_transform.rs
@@ -1,7 +1,7 @@
 //! `AstTransformer`s are functions that replace nodes in an AST and can be easily combined.
 use rustc_hash::FxHashMap;
 
-use hir::{PathResolution, SemanticsScope};
+use hir::{HirDisplay, PathResolution, SemanticsScope};
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
     algo::SyntaxRewriter,
@@ -51,7 +51,27 @@ impl<'a> SubstituteTypeParams<'a> {
             .into_iter()
             // this is a trait impl, so we need to skip the first type parameter -- this is a bit hacky
             .skip(1)
-            .zip(substs.into_iter())
+            // The actual list of trait type parameters may be longer than the one
+            // used in the `impl` block due to trailing default type parametrs.
+            // For that case we extend the `substs` with an empty iterator so we
+            // can still hit those trailing values and check if they actually have
+            // a default type. If they do, go for that type from `hir` to `ast` so
+            // the resulting change can be applied correctly.
+            .zip(substs.into_iter().map(Some).chain(std::iter::repeat(None)))
+            .filter_map(|(k, v)| match v {
+                Some(v) => Some((k, v)),
+                None => {
+                    let default = k.default(source_scope.db)?;
+                    Some((
+                        k,
+                        ast::make::type_ref(
+                            &default
+                                .display_source_code(source_scope.db, source_scope.module()?.into())
+                                .ok()?,
+                        ),
+                    ))
+                }
+            })
             .collect();
         return SubstituteTypeParams {
             source_scope,
diff --git a/crates/ra_assists/src/handlers/add_missing_impl_members.rs b/crates/ra_assists/src/handlers/add_missing_impl_members.rs
index c1ce87914..22e1156d2 100644
--- a/crates/ra_assists/src/handlers/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/handlers/add_missing_impl_members.rs
@@ -618,4 +618,54 @@ impl Foo for S {
 }"#,
         )
     }
+
+    #[test]
+    fn test_generic_single_default_parameter() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Foo<T = Self> {
+    fn bar(&self, other: &T);
+}
+
+struct S;
+impl Foo for S { <|> }"#,
+            r#"
+trait Foo<T = Self> {
+    fn bar(&self, other: &T);
+}
+
+struct S;
+impl Foo for S {
+    <|>fn bar(&self, other: &Self) {
+        todo!()
+    }
+}"#,
+        )
+    }
+
+    #[test]
+    fn test_generic_default_parameter_is_second() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Foo<T1, T2 = Self> {
+    fn bar(&self, this: &T1, that: &T2);
+}
+
+struct S<T>;
+impl Foo<T> for S<T> { <|> }"#,
+            r#"
+trait Foo<T1, T2 = Self> {
+    fn bar(&self, this: &T1, that: &T2);
+}
+
+struct S<T>;
+impl Foo<T> for S<T> {
+    <|>fn bar(&self, this: &T, that: &Self) {
+        todo!()
+    }
+}"#,
+        )
+    }
 }
diff --git a/crates/ra_assists/src/handlers/change_visibility.rs b/crates/ra_assists/src/handlers/change_visibility.rs
index e631766ef..40cf4b422 100644
--- a/crates/ra_assists/src/handlers/change_visibility.rs
+++ b/crates/ra_assists/src/handlers/change_visibility.rs
@@ -5,11 +5,14 @@ use ra_syntax::{
         ATTR, COMMENT, CONST_DEF, ENUM_DEF, FN_DEF, MODULE, STRUCT_DEF, TRAIT_DEF, VISIBILITY,
         WHITESPACE,
     },
-    SyntaxNode, TextSize, T,
+    SyntaxNode, TextRange, TextSize, T,
 };
+
+use hir::{db::HirDatabase, HasSource, HasVisibility, PathResolution};
 use test_utils::tested_by;
 
 use crate::{AssistContext, AssistId, Assists};
+use ra_db::FileId;
 
 // Assist: change_visibility
 //
@@ -27,6 +30,8 @@ pub(crate) fn change_visibility(acc: &mut Assists, ctx: &AssistContext) -> Optio
         return change_vis(acc, vis);
     }
     add_vis(acc, ctx)
+        .or_else(|| add_vis_to_referenced_module_def(acc, ctx))
+        .or_else(|| add_vis_to_referenced_record_field(acc, ctx))
 }
 
 fn add_vis(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
@@ -72,6 +77,143 @@ fn add_vis(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     })
 }
 
+fn add_vis_to_referenced_module_def(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let path: ast::Path = ctx.find_node_at_offset()?;
+    let path_res = ctx.sema.resolve_path(&path)?;
+    let def = match path_res {
+        PathResolution::Def(def) => def,
+        _ => return None,
+    };
+
+    let current_module = ctx.sema.scope(&path.syntax()).module()?;
+    let target_module = def.module(ctx.db)?;
+
+    let vis = target_module.visibility_of(ctx.db, &def)?;
+    if vis.is_visible_from(ctx.db, current_module.into()) {
+        return None;
+    };
+
+    let (offset, target, target_file, target_name) = target_data_for_def(ctx.db, def)?;
+
+    let missing_visibility =
+        if current_module.krate() == target_module.krate() { "pub(crate)" } else { "pub" };
+
+    let assist_label = match target_name {
+        None => format!("Change visibility to {}", missing_visibility),
+        Some(name) => format!("Change visibility of {} to {}", name, missing_visibility),
+    };
+
+    acc.add(AssistId("change_visibility"), assist_label, target, |edit| {
+        edit.set_file(target_file);
+        edit.insert(offset, format!("{} ", missing_visibility));
+        edit.set_cursor(offset);
+    })
+}
+
+fn add_vis_to_referenced_record_field(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let record_field: ast::RecordField = ctx.find_node_at_offset()?;
+    let (record_field_def, _) = ctx.sema.resolve_record_field(&record_field)?;
+
+    let current_module = ctx.sema.scope(record_field.syntax()).module()?;
+    let visibility = record_field_def.visibility(ctx.db);
+    if visibility.is_visible_from(ctx.db, current_module.into()) {
+        return None;
+    }
+
+    let parent = record_field_def.parent_def(ctx.db);
+    let parent_name = parent.name(ctx.db);
+    let target_module = parent.module(ctx.db);
+
+    let in_file_source = record_field_def.source(ctx.db);
+    let (offset, target) = match in_file_source.value {
+        hir::FieldSource::Named(it) => {
+            let s = it.syntax();
+            (vis_offset(s), s.text_range())
+        }
+        hir::FieldSource::Pos(it) => {
+            let s = it.syntax();
+            (vis_offset(s), s.text_range())
+        }
+    };
+
+    let missing_visibility =
+        if current_module.krate() == target_module.krate() { "pub(crate)" } else { "pub" };
+    let target_file = in_file_source.file_id.original_file(ctx.db);
+
+    let target_name = record_field_def.name(ctx.db);
+    let assist_label =
+        format!("Change visibility of {}.{} to {}", parent_name, target_name, missing_visibility);
+
+    acc.add(AssistId("change_visibility"), assist_label, target, |edit| {
+        edit.set_file(target_file);
+        edit.insert(offset, format!("{} ", missing_visibility));
+        edit.set_cursor(offset)
+    })
+}
+
+fn target_data_for_def(
+    db: &dyn HirDatabase,
+    def: hir::ModuleDef,
+) -> Option<(TextSize, TextRange, FileId, Option<hir::Name>)> {
+    fn offset_target_and_file_id<S, Ast>(
+        db: &dyn HirDatabase,
+        x: S,
+    ) -> (TextSize, TextRange, FileId)
+    where
+        S: HasSource<Ast = Ast>,
+        Ast: AstNode,
+    {
+        let source = x.source(db);
+        let in_file_syntax = source.syntax();
+        let file_id = in_file_syntax.file_id;
+        let syntax = in_file_syntax.value;
+        (vis_offset(syntax), syntax.text_range(), file_id.original_file(db.upcast()))
+    }
+
+    let target_name;
+    let (offset, target, target_file) = match def {
+        hir::ModuleDef::Function(f) => {
+            target_name = Some(f.name(db));
+            offset_target_and_file_id(db, f)
+        }
+        hir::ModuleDef::Adt(adt) => {
+            target_name = Some(adt.name(db));
+            match adt {
+                hir::Adt::Struct(s) => offset_target_and_file_id(db, s),
+                hir::Adt::Union(u) => offset_target_and_file_id(db, u),
+                hir::Adt::Enum(e) => offset_target_and_file_id(db, e),
+            }
+        }
+        hir::ModuleDef::Const(c) => {
+            target_name = c.name(db);
+            offset_target_and_file_id(db, c)
+        }
+        hir::ModuleDef::Static(s) => {
+            target_name = s.name(db);
+            offset_target_and_file_id(db, s)
+        }
+        hir::ModuleDef::Trait(t) => {
+            target_name = Some(t.name(db));
+            offset_target_and_file_id(db, t)
+        }
+        hir::ModuleDef::TypeAlias(t) => {
+            target_name = Some(t.name(db));
+            offset_target_and_file_id(db, t)
+        }
+        hir::ModuleDef::Module(m) => {
+            target_name = m.name(db);
+            let in_file_source = m.declaration_source(db)?;
+            let file_id = in_file_source.file_id.original_file(db.upcast());
+            let syntax = in_file_source.value.syntax();
+            (vis_offset(syntax), syntax.text_range(), file_id)
+        }
+        // Enum variants can't be private, we can't modify builtin types
+        hir::ModuleDef::EnumVariant(_) | hir::ModuleDef::BuiltinType(_) => return None,
+    };
+
+    Some((offset, target, target_file, target_name))
+}
+
 fn vis_offset(node: &SyntaxNode) -> TextSize {
     node.children_with_tokens()
         .skip_while(|it| match it.kind() {
@@ -192,6 +334,378 @@ mod tests {
     }
 
     #[test]
+    fn change_visibility_of_fn_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { fn foo() {} }
+              fn main() { foo::foo<|>() } ",
+            r"mod foo { <|>pub(crate) fn foo() {} }
+              fn main() { foo::foo() } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub fn foo() {} }
+              fn main() { foo::foo<|>() } ",
+        )
+    }
+
+    #[test]
+    fn change_visibility_of_adt_in_submodule_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { struct Foo; }
+              fn main() { foo::Foo<|> } ",
+            r"mod foo { <|>pub(crate) struct Foo; }
+              fn main() { foo::Foo } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub struct Foo; }
+              fn main() { foo::Foo<|> } ",
+        );
+        check_assist(
+            change_visibility,
+            r"mod foo { enum Foo; }
+              fn main() { foo::Foo<|> } ",
+            r"mod foo { <|>pub(crate) enum Foo; }
+              fn main() { foo::Foo } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub enum Foo; }
+              fn main() { foo::Foo<|> } ",
+        );
+        check_assist(
+            change_visibility,
+            r"mod foo { union Foo; }
+              fn main() { foo::Foo<|> } ",
+            r"mod foo { <|>pub(crate) union Foo; }
+              fn main() { foo::Foo } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub union Foo; }
+              fn main() { foo::Foo<|> } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_adt_in_other_file_via_path() {
+        check_assist(
+            change_visibility,
+            r"
+              //- /main.rs
+              mod foo;
+              fn main() { foo::Foo<|> }
+
+              //- /foo.rs
+              struct Foo;
+              ",
+            r"<|>pub(crate) struct Foo;
+
+",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_struct_field_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { pub struct Foo { bar: (), } }
+              fn main() { foo::Foo { <|>bar: () }; } ",
+            r"mod foo { pub struct Foo { <|>pub(crate) bar: (), } }
+              fn main() { foo::Foo { bar: () }; } ",
+        );
+        check_assist(
+            change_visibility,
+            r"//- /lib.rs
+              mod foo;
+              fn main() { foo::Foo { <|>bar: () }; }
+              //- /foo.rs
+              pub struct Foo { bar: () }
+              ",
+            r"pub struct Foo { <|>pub(crate) bar: () }
+
+",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub struct Foo { pub bar: (), } }
+              fn main() { foo::Foo { <|>bar: () }; } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"//- /lib.rs
+              mod foo;
+              fn main() { foo::Foo { <|>bar: () }; }
+              //- /foo.rs
+              pub struct Foo { pub bar: () }
+              ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_enum_variant_field_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { pub enum Foo { Bar { bar: () } } }
+              fn main() { foo::Foo::Bar { <|>bar: () }; } ",
+            r"mod foo { pub enum Foo { Bar { <|>pub(crate) bar: () } } }
+              fn main() { foo::Foo::Bar { bar: () }; } ",
+        );
+        check_assist(
+            change_visibility,
+            r"//- /lib.rs
+              mod foo;
+              fn main() { foo::Foo::Bar { <|>bar: () }; }
+              //- /foo.rs
+              pub enum Foo { Bar { bar: () } }
+              ",
+            r"pub enum Foo { Bar { <|>pub(crate) bar: () } }
+
+",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub struct Foo { pub bar: (), } }
+              fn main() { foo::Foo { <|>bar: () }; } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"//- /lib.rs
+              mod foo;
+              fn main() { foo::Foo { <|>bar: () }; }
+              //- /foo.rs
+              pub struct Foo { pub bar: () }
+              ",
+        );
+    }
+
+    #[test]
+    #[ignore]
+    // FIXME reenable this test when `Semantics::resolve_record_field` works with union fields
+    fn change_visibility_of_union_field_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { pub union Foo { bar: (), } }
+              fn main() { foo::Foo { <|>bar: () }; } ",
+            r"mod foo { pub union Foo { <|>pub(crate) bar: (), } }
+              fn main() { foo::Foo { bar: () }; } ",
+        );
+        check_assist(
+            change_visibility,
+            r"//- /lib.rs
+              mod foo;
+              fn main() { foo::Foo { <|>bar: () }; }
+              //- /foo.rs
+              pub union Foo { bar: () }
+              ",
+            r"pub union Foo { <|>pub(crate) bar: () }
+
+",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub union Foo { pub bar: (), } }
+              fn main() { foo::Foo { <|>bar: () }; } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"//- /lib.rs
+              mod foo;
+              fn main() { foo::Foo { <|>bar: () }; }
+              //- /foo.rs
+              pub union Foo { pub bar: () }
+              ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_enum_variants() {
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub enum Foo {Foo1} }
+              fn main() { foo::Foo::Foo1<|> } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_const_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { const FOO: () = (); }
+              fn main() { foo::FOO<|> } ",
+            r"mod foo { <|>pub(crate) const FOO: () = (); }
+              fn main() { foo::FOO } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub const FOO: () = (); }
+              fn main() { foo::FOO<|> } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_static_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { static FOO: () = (); }
+              fn main() { foo::FOO<|> } ",
+            r"mod foo { <|>pub(crate) static FOO: () = (); }
+              fn main() { foo::FOO } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub static FOO: () = (); }
+              fn main() { foo::FOO<|> } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_trait_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { trait Foo { fn foo(&self) {} } }
+              fn main() { let x: &dyn foo::<|>Foo; } ",
+            r"mod foo { <|>pub(crate) trait Foo { fn foo(&self) {} } }
+              fn main() { let x: &dyn foo::Foo; } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub trait Foo { fn foo(&self) {} } }
+              fn main() { let x: &dyn foo::Foo<|>; } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_type_alias_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { type Foo = (); }
+              fn main() { let x: foo::Foo<|>; } ",
+            r"mod foo { <|>pub(crate) type Foo = (); }
+              fn main() { let x: foo::Foo; } ",
+        );
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub type Foo = (); }
+              fn main() { let x: foo::Foo<|>; } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_module_via_path() {
+        check_assist(
+            change_visibility,
+            r"mod foo { mod bar { fn bar() {} } }
+              fn main() { foo::bar<|>::bar(); } ",
+            r"mod foo { <|>pub(crate) mod bar { fn bar() {} } }
+              fn main() { foo::bar::bar(); } ",
+        );
+
+        check_assist(
+            change_visibility,
+            r"
+            //- /main.rs
+            mod foo;
+            fn main() { foo::bar<|>::baz(); }
+
+            //- /foo.rs
+            mod bar {
+                pub fn baz() {}
+            }
+            ",
+            r"<|>pub(crate) mod bar {
+    pub fn baz() {}
+}
+
+",
+        );
+
+        check_assist_not_applicable(
+            change_visibility,
+            r"mod foo { pub mod bar { pub fn bar() {} } }
+              fn main() { foo::bar<|>::bar(); } ",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_inline_module_in_other_file_via_path() {
+        check_assist(
+            change_visibility,
+            r"
+            //- /main.rs
+            mod foo;
+            fn main() { foo::bar<|>::baz(); }
+
+            //- /foo.rs
+            mod bar;
+
+            //- /foo/bar.rs
+            pub fn baz() {}
+            }
+            ",
+            r"<|>pub(crate) mod bar;
+",
+        );
+    }
+
+    #[test]
+    fn change_visibility_of_module_declaration_in_other_file_via_path() {
+        check_assist(
+            change_visibility,
+            r"//- /main.rs
+              mod foo;
+              fn main() { foo::bar<|>>::baz(); }
+
+              //- /foo.rs
+              mod bar {
+                  pub fn baz() {}
+              }",
+            r"<|>pub(crate) mod bar {
+    pub fn baz() {}
+}
+",
+        );
+    }
+
+    #[test]
+    #[ignore]
+    // FIXME handle reexports properly
+    fn change_visibility_of_reexport() {
+        check_assist(
+            change_visibility,
+            r"
+            mod foo {
+                use bar::Baz;
+                mod bar { pub(super) struct Baz; }
+            }
+            foo::Baz<|>
+            ",
+            r"
+            mod foo {
+                <|>pub(crate) use bar::Baz;
+                mod bar { pub(super) struct Baz; }
+            }
+            foo::Baz
+            ",
+        )
+    }
+
+    #[test]
+    fn adds_pub_when_target_is_in_another_crate() {
+        check_assist(
+            change_visibility,
+            r"//- /main.rs crate:a deps:foo
+              foo::Bar<|>
+              //- /lib.rs crate:foo
+              struct Bar;",
+            r"<|>pub struct Bar;
+",
+        )
+    }
+
+    #[test]
     fn change_visibility_target() {
         check_assist_target(change_visibility, "<|>fn foo() {}", "fn");
         check_assist_target(change_visibility, "pub(crate)<|> fn foo() {}", "pub(crate)");
diff --git a/crates/ra_db/src/fixture.rs b/crates/ra_db/src/fixture.rs
index 51d4c493e..f8f767091 100644
--- a/crates/ra_db/src/fixture.rs
+++ b/crates/ra_db/src/fixture.rs
@@ -2,7 +2,7 @@
 //! A fixture without metadata is parsed into a single source file.
 //! Use this to test functionality local to one file.
 //!
-//! Example:
+//! Simple Example:
 //! ```
 //! r#"
 //! fn main() {
@@ -15,7 +15,7 @@
 //! The basic form is specifying filenames,
 //! which is also how to define multiple files in a single test fixture
 //!
-//! Example:
+//! Example using two files in the same crate:
 //! ```
 //! "
 //! //- /main.rs
@@ -29,6 +29,20 @@
 //! "
 //! ```
 //!
+//! Example using two crates with one file each, with one crate depending on the other:
+//! ```
+//! r#"
+//! //- /main.rs crate:a deps:b
+//! fn main() {
+//!     b::foo();
+//! }
+//! //- /lib.rs crate:b
+//! pub fn b() {
+//!     println!("Hello World")
+//! }
+//! "#
+//! ```
+//!
 //! Metadata allows specifying all settings and variables
 //! that are available in a real rust project:
 //! - crate names via `crate:cratename`
@@ -36,7 +50,7 @@
 //! - configuration settings via `cfg:dbg=false,opt_level=2`
 //! - environment variables via `env:PATH=/bin,RUST_LOG=debug`
 //!
-//! Example:
+//! Example using all available metadata:
 //! ```
 //! "
 //! //- /lib.rs crate:foo deps:bar,baz cfg:foo=a,bar=b env:OUTDIR=path/to,OTHER=foo
diff --git a/crates/ra_flycheck/Cargo.toml b/crates/ra_flycheck/Cargo.toml
index eac502da5..1aa39bade 100644
--- a/crates/ra_flycheck/Cargo.toml
+++ b/crates/ra_flycheck/Cargo.toml
@@ -9,12 +9,8 @@ doctest = false
 
 [dependencies]
 crossbeam-channel = "0.4.0"
-lsp-types = { version = "0.74.0", features = ["proposed"] }
 log = "0.4.8"
 cargo_metadata = "0.10.0"
 serde_json = "1.0.48"
 jod-thread = "0.1.1"
 ra_toolchain = { path = "../ra_toolchain" }
-
-[dev-dependencies]
-insta = "0.16.0"
diff --git a/crates/ra_flycheck/src/conv.rs b/crates/ra_flycheck/src/conv.rs
deleted file mode 100644
index 817543deb..000000000
--- a/crates/ra_flycheck/src/conv.rs
+++ /dev/null
@@ -1,341 +0,0 @@
-//! This module provides the functionality needed to convert diagnostics from
-//! `cargo check` json format to the LSP diagnostic format.
-use cargo_metadata::diagnostic::{
-    Applicability, Diagnostic as RustDiagnostic, DiagnosticLevel, DiagnosticSpan,
-    DiagnosticSpanMacroExpansion,
-};
-use lsp_types::{
-    CodeAction, Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag,
-    Location, NumberOrString, Position, Range, TextEdit, Url, WorkspaceEdit,
-};
-use std::{
-    collections::HashMap,
-    fmt::Write,
-    path::{Component, Path, PathBuf, Prefix},
-    str::FromStr,
-};
-
-#[cfg(test)]
-mod test;
-
-/// Converts a Rust level string to a LSP severity
-fn map_level_to_severity(val: DiagnosticLevel) -> Option<DiagnosticSeverity> {
-    match val {
-        DiagnosticLevel::Ice => Some(DiagnosticSeverity::Error),
-        DiagnosticLevel::Error => Some(DiagnosticSeverity::Error),
-        DiagnosticLevel::Warning => Some(DiagnosticSeverity::Warning),
-        DiagnosticLevel::Note => Some(DiagnosticSeverity::Information),
-        DiagnosticLevel::Help => Some(DiagnosticSeverity::Hint),
-        DiagnosticLevel::Unknown => None,
-    }
-}
-
-/// Check whether a file name is from macro invocation
-fn is_from_macro(file_name: &str) -> bool {
-    file_name.starts_with('<') && file_name.ends_with('>')
-}
-
-/// Converts a Rust macro span to a LSP location recursively
-fn map_macro_span_to_location(
-    span_macro: &DiagnosticSpanMacroExpansion,
-    workspace_root: &PathBuf,
-) -> Option<Location> {
-    if !is_from_macro(&span_macro.span.file_name) {
-        return Some(map_span_to_location(&span_macro.span, workspace_root));
-    }
-
-    if let Some(expansion) = &span_macro.span.expansion {
-        return map_macro_span_to_location(&expansion, workspace_root);
-    }
-
-    None
-}
-
-/// Converts a Rust span to a LSP location, resolving macro expansion site if neccesary
-fn map_span_to_location(span: &DiagnosticSpan, workspace_root: &PathBuf) -> Location {
-    if span.expansion.is_some() {
-        let expansion = span.expansion.as_ref().unwrap();
-        if let Some(macro_range) = map_macro_span_to_location(&expansion, workspace_root) {
-            return macro_range;
-        }
-    }
-
-    map_span_to_location_naive(span, workspace_root)
-}
-
-/// Converts a Rust span to a LSP location
-fn map_span_to_location_naive(span: &DiagnosticSpan, workspace_root: &PathBuf) -> Location {
-    let mut file_name = workspace_root.clone();
-    file_name.push(&span.file_name);
-    let uri = url_from_path_with_drive_lowercasing(file_name).unwrap();
-
-    let range = Range::new(
-        Position::new(span.line_start as u64 - 1, span.column_start as u64 - 1),
-        Position::new(span.line_end as u64 - 1, span.column_end as u64 - 1),
-    );
-
-    Location { uri, range }
-}
-
-/// Converts a secondary Rust span to a LSP related information
-///
-/// If the span is unlabelled this will return `None`.
-fn map_secondary_span_to_related(
-    span: &DiagnosticSpan,
-    workspace_root: &PathBuf,
-) -> Option<DiagnosticRelatedInformation> {
-    if let Some(label) = &span.label {
-        let location = map_span_to_location(span, workspace_root);
-        Some(DiagnosticRelatedInformation { location, message: label.clone() })
-    } else {
-        // Nothing to label this with
-        None
-    }
-}
-
-/// Determines if diagnostic is related to unused code
-fn is_unused_or_unnecessary(rd: &RustDiagnostic) -> bool {
-    if let Some(code) = &rd.code {
-        match code.code.as_str() {
-            "dead_code" | "unknown_lints" | "unreachable_code" | "unused_attributes"
-            | "unused_imports" | "unused_macros" | "unused_variables" => true,
-            _ => false,
-        }
-    } else {
-        false
-    }
-}
-
-/// Determines if diagnostic is related to deprecated code
-fn is_deprecated(rd: &RustDiagnostic) -> bool {
-    if let Some(code) = &rd.code {
-        match code.code.as_str() {
-            "deprecated" => true,
-            _ => false,
-        }
-    } else {
-        false
-    }
-}
-
-enum MappedRustChildDiagnostic {
-    Related(DiagnosticRelatedInformation),
-    SuggestedFix(CodeAction),
-    MessageLine(String),
-}
-
-fn map_rust_child_diagnostic(
-    rd: &RustDiagnostic,
-    workspace_root: &PathBuf,
-) -> MappedRustChildDiagnostic {
-    let spans: Vec<&DiagnosticSpan> = rd.spans.iter().filter(|s| s.is_primary).collect();
-    if spans.is_empty() {
-        // `rustc` uses these spanless children as a way to print multi-line
-        // messages
-        return MappedRustChildDiagnostic::MessageLine(rd.message.clone());
-    }
-
-    let mut edit_map: HashMap<Url, Vec<TextEdit>> = HashMap::new();
-    for &span in &spans {
-        match (&span.suggestion_applicability, &span.suggested_replacement) {
-            (Some(Applicability::MachineApplicable), Some(suggested_replacement)) => {
-                let location = map_span_to_location(span, workspace_root);
-                let edit = TextEdit::new(location.range, suggested_replacement.clone());
-                edit_map.entry(location.uri).or_default().push(edit);
-            }
-            _ => {}
-        }
-    }
-
-    if !edit_map.is_empty() {
-        MappedRustChildDiagnostic::SuggestedFix(CodeAction {
-            title: rd.message.clone(),
-            kind: Some("quickfix".to_string()),
-            diagnostics: None,
-            edit: Some(WorkspaceEdit::new(edit_map)),
-            command: None,
-            is_preferred: None,
-        })
-    } else {
-        MappedRustChildDiagnostic::Related(DiagnosticRelatedInformation {
-            location: map_span_to_location(spans[0], workspace_root),
-            message: rd.message.clone(),
-        })
-    }
-}
-
-#[derive(Debug)]
-pub(crate) struct MappedRustDiagnostic {
-    pub location: Location,
-    pub diagnostic: Diagnostic,
-    pub fixes: Vec<CodeAction>,
-}
-
-/// Converts a Rust root diagnostic to LSP form
-///
-/// This flattens the Rust diagnostic by:
-///
-/// 1. Creating a LSP diagnostic with the root message and primary span.
-/// 2. Adding any labelled secondary spans to `relatedInformation`
-/// 3. Categorising child diagnostics as either `SuggestedFix`es,
-///    `relatedInformation` or additional message lines.
-///
-/// If the diagnostic has no primary span this will return `None`
-pub(crate) fn map_rust_diagnostic_to_lsp(
-    rd: &RustDiagnostic,
-    workspace_root: &PathBuf,
-) -> Vec<MappedRustDiagnostic> {
-    let primary_spans: Vec<&DiagnosticSpan> = rd.spans.iter().filter(|s| s.is_primary).collect();
-    if primary_spans.is_empty() {
-        return vec![];
-    }
-
-    let severity = map_level_to_severity(rd.level);
-
-    let mut source = String::from("rustc");
-    let mut code = rd.code.as_ref().map(|c| c.code.clone());
-    if let Some(code_val) = &code {
-        // See if this is an RFC #2103 scoped lint (e.g. from Clippy)
-        let scoped_code: Vec<&str> = code_val.split("::").collect();
-        if scoped_code.len() == 2 {
-            source = String::from(scoped_code[0]);
-            code = Some(String::from(scoped_code[1]));
-        }
-    }
-
-    let mut needs_primary_span_label = true;
-    let mut related_information = vec![];
-    let mut tags = vec![];
-
-    for secondary_span in rd.spans.iter().filter(|s| !s.is_primary) {
-        let related = map_secondary_span_to_related(secondary_span, workspace_root);
-        if let Some(related) = related {
-            related_information.push(related);
-        }
-    }
-
-    let mut fixes = vec![];
-    let mut message = rd.message.clone();
-    for child in &rd.children {
-        let child = map_rust_child_diagnostic(&child, workspace_root);
-        match child {
-            MappedRustChildDiagnostic::Related(related) => related_information.push(related),
-            MappedRustChildDiagnostic::SuggestedFix(code_action) => fixes.push(code_action),
-            MappedRustChildDiagnostic::MessageLine(message_line) => {
-                write!(&mut message, "\n{}", message_line).unwrap();
-
-                // These secondary messages usually duplicate the content of the
-                // primary span label.
-                needs_primary_span_label = false;
-            }
-        }
-    }
-
-    if is_unused_or_unnecessary(rd) {
-        tags.push(DiagnosticTag::Unnecessary);
-    }
-
-    if is_deprecated(rd) {
-        tags.push(DiagnosticTag::Deprecated);
-    }
-
-    primary_spans
-        .iter()
-        .map(|primary_span| {
-            let location = map_span_to_location(&primary_span, workspace_root);
-
-            let mut message = message.clone();
-            if needs_primary_span_label {
-                if let Some(primary_span_label) = &primary_span.label {
-                    write!(&mut message, "\n{}", primary_span_label).unwrap();
-                }
-            }
-
-            // If error occurs from macro expansion, add related info pointing to
-            // where the error originated
-            if !is_from_macro(&primary_span.file_name) && primary_span.expansion.is_some() {
-                let def_loc = map_span_to_location_naive(&primary_span, workspace_root);
-                related_information.push(DiagnosticRelatedInformation {
-                    location: def_loc,
-                    message: "Error originated from macro here".to_string(),
-                });
-            }
-
-            let diagnostic = Diagnostic {
-                range: location.range,
-                severity,
-                code: code.clone().map(NumberOrString::String),
-                source: Some(source.clone()),
-                message,
-                related_information: if !related_information.is_empty() {
-                    Some(related_information.clone())
-                } else {
-                    None
-                },
-                tags: if !tags.is_empty() { Some(tags.clone()) } else { None },
-            };
-
-            MappedRustDiagnostic { location, diagnostic, fixes: fixes.clone() }
-        })
-        .collect()
-}
-
-/// Returns a `Url` object from a given path, will lowercase drive letters if present.
-/// This will only happen when processing windows paths.
-///
-/// When processing non-windows path, this is essentially the same as `Url::from_file_path`.
-pub fn url_from_path_with_drive_lowercasing(
-    path: impl AsRef<Path>,
-) -> Result<Url, Box<dyn std::error::Error + Send + Sync>> {
-    let component_has_windows_drive = path.as_ref().components().any(|comp| {
-        if let Component::Prefix(c) = comp {
-            match c.kind() {
-                Prefix::Disk(_) | Prefix::VerbatimDisk(_) => return true,
-                _ => return false,
-            }
-        }
-        false
-    });
-
-    // VSCode expects drive letters to be lowercased, where rust will uppercase the drive letters.
-    if component_has_windows_drive {
-        let url_original = Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?;
-
-        let drive_partition: Vec<&str> = url_original.as_str().rsplitn(2, ':').collect();
-
-        // There is a drive partition, but we never found a colon.
-        // This should not happen, but in this case we just pass it through.
-        if drive_partition.len() == 1 {
-            return Ok(url_original);
-        }
-
-        let joined = drive_partition[1].to_ascii_lowercase() + ":" + drive_partition[0];
-        let url = Url::from_str(&joined).expect("This came from a valid `Url`");
-
-        Ok(url)
-    } else {
-        Ok(Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?)
-    }
-}
-
-// `Url` is not able to parse windows paths on unix machines.
-#[cfg(target_os = "windows")]
-#[cfg(test)]
-mod path_conversion_windows_tests {
-    use super::url_from_path_with_drive_lowercasing;
-    #[test]
-    fn test_lowercase_drive_letter_with_drive() {
-        let url = url_from_path_with_drive_lowercasing("C:\\Test").unwrap();
-
-        assert_eq!(url.to_string(), "file:///c:/Test");
-    }
-
-    #[test]
-    fn test_drive_without_colon_passthrough() {
-        let url = url_from_path_with_drive_lowercasing(r#"\\localhost\C$\my_dir"#).unwrap();
-
-        assert_eq!(url.to_string(), "file://localhost/C$/my_dir");
-    }
-}
diff --git a/crates/ra_flycheck/src/conv/test.rs b/crates/ra_flycheck/src/conv/test.rs
deleted file mode 100644
index 4e81455ca..000000000
--- a/crates/ra_flycheck/src/conv/test.rs
+++ /dev/null
@@ -1,1072 +0,0 @@
-//! This module contains the large and verbose snapshot tests for the
-//! conversions between `cargo check` json and LSP diagnostics.
-#[cfg(not(windows))]
-use crate::*;
-
-#[cfg(not(windows))]
-fn parse_diagnostic(val: &str) -> cargo_metadata::diagnostic::Diagnostic {
-    serde_json::from_str::<cargo_metadata::diagnostic::Diagnostic>(val).unwrap()
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_rustc_incompatible_type_for_trait() {
-    let diag = parse_diagnostic(
-        r##"{
-            "message": "method `next` has an incompatible type for trait",
-            "code": {
-                "code": "E0053",
-                "explanation": "\nThe parameters of any trait method must match between a trait implementation\nand the trait definition.\n\nHere are a couple examples of this error:\n\n```compile_fail,E0053\ntrait Foo {\n    fn foo(x: u16);\n    fn bar(&self);\n}\n\nstruct Bar;\n\nimpl Foo for Bar {\n    // error, expected u16, found i16\n    fn foo(x: i16) { }\n\n    // error, types differ in mutability\n    fn bar(&mut self) { }\n}\n```\n"
-            },
-            "level": "error",
-            "spans": [
-                {
-                    "file_name": "compiler/ty/list_iter.rs",
-                    "byte_start": 1307,
-                    "byte_end": 1350,
-                    "line_start": 52,
-                    "line_end": 52,
-                    "column_start": 5,
-                    "column_end": 48,
-                    "is_primary": true,
-                    "text": [
-                        {
-                            "text": "    fn next(&self) -> Option<&'list ty::Ref<M>> {",
-                            "highlight_start": 5,
-                            "highlight_end": 48
-                        }
-                    ],
-                    "label": "types differ in mutability",
-                    "suggested_replacement": null,
-                    "suggestion_applicability": null,
-                    "expansion": null
-                }
-            ],
-            "children": [
-                {
-                    "message": "expected type `fn(&mut ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&ty::Ref<M>>`\n   found type `fn(&ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&'list ty::Ref<M>>`",
-                    "code": null,
-                    "level": "note",
-                    "spans": [],
-                    "children": [],
-                    "rendered": null
-                }
-            ],
-            "rendered": "error[E0053]: method `next` has an incompatible type for trait\n  --> compiler/ty/list_iter.rs:52:5\n   |\n52 |     fn next(&self) -> Option<&'list ty::Ref<M>> {\n   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ types differ in mutability\n   |\n   = note: expected type `fn(&mut ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&ty::Ref<M>>`\n              found type `fn(&ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&'list ty::Ref<M>>`\n\n"
-        }
-        "##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_rustc_unused_variable() {
-    let diag = parse_diagnostic(
-        r##"{
-"message": "unused variable: `foo`",
-"code": {
-    "code": "unused_variables",
-    "explanation": null
-},
-"level": "warning",
-"spans": [
-    {
-        "file_name": "driver/subcommand/repl.rs",
-        "byte_start": 9228,
-        "byte_end": 9231,
-        "line_start": 291,
-        "line_end": 291,
-        "column_start": 9,
-        "column_end": 12,
-        "is_primary": true,
-        "text": [
-            {
-                "text": "    let foo = 42;",
-                "highlight_start": 9,
-                "highlight_end": 12
-            }
-        ],
-        "label": null,
-        "suggested_replacement": null,
-        "suggestion_applicability": null,
-        "expansion": null
-    }
-],
-"children": [
-    {
-        "message": "#[warn(unused_variables)] on by default",
-        "code": null,
-        "level": "note",
-        "spans": [],
-        "children": [],
-        "rendered": null
-    },
-    {
-        "message": "consider prefixing with an underscore",
-        "code": null,
-        "level": "help",
-        "spans": [
-            {
-                "file_name": "driver/subcommand/repl.rs",
-                "byte_start": 9228,
-                "byte_end": 9231,
-                "line_start": 291,
-                "line_end": 291,
-                "column_start": 9,
-                "column_end": 12,
-                "is_primary": true,
-                "text": [
-                    {
-                        "text": "    let foo = 42;",
-                        "highlight_start": 9,
-                        "highlight_end": 12
-                    }
-                ],
-                "label": null,
-                "suggested_replacement": "_foo",
-                "suggestion_applicability": "MachineApplicable",
-                "expansion": null
-            }
-        ],
-        "children": [],
-        "rendered": null
-    }
-],
-"rendered": "warning: unused variable: `foo`\n   --> driver/subcommand/repl.rs:291:9\n    |\n291 |     let foo = 42;\n    |         ^^^ help: consider prefixing with an underscore: `_foo`\n    |\n    = note: #[warn(unused_variables)] on by default\n\n"
-}"##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_rustc_wrong_number_of_parameters() {
-    let diag = parse_diagnostic(
-        r##"{
-"message": "this function takes 2 parameters but 3 parameters were supplied",
-"code": {
-    "code": "E0061",
-    "explanation": "\nThe number of arguments passed to a function must match the number of arguments\nspecified in the function signature.\n\nFor example, a function like:\n\n```\nfn f(a: u16, b: &str) {}\n```\n\nMust always be called with exactly two arguments, e.g., `f(2, \"test\")`.\n\nNote that Rust does not have a notion of optional function arguments or\nvariadic functions (except for its C-FFI).\n"
-},
-"level": "error",
-"spans": [
-    {
-        "file_name": "compiler/ty/select.rs",
-        "byte_start": 8787,
-        "byte_end": 9241,
-        "line_start": 219,
-        "line_end": 231,
-        "column_start": 5,
-        "column_end": 6,
-        "is_primary": false,
-        "text": [
-            {
-                "text": "    pub fn add_evidence(",
-                "highlight_start": 5,
-                "highlight_end": 25
-            },
-            {
-                "text": "        &mut self,",
-                "highlight_start": 1,
-                "highlight_end": 19
-            },
-            {
-                "text": "        target_poly: &ty::Ref<ty::Poly>,",
-                "highlight_start": 1,
-                "highlight_end": 41
-            },
-            {
-                "text": "        evidence_poly: &ty::Ref<ty::Poly>,",
-                "highlight_start": 1,
-                "highlight_end": 43
-            },
-            {
-                "text": "    ) {",
-                "highlight_start": 1,
-                "highlight_end": 8
-            },
-            {
-                "text": "        match target_poly {",
-                "highlight_start": 1,
-                "highlight_end": 28
-            },
-            {
-                "text": "            ty::Ref::Var(tvar, _) => self.add_var_evidence(tvar, evidence_poly),",
-                "highlight_start": 1,
-                "highlight_end": 81
-            },
-            {
-                "text": "            ty::Ref::Fixed(target_ty) => {",
-                "highlight_start": 1,
-                "highlight_end": 43
-            },
-            {
-                "text": "                let evidence_ty = evidence_poly.resolve_to_ty();",
-                "highlight_start": 1,
-                "highlight_end": 65
-            },
-            {
-                "text": "                self.add_evidence_ty(target_ty, evidence_poly, evidence_ty)",
-                "highlight_start": 1,
-                "highlight_end": 76
-            },
-            {
-                "text": "            }",
-                "highlight_start": 1,
-                "highlight_end": 14
-            },
-            {
-                "text": "        }",
-                "highlight_start": 1,
-                "highlight_end": 10
-            },
-            {
-                "text": "    }",
-                "highlight_start": 1,
-                "highlight_end": 6
-            }
-        ],
-        "label": "defined here",
-        "suggested_replacement": null,
-        "suggestion_applicability": null,
-        "expansion": null
-    },
-    {
-        "file_name": "compiler/ty/select.rs",
-        "byte_start": 4045,
-        "byte_end": 4057,
-        "line_start": 104,
-        "line_end": 104,
-        "column_start": 18,
-        "column_end": 30,
-        "is_primary": true,
-        "text": [
-            {
-                "text": "            self.add_evidence(target_fixed, evidence_fixed, false);",
-                "highlight_start": 18,
-                "highlight_end": 30
-            }
-        ],
-        "label": "expected 2 parameters",
-        "suggested_replacement": null,
-        "suggestion_applicability": null,
-        "expansion": null
-    }
-],
-"children": [],
-"rendered": "error[E0061]: this function takes 2 parameters but 3 parameters were supplied\n   --> compiler/ty/select.rs:104:18\n    |\n104 |               self.add_evidence(target_fixed, evidence_fixed, false);\n    |                    ^^^^^^^^^^^^ expected 2 parameters\n...\n219 | /     pub fn add_evidence(\n220 | |         &mut self,\n221 | |         target_poly: &ty::Ref<ty::Poly>,\n222 | |         evidence_poly: &ty::Ref<ty::Poly>,\n...   |\n230 | |         }\n231 | |     }\n    | |_____- defined here\n\n"
-}"##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_clippy_pass_by_ref() {
-    let diag = parse_diagnostic(
-        r##"{
-"message": "this argument is passed by reference, but would be more efficient if passed by value",
-"code": {
-    "code": "clippy::trivially_copy_pass_by_ref",
-    "explanation": null
-},
-"level": "warning",
-"spans": [
-    {
-        "file_name": "compiler/mir/tagset.rs",
-        "byte_start": 941,
-        "byte_end": 946,
-        "line_start": 42,
-        "line_end": 42,
-        "column_start": 24,
-        "column_end": 29,
-        "is_primary": true,
-        "text": [
-            {
-                "text": "    pub fn is_disjoint(&self, other: Self) -> bool {",
-                "highlight_start": 24,
-                "highlight_end": 29
-            }
-        ],
-        "label": null,
-        "suggested_replacement": null,
-        "suggestion_applicability": null,
-        "expansion": null
-    }
-],
-"children": [
-    {
-        "message": "lint level defined here",
-        "code": null,
-        "level": "note",
-        "spans": [
-            {
-                "file_name": "compiler/lib.rs",
-                "byte_start": 8,
-                "byte_end": 19,
-                "line_start": 1,
-                "line_end": 1,
-                "column_start": 9,
-                "column_end": 20,
-                "is_primary": true,
-                "text": [
-                    {
-                        "text": "#![warn(clippy::all)]",
-                        "highlight_start": 9,
-                        "highlight_end": 20
-                    }
-                ],
-                "label": null,
-                "suggested_replacement": null,
-                "suggestion_applicability": null,
-                "expansion": null
-            }
-        ],
-        "children": [],
-        "rendered": null
-    },
-    {
-        "message": "#[warn(clippy::trivially_copy_pass_by_ref)] implied by #[warn(clippy::all)]",
-        "code": null,
-        "level": "note",
-        "spans": [],
-        "children": [],
-        "rendered": null
-    },
-    {
-        "message": "for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref",
-        "code": null,
-        "level": "help",
-        "spans": [],
-        "children": [],
-        "rendered": null
-    },
-    {
-        "message": "consider passing by value instead",
-        "code": null,
-        "level": "help",
-        "spans": [
-            {
-                "file_name": "compiler/mir/tagset.rs",
-                "byte_start": 941,
-                "byte_end": 946,
-                "line_start": 42,
-                "line_end": 42,
-                "column_start": 24,
-                "column_end": 29,
-                "is_primary": true,
-                "text": [
-                    {
-                        "text": "    pub fn is_disjoint(&self, other: Self) -> bool {",
-                        "highlight_start": 24,
-                        "highlight_end": 29
-                    }
-                ],
-                "label": null,
-                "suggested_replacement": "self",
-                "suggestion_applicability": "Unspecified",
-                "expansion": null
-            }
-        ],
-        "children": [],
-        "rendered": null
-    }
-],
-"rendered": "warning: this argument is passed by reference, but would be more efficient if passed by value\n  --> compiler/mir/tagset.rs:42:24\n   |\n42 |     pub fn is_disjoint(&self, other: Self) -> bool {\n   |                        ^^^^^ help: consider passing by value instead: `self`\n   |\nnote: lint level defined here\n  --> compiler/lib.rs:1:9\n   |\n1  | #![warn(clippy::all)]\n   |         ^^^^^^^^^^^\n   = note: #[warn(clippy::trivially_copy_pass_by_ref)] implied by #[warn(clippy::all)]\n   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref\n\n"
-}"##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_rustc_mismatched_type() {
-    let diag = parse_diagnostic(
-        r##"{
-"message": "mismatched types",
-"code": {
-    "code": "E0308",
-    "explanation": "\nThis error occurs when the compiler was unable to infer the concrete type of a\nvariable. It can occur for several cases, the most common of which is a\nmismatch in the expected type that the compiler inferred for a variable's\ninitializing expression, and the actual type explicitly assigned to the\nvariable.\n\nFor example:\n\n```compile_fail,E0308\nlet x: i32 = \"I am not a number!\";\n//     ~~~   ~~~~~~~~~~~~~~~~~~~~\n//      |             |\n//      |    initializing expression;\n//      |    compiler infers type `&str`\n//      |\n//    type `i32` assigned to variable `x`\n```\n"
-},
-"level": "error",
-"spans": [
-    {
-        "file_name": "runtime/compiler_support.rs",
-        "byte_start": 1589,
-        "byte_end": 1594,
-        "line_start": 48,
-        "line_end": 48,
-        "column_start": 65,
-        "column_end": 70,
-        "is_primary": true,
-        "text": [
-            {
-                "text": "    let layout = alloc::Layout::from_size_align_unchecked(size, align);",
-                "highlight_start": 65,
-                "highlight_end": 70
-            }
-        ],
-        "label": "expected usize, found u32",
-        "suggested_replacement": null,
-        "suggestion_applicability": null,
-        "expansion": null
-    }
-],
-"children": [],
-"rendered": "error[E0308]: mismatched types\n  --> runtime/compiler_support.rs:48:65\n   |\n48 |     let layout = alloc::Layout::from_size_align_unchecked(size, align);\n   |                                                                 ^^^^^ expected usize, found u32\n\n"
-}"##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_handles_macro_location() {
-    let diag = parse_diagnostic(
-        r##"{
-"rendered": "error[E0277]: can't compare `{integer}` with `&str`\n --> src/main.rs:2:5\n  |\n2 |     assert_eq!(1, \"love\");\n  |     ^^^^^^^^^^^^^^^^^^^^^^ no implementation for `{integer} == &str`\n  |\n  = help: the trait `std::cmp::PartialEq<&str>` is not implemented for `{integer}`\n  = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)\n\n",
-"children": [
-    {
-        "children": [],
-        "code": null,
-        "level": "help",
-        "message": "the trait `std::cmp::PartialEq<&str>` is not implemented for `{integer}`",
-        "rendered": null,
-        "spans": []
-    }
-],
-"code": {
-    "code": "E0277",
-    "explanation": "\nYou tried to use a type which doesn't implement some trait in a place which\nexpected that trait. Erroneous code example:\n\n```compile_fail,E0277\n// here we declare the Foo trait with a bar method\ntrait Foo {\n    fn bar(&self);\n}\n\n// we now declare a function which takes an object implementing the Foo trait\nfn some_func<T: Foo>(foo: T) {\n    foo.bar();\n}\n\nfn main() {\n    // we now call the method with the i32 type, which doesn't implement\n    // the Foo trait\n    some_func(5i32); // error: the trait bound `i32 : Foo` is not satisfied\n}\n```\n\nIn order to fix this error, verify that the type you're using does implement\nthe trait. Example:\n\n```\ntrait Foo {\n    fn bar(&self);\n}\n\nfn some_func<T: Foo>(foo: T) {\n    foo.bar(); // we can now use this method since i32 implements the\n               // Foo trait\n}\n\n// we implement the trait on the i32 type\nimpl Foo for i32 {\n    fn bar(&self) {}\n}\n\nfn main() {\n    some_func(5i32); // ok!\n}\n```\n\nOr in a generic context, an erroneous code example would look like:\n\n```compile_fail,E0277\nfn some_func<T>(foo: T) {\n    println!(\"{:?}\", foo); // error: the trait `core::fmt::Debug` is not\n                           //        implemented for the type `T`\n}\n\nfn main() {\n    // We now call the method with the i32 type,\n    // which *does* implement the Debug trait.\n    some_func(5i32);\n}\n```\n\nNote that the error here is in the definition of the generic function: Although\nwe only call it with a parameter that does implement `Debug`, the compiler\nstill rejects the function: It must work with all possible input types. In\norder to make this example compile, we need to restrict the generic type we're\naccepting:\n\n```\nuse std::fmt;\n\n// Restrict the input type to types that implement Debug.\nfn some_func<T: fmt::Debug>(foo: T) {\n    println!(\"{:?}\", foo);\n}\n\nfn main() {\n    // Calling the method is still fine, as i32 implements Debug.\n    some_func(5i32);\n\n    // This would fail to compile now:\n    // struct WithoutDebug;\n    // some_func(WithoutDebug);\n}\n```\n\nRust only looks at the signature of the called function, as such it must\nalready specify all requirements that will be used for every type parameter.\n"
-},
-"level": "error",
-"message": "can't compare `{integer}` with `&str`",
-"spans": [
-    {
-        "byte_end": 155,
-        "byte_start": 153,
-        "column_end": 33,
-        "column_start": 31,
-        "expansion": {
-            "def_site_span": {
-                "byte_end": 940,
-                "byte_start": 0,
-                "column_end": 6,
-                "column_start": 1,
-                "expansion": null,
-                "file_name": "<::core::macros::assert_eq macros>",
-                "is_primary": false,
-                "label": null,
-                "line_end": 36,
-                "line_start": 1,
-                "suggested_replacement": null,
-                "suggestion_applicability": null,
-                "text": [
-                    {
-                        "highlight_end": 35,
-                        "highlight_start": 1,
-                        "text": "($ left : expr, $ right : expr) =>"
-                    },
-                    {
-                        "highlight_end": 3,
-                        "highlight_start": 1,
-                        "text": "({"
-                    },
-                    {
-                        "highlight_end": 33,
-                        "highlight_start": 1,
-                        "text": "     match (& $ left, & $ right)"
-                    },
-                    {
-                        "highlight_end": 7,
-                        "highlight_start": 1,
-                        "text": "     {"
-                    },
-                    {
-                        "highlight_end": 34,
-                        "highlight_start": 1,
-                        "text": "         (left_val, right_val) =>"
-                    },
-                    {
-                        "highlight_end": 11,
-                        "highlight_start": 1,
-                        "text": "         {"
-                    },
-                    {
-                        "highlight_end": 46,
-                        "highlight_start": 1,
-                        "text": "             if ! (* left_val == * right_val)"
-                    },
-                    {
-                        "highlight_end": 15,
-                        "highlight_start": 1,
-                        "text": "             {"
-                    },
-                    {
-                        "highlight_end": 25,
-                        "highlight_start": 1,
-                        "text": "                 panic !"
-                    },
-                    {
-                        "highlight_end": 57,
-                        "highlight_start": 1,
-                        "text": "                 (r#\"assertion failed: `(left == right)`"
-                    },
-                    {
-                        "highlight_end": 16,
-                        "highlight_start": 1,
-                        "text": "  left: `{:?}`,"
-                    },
-                    {
-                        "highlight_end": 18,
-                        "highlight_start": 1,
-                        "text": " right: `{:?}`\"#,"
-                    },
-                    {
-                        "highlight_end": 47,
-                        "highlight_start": 1,
-                        "text": "                  & * left_val, & * right_val)"
-                    },
-                    {
-                        "highlight_end": 15,
-                        "highlight_start": 1,
-                        "text": "             }"
-                    },
-                    {
-                        "highlight_end": 11,
-                        "highlight_start": 1,
-                        "text": "         }"
-                    },
-                    {
-                        "highlight_end": 7,
-                        "highlight_start": 1,
-                        "text": "     }"
-                    },
-                    {
-                        "highlight_end": 42,
-                        "highlight_start": 1,
-                        "text": " }) ; ($ left : expr, $ right : expr,) =>"
-                    },
-                    {
-                        "highlight_end": 49,
-                        "highlight_start": 1,
-                        "text": "({ $ crate :: assert_eq ! ($ left, $ right) }) ;"
-                    },
-                    {
-                        "highlight_end": 53,
-                        "highlight_start": 1,
-                        "text": "($ left : expr, $ right : expr, $ ($ arg : tt) +) =>"
-                    },
-                    {
-                        "highlight_end": 3,
-                        "highlight_start": 1,
-                        "text": "({"
-                    },
-                    {
-                        "highlight_end": 37,
-                        "highlight_start": 1,
-                        "text": "     match (& ($ left), & ($ right))"
-                    },
-                    {
-                        "highlight_end": 7,
-                        "highlight_start": 1,
-                        "text": "     {"
-                    },
-                    {
-                        "highlight_end": 34,
-                        "highlight_start": 1,
-                        "text": "         (left_val, right_val) =>"
-                    },
-                    {
-                        "highlight_end": 11,
-                        "highlight_start": 1,
-                        "text": "         {"
-                    },
-                    {
-                        "highlight_end": 46,
-                        "highlight_start": 1,
-                        "text": "             if ! (* left_val == * right_val)"
-                    },
-                    {
-                        "highlight_end": 15,
-                        "highlight_start": 1,
-                        "text": "             {"
-                    },
-                    {
-                        "highlight_end": 25,
-                        "highlight_start": 1,
-                        "text": "                 panic !"
-                    },
-                    {
-                        "highlight_end": 57,
-                        "highlight_start": 1,
-                        "text": "                 (r#\"assertion failed: `(left == right)`"
-                    },
-                    {
-                        "highlight_end": 16,
-                        "highlight_start": 1,
-                        "text": "  left: `{:?}`,"
-                    },
-                    {
-                        "highlight_end": 22,
-                        "highlight_start": 1,
-                        "text": " right: `{:?}`: {}\"#,"
-                    },
-                    {
-                        "highlight_end": 72,
-                        "highlight_start": 1,
-                        "text": "                  & * left_val, & * right_val, $ crate :: format_args !"
-                    },
-                    {
-                        "highlight_end": 33,
-                        "highlight_start": 1,
-                        "text": "                  ($ ($ arg) +))"
-                    },
-                    {
-                        "highlight_end": 15,
-                        "highlight_start": 1,
-                        "text": "             }"
-                    },
-                    {
-                        "highlight_end": 11,
-                        "highlight_start": 1,
-                        "text": "         }"
-                    },
-                    {
-                        "highlight_end": 7,
-                        "highlight_start": 1,
-                        "text": "     }"
-                    },
-                    {
-                        "highlight_end": 6,
-                        "highlight_start": 1,
-                        "text": " }) ;"
-                    }
-                ]
-            },
-            "macro_decl_name": "assert_eq!",
-            "span": {
-                "byte_end": 38,
-                "byte_start": 16,
-                "column_end": 27,
-                "column_start": 5,
-                "expansion": null,
-                "file_name": "src/main.rs",
-                "is_primary": false,
-                "label": null,
-                "line_end": 2,
-                "line_start": 2,
-                "suggested_replacement": null,
-                "suggestion_applicability": null,
-                "text": [
-                    {
-                        "highlight_end": 27,
-                        "highlight_start": 5,
-                        "text": "    assert_eq!(1, \"love\");"
-                    }
-                ]
-            }
-        },
-        "file_name": "<::core::macros::assert_eq macros>",
-        "is_primary": true,
-        "label": "no implementation for `{integer} == &str`",
-        "line_end": 7,
-        "line_start": 7,
-        "suggested_replacement": null,
-        "suggestion_applicability": null,
-        "text": [
-            {
-                "highlight_end": 33,
-                "highlight_start": 31,
-                "text": "             if ! (* left_val == * right_val)"
-            }
-        ]
-    }
-]
-}"##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_macro_compiler_error() {
-    let diag = parse_diagnostic(
-        r##"{
-    "rendered": "error: Please register your known path in the path module\n   --> crates/ra_hir_def/src/path.rs:265:9\n    |\n265 |         compile_error!(\"Please register your known path in the path module\")\n    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n    | \n   ::: crates/ra_hir_def/src/data.rs:80:16\n    |\n80  |     let path = path![std::future::Future];\n    |                -------------------------- in this macro invocation\n\n",
-    "children": [],
-    "code": null,
-    "level": "error",
-    "message": "Please register your known path in the path module",
-    "spans": [
-        {
-            "byte_end": 8285,
-            "byte_start": 8217,
-            "column_end": 77,
-            "column_start": 9,
-            "expansion": {
-                "def_site_span": {
-                    "byte_end": 8294,
-                    "byte_start": 7858,
-                    "column_end": 2,
-                    "column_start": 1,
-                    "expansion": null,
-                    "file_name": "crates/ra_hir_def/src/path.rs",
-                    "is_primary": false,
-                    "label": null,
-                    "line_end": 267,
-                    "line_start": 254,
-                    "suggested_replacement": null,
-                    "suggestion_applicability": null,
-                    "text": [
-                        {
-                            "highlight_end": 28,
-                            "highlight_start": 1,
-                            "text": "macro_rules! __known_path {"
-                        },
-                        {
-                            "highlight_end": 37,
-                            "highlight_start": 1,
-                            "text": "    (std::iter::IntoIterator) => {};"
-                        },
-                        {
-                            "highlight_end": 33,
-                            "highlight_start": 1,
-                            "text": "    (std::result::Result) => {};"
-                        },
-                        {
-                            "highlight_end": 29,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::Range) => {};"
-                        },
-                        {
-                            "highlight_end": 33,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::RangeFrom) => {};"
-                        },
-                        {
-                            "highlight_end": 33,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::RangeFull) => {};"
-                        },
-                        {
-                            "highlight_end": 31,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::RangeTo) => {};"
-                        },
-                        {
-                            "highlight_end": 40,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::RangeToInclusive) => {};"
-                        },
-                        {
-                            "highlight_end": 38,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::RangeInclusive) => {};"
-                        },
-                        {
-                            "highlight_end": 27,
-                            "highlight_start": 1,
-                            "text": "    (std::ops::Try) => {};"
-                        },
-                        {
-                            "highlight_end": 22,
-                            "highlight_start": 1,
-                            "text": "    ($path:path) => {"
-                        },
-                        {
-                            "highlight_end": 77,
-                            "highlight_start": 1,
-                            "text": "        compile_error!(\"Please register your known path in the path module\")"
-                        },
-                        {
-                            "highlight_end": 7,
-                            "highlight_start": 1,
-                            "text": "    };"
-                        },
-                        {
-                            "highlight_end": 2,
-                            "highlight_start": 1,
-                            "text": "}"
-                        }
-                    ]
-                },
-                "macro_decl_name": "$crate::__known_path!",
-                "span": {
-                    "byte_end": 8427,
-                    "byte_start": 8385,
-                    "column_end": 51,
-                    "column_start": 9,
-                    "expansion": {
-                        "def_site_span": {
-                            "byte_end": 8611,
-                            "byte_start": 8312,
-                            "column_end": 2,
-                            "column_start": 1,
-                            "expansion": null,
-                            "file_name": "crates/ra_hir_def/src/path.rs",
-                            "is_primary": false,
-                            "label": null,
-                            "line_end": 277,
-                            "line_start": 270,
-                            "suggested_replacement": null,
-                            "suggestion_applicability": null,
-                            "text": [
-                                {
-                                    "highlight_end": 22,
-                                    "highlight_start": 1,
-                                    "text": "macro_rules! __path {"
-                                },
-                                {
-                                    "highlight_end": 43,
-                                    "highlight_start": 1,
-                                    "text": "    ($start:ident $(:: $seg:ident)*) => ({"
-                                },
-                                {
-                                    "highlight_end": 51,
-                                    "highlight_start": 1,
-                                    "text": "        $crate::__known_path!($start $(:: $seg)*);"
-                                },
-                                {
-                                    "highlight_end": 87,
-                                    "highlight_start": 1,
-                                    "text": "        $crate::path::ModPath::from_simple_segments($crate::path::PathKind::Abs, vec!["
-                                },
-                                {
-                                    "highlight_end": 76,
-                                    "highlight_start": 1,
-                                    "text": "            $crate::path::__name![$start], $($crate::path::__name![$seg],)*"
-                                },
-                                {
-                                    "highlight_end": 11,
-                                    "highlight_start": 1,
-                                    "text": "        ])"
-                                },
-                                {
-                                    "highlight_end": 8,
-                                    "highlight_start": 1,
-                                    "text": "    });"
-                                },
-                                {
-                                    "highlight_end": 2,
-                                    "highlight_start": 1,
-                                    "text": "}"
-                                }
-                            ]
-                        },
-                        "macro_decl_name": "path!",
-                        "span": {
-                            "byte_end": 2966,
-                            "byte_start": 2940,
-                            "column_end": 42,
-                            "column_start": 16,
-                            "expansion": null,
-                            "file_name": "crates/ra_hir_def/src/data.rs",
-                            "is_primary": false,
-                            "label": null,
-                            "line_end": 80,
-                            "line_start": 80,
-                            "suggested_replacement": null,
-                            "suggestion_applicability": null,
-                            "text": [
-                                {
-                                    "highlight_end": 42,
-                                    "highlight_start": 16,
-                                    "text": "    let path = path![std::future::Future];"
-                                }
-                            ]
-                        }
-                    },
-                    "file_name": "crates/ra_hir_def/src/path.rs",
-                    "is_primary": false,
-                    "label": null,
-                    "line_end": 272,
-                    "line_start": 272,
-                    "suggested_replacement": null,
-                    "suggestion_applicability": null,
-                    "text": [
-                        {
-                            "highlight_end": 51,
-                            "highlight_start": 9,
-                            "text": "        $crate::__known_path!($start $(:: $seg)*);"
-                        }
-                    ]
-                }
-            },
-            "file_name": "crates/ra_hir_def/src/path.rs",
-            "is_primary": true,
-            "label": null,
-            "line_end": 265,
-            "line_start": 265,
-            "suggested_replacement": null,
-            "suggestion_applicability": null,
-            "text": [
-                {
-                    "highlight_end": 77,
-                    "highlight_start": 9,
-                    "text": "        compile_error!(\"Please register your known path in the path module\")"
-                }
-            ]
-        }
-    ]
-}
-        "##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
-
-#[test]
-#[cfg(not(windows))]
-fn snap_multi_line_fix() {
-    let diag = parse_diagnostic(
-        r##"{
-            "rendered": "warning: returning the result of a let binding from a block\n --> src/main.rs:4:5\n  |\n3 |     let a = (0..10).collect();\n  |     -------------------------- unnecessary let binding\n4 |     a\n  |     ^\n  |\n  = note: `#[warn(clippy::let_and_return)]` on by default\n  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return\nhelp: return the expression directly\n  |\n3 |     \n4 |     (0..10).collect()\n  |\n\n",
-            "children": [
-                {
-                "children": [],
-                "code": null,
-                "level": "note",
-                "message": "`#[warn(clippy::let_and_return)]` on by default",
-                "rendered": null,
-                "spans": []
-                },
-                {
-                "children": [],
-                "code": null,
-                "level": "help",
-                "message": "for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return",
-                "rendered": null,
-                "spans": []
-                },
-                {
-                "children": [],
-                "code": null,
-                "level": "help",
-                "message": "return the expression directly",
-                "rendered": null,
-                "spans": [
-                    {
-                    "byte_end": 55,
-                    "byte_start": 29,
-                    "column_end": 31,
-                    "column_start": 5,
-                    "expansion": null,
-                    "file_name": "src/main.rs",
-                    "is_primary": true,
-                    "label": null,
-                    "line_end": 3,
-                    "line_start": 3,
-                    "suggested_replacement": "",
-                    "suggestion_applicability": "MachineApplicable",
-                    "text": [
-                        {
-                        "highlight_end": 31,
-                        "highlight_start": 5,
-                        "text": "    let a = (0..10).collect();"
-                        }
-                    ]
-                    },
-                    {
-                    "byte_end": 61,
-                    "byte_start": 60,
-                    "column_end": 6,
-                    "column_start": 5,
-                    "expansion": null,
-                    "file_name": "src/main.rs",
-                    "is_primary": true,
-                    "label": null,
-                    "line_end": 4,
-                    "line_start": 4,
-                    "suggested_replacement": "(0..10).collect()",
-                    "suggestion_applicability": "MachineApplicable",
-                    "text": [
-                        {
-                        "highlight_end": 6,
-                        "highlight_start": 5,
-                        "text": "    a"
-                        }
-                    ]
-                    }
-                ]
-                }
-            ],
-            "code": {
-                "code": "clippy::let_and_return",
-                "explanation": null
-            },
-            "level": "warning",
-            "message": "returning the result of a let binding from a block",
-            "spans": [
-                {
-                "byte_end": 55,
-                "byte_start": 29,
-                "column_end": 31,
-                "column_start": 5,
-                "expansion": null,
-                "file_name": "src/main.rs",
-                "is_primary": false,
-                "label": "unnecessary let binding",
-                "line_end": 3,
-                "line_start": 3,
-                "suggested_replacement": null,
-                "suggestion_applicability": null,
-                "text": [
-                    {
-                    "highlight_end": 31,
-                    "highlight_start": 5,
-                    "text": "    let a = (0..10).collect();"
-                    }
-                ]
-                },
-                {
-                "byte_end": 61,
-                "byte_start": 60,
-                "column_end": 6,
-                "column_start": 5,
-                "expansion": null,
-                "file_name": "src/main.rs",
-                "is_primary": true,
-                "label": null,
-                "line_end": 4,
-                "line_start": 4,
-                "suggested_replacement": null,
-                "suggestion_applicability": null,
-                "text": [
-                    {
-                    "highlight_end": 6,
-                    "highlight_start": 5,
-                    "text": "    a"
-                    }
-                ]
-                }
-            ]
-        }
-        "##,
-    );
-
-    let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
-    insta::assert_debug_snapshot!(diag);
-}
diff --git a/crates/ra_flycheck/src/lib.rs b/crates/ra_flycheck/src/lib.rs
index d5efb6ab3..041e38a9f 100644
--- a/crates/ra_flycheck/src/lib.rs
+++ b/crates/ra_flycheck/src/lib.rs
@@ -1,10 +1,9 @@
 //! cargo_check provides the functionality needed to run `cargo check` or
 //! another compatible command (f.x. clippy) in a background thread and provide
 //! LSP diagnostics based on the output of the command.
-mod conv;
 
 use std::{
-    io::{self, BufRead, BufReader},
+    io::{self, BufReader},
     path::PathBuf,
     process::{Command, Stdio},
     time::Instant,
@@ -12,14 +11,10 @@ use std::{
 
 use cargo_metadata::Message;
 use crossbeam_channel::{never, select, unbounded, Receiver, RecvError, Sender};
-use lsp_types::{
-    CodeAction, CodeActionOrCommand, Diagnostic, Url, WorkDoneProgress, WorkDoneProgressBegin,
-    WorkDoneProgressEnd, WorkDoneProgressReport,
-};
-
-use crate::conv::{map_rust_diagnostic_to_lsp, MappedRustDiagnostic};
 
-pub use crate::conv::url_from_path_with_drive_lowercasing;
+pub use cargo_metadata::diagnostic::{
+    Applicability, Diagnostic, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion,
+};
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum FlycheckConfig {
@@ -61,10 +56,17 @@ pub enum CheckTask {
     ClearDiagnostics,
 
     /// Request adding a diagnostic with fixes included to a file
-    AddDiagnostic { url: Url, diagnostic: Diagnostic, fixes: Vec<CodeActionOrCommand> },
+    AddDiagnostic { workspace_root: PathBuf, diagnostic: Diagnostic },
 
     /// Request check progress notification to client
-    Status(WorkDoneProgress),
+    Status(Status),
+}
+
+#[derive(Debug)]
+pub enum Status {
+    Being,
+    Progress(String),
+    End,
 }
 
 pub enum CheckCommand {
@@ -131,9 +133,7 @@ impl FlycheckThread {
 
     fn clean_previous_results(&self, task_send: &Sender<CheckTask>) {
         task_send.send(CheckTask::ClearDiagnostics).unwrap();
-        task_send
-            .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd { message: None })))
-            .unwrap();
+        task_send.send(CheckTask::Status(Status::End)).unwrap();
     }
 
     fn should_recheck(&mut self) -> bool {
@@ -155,52 +155,24 @@ impl FlycheckThread {
     fn handle_message(&self, msg: CheckEvent, task_send: &Sender<CheckTask>) {
         match msg {
             CheckEvent::Begin => {
-                task_send
-                    .send(CheckTask::Status(WorkDoneProgress::Begin(WorkDoneProgressBegin {
-                        title: "Running `cargo check`".to_string(),
-                        cancellable: Some(false),
-                        message: None,
-                        percentage: None,
-                    })))
-                    .unwrap();
+                task_send.send(CheckTask::Status(Status::Being)).unwrap();
             }
 
             CheckEvent::End => {
-                task_send
-                    .send(CheckTask::Status(WorkDoneProgress::End(WorkDoneProgressEnd {
-                        message: None,
-                    })))
-                    .unwrap();
+                task_send.send(CheckTask::Status(Status::End)).unwrap();
             }
 
             CheckEvent::Msg(Message::CompilerArtifact(msg)) => {
-                task_send
-                    .send(CheckTask::Status(WorkDoneProgress::Report(WorkDoneProgressReport {
-                        cancellable: Some(false),
-                        message: Some(msg.target.name),
-                        percentage: None,
-                    })))
-                    .unwrap();
+                task_send.send(CheckTask::Status(Status::Progress(msg.target.name))).unwrap();
             }
 
             CheckEvent::Msg(Message::CompilerMessage(msg)) => {
-                let map_result = map_rust_diagnostic_to_lsp(&msg.message, &self.workspace_root);
-                if map_result.is_empty() {
-                    return;
-                }
-
-                for MappedRustDiagnostic { location, diagnostic, fixes } in map_result {
-                    let fixes = fixes
-                        .into_iter()
-                        .map(|fix| {
-                            CodeAction { diagnostics: Some(vec![diagnostic.clone()]), ..fix }.into()
-                        })
-                        .collect();
-
-                    task_send
-                        .send(CheckTask::AddDiagnostic { url: location.uri, diagnostic, fixes })
-                        .unwrap();
-                }
+                task_send
+                    .send(CheckTask::AddDiagnostic {
+                        workspace_root: self.workspace_root.clone(),
+                        diagnostic: msg.message,
+                    })
+                    .unwrap();
             }
 
             CheckEvent::Msg(Message::BuildScriptExecuted(_msg)) => {}
@@ -271,12 +243,6 @@ impl FlycheckThread {
     }
 }
 
-#[derive(Debug)]
-pub struct DiagnosticWithFixes {
-    diagnostic: Diagnostic,
-    fixes: Vec<CodeAction>,
-}
-
 enum CheckEvent {
     Begin,
     Msg(cargo_metadata::Message),
@@ -300,15 +266,11 @@ fn run_cargo(
     // erroneus output.
     let stdout = BufReader::new(child.stdout.take().unwrap());
     let mut read_at_least_one_message = false;
-
-    for line in stdout.lines() {
-        let line = line?;
-
-        let message = serde_json::from_str::<cargo_metadata::Message>(&line);
+    for message in cargo_metadata::Message::parse_stream(stdout) {
         let message = match message {
             Ok(message) => message,
             Err(err) => {
-                log::error!("Invalid json from cargo check, ignoring ({}): {:?} ", err, line);
+                log::error!("Invalid json from cargo check, ignoring ({})", err);
                 continue;
             }
         };
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index e8e3211fc..840cfdfc8 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -989,6 +989,17 @@ impl TypeParam {
             ty: InEnvironment { value: ty, environment },
         }
     }
+
+    pub fn default(self, db: &dyn HirDatabase) -> Option<Type> {
+        let params = db.generic_defaults(self.id.parent);
+        let local_idx = hir_ty::param_idx(db, self.id)?;
+        let resolver = self.id.parent.resolver(db.upcast());
+        let environment = TraitEnvironment::lower(db, &resolver);
+        params.get(local_idx).cloned().map(|ty| Type {
+            krate: self.id.parent.module(db.upcast()).krate,
+            ty: InEnvironment { value: ty, environment },
+        })
+    }
 }
 
 // FIXME: rename from `ImplDef` to `Impl`
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index e8f3482fe..ccc4348f4 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -427,6 +427,11 @@ impl Substs {
     }
 }
 
+/// Return an index of a parameter in the generic type parameter list by it's id.
+pub fn param_idx(db: &dyn HirDatabase, id: TypeParamId) -> Option<usize> {
+    generics(db.upcast(), id.parent).param_idx(id)
+}
+
 #[derive(Debug, Clone)]
 pub struct SubstsBuilder {
     vec: Vec<Ty>,
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index b6b9627de..da336973c 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -34,7 +34,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) record_pat_syntax: Option<ast::RecordPat>,
     pub(super) record_field_syntax: Option<ast::RecordField>,
     pub(super) impl_def: Option<ast::ImplDef>,
-    /// FIXME: `ActiveParameter` is string-based, which is very wrong
+    /// FIXME: `ActiveParameter` is string-based, which is very very wrong
     pub(super) active_parameter: Option<ActiveParameter>,
     pub(super) is_param: bool,
     /// If a name-binding or reference to a const in a pattern.
diff --git a/crates/ra_ide/src/completion/presentation.rs b/crates/ra_ide/src/completion/presentation.rs
index 2edb130cf..077cf9647 100644
--- a/crates/ra_ide/src/completion/presentation.rs
+++ b/crates/ra_ide/src/completion/presentation.rs
@@ -17,12 +17,11 @@ use crate::{
 impl Completions {
     pub(crate) fn add_field(&mut self, ctx: &CompletionContext, field: hir::Field, ty: &Type) {
         let is_deprecated = is_deprecated(field, ctx.db);
-        let ty = ty.display(ctx.db).to_string();
         let name = field.name(ctx.db);
         let mut completion_item =
             CompletionItem::new(CompletionKind::Reference, ctx.source_range(), name.to_string())
                 .kind(CompletionItemKind::Field)
-                .detail(ty.clone())
+                .detail(ty.display(ctx.db).to_string())
                 .set_documentation(field.docs(ctx.db))
                 .set_deprecated(is_deprecated);
 
@@ -107,6 +106,12 @@ impl Completions {
             }
         };
 
+        if let ScopeDef::Local(local) = resolution {
+            if let Some(score) = compute_score(ctx, &local.ty(ctx.db), &local_name) {
+                completion_item = completion_item.set_score(score);
+            }
+        }
+
         // Add `<>` for generic types
         if ctx.is_path_type && !ctx.has_type_args && ctx.config.add_call_parenthesis {
             if let Some(cap) = ctx.config.snippet_cap {
@@ -319,10 +324,11 @@ impl Completions {
 
 pub(crate) fn compute_score(
     ctx: &CompletionContext,
-    // FIXME: this definitely should be a `Type`
-    ty: &str,
+    ty: &Type,
     name: &str,
 ) -> Option<CompletionScore> {
+    // FIXME: this should not fall back to string equality.
+    let ty = &ty.display(ctx.db).to_string();
     let (active_name, active_type) = if let Some(record_field) = &ctx.record_field_syntax {
         tested_by!(test_struct_field_completion_in_record_lit);
         let (struct_field, _local) = ctx.sema.resolve_record_field(record_field)?;
@@ -1405,4 +1411,48 @@ mod tests {
         "###
         );
     }
+
+    #[test]
+    fn prioritize_exact_ref_match() {
+        assert_debug_snapshot!(
+        do_reference_completion(
+                r"
+                    struct WorldSnapshot { _f: () };
+                    fn go(world: &WorldSnapshot) {
+                        go(w<|>)
+                    }
+                    ",
+        ),
+            @r###"
+        [
+            CompletionItem {
+                label: "WorldSnapshot",
+                source_range: 132..133,
+                delete: 132..133,
+                insert: "WorldSnapshot",
+                kind: Struct,
+            },
+            CompletionItem {
+                label: "go(…)",
+                source_range: 132..133,
+                delete: 132..133,
+                insert: "go(${1:world})$0",
+                kind: Function,
+                lookup: "go",
+                detail: "fn go(world: &WorldSnapshot)",
+                trigger_call_info: true,
+            },
+            CompletionItem {
+                label: "world",
+                source_range: 132..133,
+                delete: 132..133,
+                insert: "world",
+                kind: Binding,
+                detail: "&WorldSnapshot",
+                score: TypeAndNameMatch,
+            },
+        ]
+        "###
+        );
+    }
 }
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 915199bd8..78149ddfc 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -176,14 +176,10 @@ impl AnalysisHost {
     pub fn request_cancellation(&mut self) {
         self.db.request_cancellation();
     }
-    pub fn raw_database(
-        &self,
-    ) -> &(impl hir::db::HirDatabase + salsa::Database + ra_db::SourceDatabaseExt) {
+    pub fn raw_database(&self) -> &RootDatabase {
         &self.db
     }
-    pub fn raw_database_mut(
-        &mut self,
-    ) -> &mut (impl hir::db::HirDatabase + salsa::Database + ra_db::SourceDatabaseExt) {
+    pub fn raw_database_mut(&mut self) -> &mut RootDatabase {
         &mut self.db
     }
 }
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index 4f098b706..a2e9f65ef 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -35,7 +35,7 @@ pub enum ProjectWorkspace {
 /// `PackageRoot` describes a package root folder.
 /// Which may be an external dependency, or a member of
 /// the current workspace.
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct PackageRoot {
     /// Path to the root folder
     path: PathBuf,
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index 12c5228f5..d0e960fb4 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -13,6 +13,10 @@ pub fn name_ref(text: &str) -> ast::NameRef {
     ast_from_text(&format!("fn f() {{ {}; }}", text))
 }
 
+pub fn type_ref(text: &str) -> ast::TypeRef {
+    ast_from_text(&format!("impl {} for D {{}};", text))
+}
+
 pub fn path_segment(name_ref: ast::NameRef) -> ast::PathSegment {
     ast_from_text(&format!("use {};", name_ref))
 }
diff --git a/crates/ra_text_edit/src/lib.rs b/crates/ra_text_edit/src/lib.rs
index 37f77cc47..c4f945101 100644
--- a/crates/ra_text_edit/src/lib.rs
+++ b/crates/ra_text_edit/src/lib.rs
@@ -21,7 +21,7 @@ pub struct TextEdit {
     indels: Vec<Indel>,
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug, Default, Clone)]
 pub struct TextEditBuilder {
     indels: Vec<Indel>,
 }
diff --git a/crates/rust-analyzer/Cargo.toml b/crates/rust-analyzer/Cargo.toml
index 8c94f430a..9b2d29b1d 100644
--- a/crates/rust-analyzer/Cargo.toml
+++ b/crates/rust-analyzer/Cargo.toml
@@ -53,6 +53,7 @@ winapi = "0.3.8"
 
 [dev-dependencies]
 tempfile = "3.1.0"
+insta = "0.16.0"
 test_utils = { path = "../test_utils" }
 
 [features]
diff --git a/crates/rust-analyzer/src/cli.rs b/crates/rust-analyzer/src/cli.rs
index a865a7c7e..39ce77900 100644
--- a/crates/rust-analyzer/src/cli.rs
+++ b/crates/rust-analyzer/src/cli.rs
@@ -16,6 +16,7 @@ use ra_syntax::{AstNode, SourceFile};
 pub use analysis_bench::{analysis_bench, BenchWhat, Position};
 pub use analysis_stats::analysis_stats;
 pub use diagnostics::diagnostics;
+pub use load_cargo::load_cargo;
 
 #[derive(Clone, Copy)]
 pub enum Verbosity {
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index 023ced6cf..8eaf75ff6 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -22,7 +22,7 @@ fn vfs_root_to_id(r: ra_vfs::VfsRoot) -> SourceRootId {
     SourceRootId(r.0)
 }
 
-pub(crate) fn load_cargo(
+pub fn load_cargo(
     root: &Path,
     load_out_dirs_from_check: bool,
     with_proc_macro: bool,
diff --git a/crates/rust-analyzer/src/diagnostics.rs b/crates/rust-analyzer/src/diagnostics.rs
index e7924f0a3..4bdd45a7d 100644
--- a/crates/rust-analyzer/src/diagnostics.rs
+++ b/crates/rust-analyzer/src/diagnostics.rs
@@ -1,4 +1,5 @@
 //! Book keeping for keeping diagnostics easily in sync with the client.
+pub(crate) mod to_proto;
 
 use std::{collections::HashMap, sync::Arc};
 
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_clippy_pass_by_ref.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_clippy_pass_by_ref.snap
index 4c9db0385..d7f9ec049 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_clippy_pass_by_ref.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_clippy_pass_by_ref.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_handles_macro_location.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_handles_macro_location.snap
index 7cde4d867..a59faf254 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_handles_macro_location.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_handles_macro_location.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_macro_compiler_error.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_macro_compiler_error.snap
index 1cc37e087..3c78e7f36 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_macro_compiler_error.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_macro_compiler_error.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_multi_line_fix.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
index 615ed8378..076b3cf27 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_multi_line_fix.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_incompatible_type_for_trait.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_incompatible_type_for_trait.snap
index 0df0fce18..46d0c56d2 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_incompatible_type_for_trait.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_incompatible_type_for_trait.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_mismatched_type.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_mismatched_type.snap
index 28ebcb3b3..4182929ba 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_mismatched_type.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_mismatched_type.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_unused_variable.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
index 5e0873281..69138c15b 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_unused_variable.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_wrong_number_of_parameters.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_wrong_number_of_parameters.snap
index e500d3cd6..f6ab05004 100644
--- a/crates/ra_flycheck/src/conv/snapshots/ra_flycheck__conv__test__snap_rustc_wrong_number_of_parameters.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_wrong_number_of_parameters.snap
@@ -1,5 +1,5 @@
 ---
-source: crates/ra_flycheck/src/conv/test.rs
+source: crates/rust-analyzer/src/diagnostics/to_proto.rs
 expression: diag
 ---
 [
diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
new file mode 100644
index 000000000..eabf4908f
--- /dev/null
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -0,0 +1,1397 @@
+//! This module provides the functionality needed to convert diagnostics from
+//! `cargo check` json format to the LSP diagnostic format.
+use std::{
+    collections::HashMap,
+    path::{Component, Path, Prefix},
+    str::FromStr,
+};
+
+use lsp_types::{
+    CodeAction, Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag,
+    Location, NumberOrString, Position, Range, TextEdit, Url, WorkspaceEdit,
+};
+use ra_flycheck::{Applicability, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion};
+use stdx::format_to;
+
+use crate::Result;
+
+/// Converts a Rust level string to a LSP severity
+fn map_level_to_severity(val: DiagnosticLevel) -> Option<DiagnosticSeverity> {
+    let res = match val {
+        DiagnosticLevel::Ice => DiagnosticSeverity::Error,
+        DiagnosticLevel::Error => DiagnosticSeverity::Error,
+        DiagnosticLevel::Warning => DiagnosticSeverity::Warning,
+        DiagnosticLevel::Note => DiagnosticSeverity::Information,
+        DiagnosticLevel::Help => DiagnosticSeverity::Hint,
+        DiagnosticLevel::Unknown => return None,
+    };
+    Some(res)
+}
+
+/// Check whether a file name is from macro invocation
+fn is_from_macro(file_name: &str) -> bool {
+    file_name.starts_with('<') && file_name.ends_with('>')
+}
+
+/// Converts a Rust macro span to a LSP location recursively
+fn map_macro_span_to_location(
+    span_macro: &DiagnosticSpanMacroExpansion,
+    workspace_root: &Path,
+) -> Option<Location> {
+    if !is_from_macro(&span_macro.span.file_name) {
+        return Some(map_span_to_location(&span_macro.span, workspace_root));
+    }
+
+    if let Some(expansion) = &span_macro.span.expansion {
+        return map_macro_span_to_location(&expansion, workspace_root);
+    }
+
+    None
+}
+
+/// Converts a Rust span to a LSP location, resolving macro expansion site if neccesary
+fn map_span_to_location(span: &DiagnosticSpan, workspace_root: &Path) -> Location {
+    if span.expansion.is_some() {
+        let expansion = span.expansion.as_ref().unwrap();
+        if let Some(macro_range) = map_macro_span_to_location(&expansion, workspace_root) {
+            return macro_range;
+        }
+    }
+
+    map_span_to_location_naive(span, workspace_root)
+}
+
+/// Converts a Rust span to a LSP location
+fn map_span_to_location_naive(span: &DiagnosticSpan, workspace_root: &Path) -> Location {
+    let mut file_name = workspace_root.to_path_buf();
+    file_name.push(&span.file_name);
+    let uri = url_from_path_with_drive_lowercasing(file_name).unwrap();
+
+    // FIXME: this doesn't handle UTF16 offsets correctly
+    let range = Range::new(
+        Position::new(span.line_start as u64 - 1, span.column_start as u64 - 1),
+        Position::new(span.line_end as u64 - 1, span.column_end as u64 - 1),
+    );
+
+    Location { uri, range }
+}
+
+/// Converts a secondary Rust span to a LSP related information
+///
+/// If the span is unlabelled this will return `None`.
+fn map_secondary_span_to_related(
+    span: &DiagnosticSpan,
+    workspace_root: &Path,
+) -> Option<DiagnosticRelatedInformation> {
+    let message = span.label.clone()?;
+    let location = map_span_to_location(span, workspace_root);
+    Some(DiagnosticRelatedInformation { location, message })
+}
+
+/// Determines if diagnostic is related to unused code
+fn is_unused_or_unnecessary(rd: &ra_flycheck::Diagnostic) -> bool {
+    match &rd.code {
+        Some(code) => match code.code.as_str() {
+            "dead_code" | "unknown_lints" | "unreachable_code" | "unused_attributes"
+            | "unused_imports" | "unused_macros" | "unused_variables" => true,
+            _ => false,
+        },
+        None => false,
+    }
+}
+
+/// Determines if diagnostic is related to deprecated code
+fn is_deprecated(rd: &ra_flycheck::Diagnostic) -> bool {
+    match &rd.code {
+        Some(code) => code.code.as_str() == "deprecated",
+        None => false,
+    }
+}
+
+enum MappedRustChildDiagnostic {
+    Related(DiagnosticRelatedInformation),
+    SuggestedFix(CodeAction),
+    MessageLine(String),
+}
+
+fn map_rust_child_diagnostic(
+    rd: &ra_flycheck::Diagnostic,
+    workspace_root: &Path,
+) -> MappedRustChildDiagnostic {
+    let spans: Vec<&DiagnosticSpan> = rd.spans.iter().filter(|s| s.is_primary).collect();
+    if spans.is_empty() {
+        // `rustc` uses these spanless children as a way to print multi-line
+        // messages
+        return MappedRustChildDiagnostic::MessageLine(rd.message.clone());
+    }
+
+    let mut edit_map: HashMap<Url, Vec<TextEdit>> = HashMap::new();
+    for &span in &spans {
+        match (&span.suggestion_applicability, &span.suggested_replacement) {
+            (Some(Applicability::MachineApplicable), Some(suggested_replacement)) => {
+                let location = map_span_to_location(span, workspace_root);
+                let edit = TextEdit::new(location.range, suggested_replacement.clone());
+                edit_map.entry(location.uri).or_default().push(edit);
+            }
+            _ => {}
+        }
+    }
+
+    if edit_map.is_empty() {
+        MappedRustChildDiagnostic::Related(DiagnosticRelatedInformation {
+            location: map_span_to_location(spans[0], workspace_root),
+            message: rd.message.clone(),
+        })
+    } else {
+        MappedRustChildDiagnostic::SuggestedFix(CodeAction {
+            title: rd.message.clone(),
+            kind: Some("quickfix".to_string()),
+            diagnostics: None,
+            edit: Some(WorkspaceEdit::new(edit_map)),
+            command: None,
+            is_preferred: None,
+        })
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct MappedRustDiagnostic {
+    pub location: Location,
+    pub diagnostic: Diagnostic,
+    pub fixes: Vec<CodeAction>,
+}
+
+/// Converts a Rust root diagnostic to LSP form
+///
+/// This flattens the Rust diagnostic by:
+///
+/// 1. Creating a LSP diagnostic with the root message and primary span.
+/// 2. Adding any labelled secondary spans to `relatedInformation`
+/// 3. Categorising child diagnostics as either `SuggestedFix`es,
+///    `relatedInformation` or additional message lines.
+///
+/// If the diagnostic has no primary span this will return `None`
+pub(crate) fn map_rust_diagnostic_to_lsp(
+    rd: &ra_flycheck::Diagnostic,
+    workspace_root: &Path,
+) -> Vec<MappedRustDiagnostic> {
+    let primary_spans: Vec<&DiagnosticSpan> = rd.spans.iter().filter(|s| s.is_primary).collect();
+    if primary_spans.is_empty() {
+        return Vec::new();
+    }
+
+    let severity = map_level_to_severity(rd.level);
+
+    let mut source = String::from("rustc");
+    let mut code = rd.code.as_ref().map(|c| c.code.clone());
+    if let Some(code_val) = &code {
+        // See if this is an RFC #2103 scoped lint (e.g. from Clippy)
+        let scoped_code: Vec<&str> = code_val.split("::").collect();
+        if scoped_code.len() == 2 {
+            source = String::from(scoped_code[0]);
+            code = Some(String::from(scoped_code[1]));
+        }
+    }
+
+    let mut needs_primary_span_label = true;
+    let mut related_information = Vec::new();
+    let mut tags = Vec::new();
+
+    for secondary_span in rd.spans.iter().filter(|s| !s.is_primary) {
+        let related = map_secondary_span_to_related(secondary_span, workspace_root);
+        if let Some(related) = related {
+            related_information.push(related);
+        }
+    }
+
+    let mut fixes = Vec::new();
+    let mut message = rd.message.clone();
+    for child in &rd.children {
+        let child = map_rust_child_diagnostic(&child, workspace_root);
+        match child {
+            MappedRustChildDiagnostic::Related(related) => related_information.push(related),
+            MappedRustChildDiagnostic::SuggestedFix(code_action) => fixes.push(code_action),
+            MappedRustChildDiagnostic::MessageLine(message_line) => {
+                format_to!(message, "\n{}", message_line);
+
+                // These secondary messages usually duplicate the content of the
+                // primary span label.
+                needs_primary_span_label = false;
+            }
+        }
+    }
+
+    if is_unused_or_unnecessary(rd) {
+        tags.push(DiagnosticTag::Unnecessary);
+    }
+
+    if is_deprecated(rd) {
+        tags.push(DiagnosticTag::Deprecated);
+    }
+
+    primary_spans
+        .iter()
+        .map(|primary_span| {
+            let location = map_span_to_location(&primary_span, workspace_root);
+
+            let mut message = message.clone();
+            if needs_primary_span_label {
+                if let Some(primary_span_label) = &primary_span.label {
+                    format_to!(message, "\n{}", primary_span_label);
+                }
+            }
+
+            // If error occurs from macro expansion, add related info pointing to
+            // where the error originated
+            if !is_from_macro(&primary_span.file_name) && primary_span.expansion.is_some() {
+                let def_loc = map_span_to_location_naive(&primary_span, workspace_root);
+                related_information.push(DiagnosticRelatedInformation {
+                    location: def_loc,
+                    message: "Error originated from macro here".to_string(),
+                });
+            }
+
+            let diagnostic = Diagnostic {
+                range: location.range,
+                severity,
+                code: code.clone().map(NumberOrString::String),
+                source: Some(source.clone()),
+                message,
+                related_information: if related_information.is_empty() {
+                    None
+                } else {
+                    Some(related_information.clone())
+                },
+                tags: if tags.is_empty() { None } else { Some(tags.clone()) },
+            };
+
+            MappedRustDiagnostic { location, diagnostic, fixes: fixes.clone() }
+        })
+        .collect()
+}
+
+/// Returns a `Url` object from a given path, will lowercase drive letters if present.
+/// This will only happen when processing windows paths.
+///
+/// When processing non-windows path, this is essentially the same as `Url::from_file_path`.
+pub fn url_from_path_with_drive_lowercasing(path: impl AsRef<Path>) -> Result<Url> {
+    let component_has_windows_drive = path.as_ref().components().any(|comp| {
+        if let Component::Prefix(c) = comp {
+            return matches!(c.kind(), Prefix::Disk(_) | Prefix::VerbatimDisk(_));
+        }
+        false
+    });
+
+    // VSCode expects drive letters to be lowercased, where rust will uppercase the drive letters.
+    let res = if component_has_windows_drive {
+        let url_original = Url::from_file_path(&path)
+            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?;
+
+        let drive_partition: Vec<&str> = url_original.as_str().rsplitn(2, ':').collect();
+
+        // There is a drive partition, but we never found a colon.
+        // This should not happen, but in this case we just pass it through.
+        if drive_partition.len() == 1 {
+            return Ok(url_original);
+        }
+
+        let joined = drive_partition[1].to_ascii_lowercase() + ":" + drive_partition[0];
+        let url = Url::from_str(&joined).expect("This came from a valid `Url`");
+
+        url
+    } else {
+        Url::from_file_path(&path)
+            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?
+    };
+    Ok(res)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // `Url` is not able to parse windows paths on unix machines.
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn test_lowercase_drive_letter_with_drive() {
+        let url = url_from_path_with_drive_lowercasing("C:\\Test").unwrap();
+
+        assert_eq!(url.to_string(), "file:///c:/Test");
+    }
+
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn test_drive_without_colon_passthrough() {
+        let url = url_from_path_with_drive_lowercasing(r#"\\localhost\C$\my_dir"#).unwrap();
+
+        assert_eq!(url.to_string(), "file://localhost/C$/my_dir");
+    }
+
+    #[cfg(not(windows))]
+    fn parse_diagnostic(val: &str) -> ra_flycheck::Diagnostic {
+        serde_json::from_str::<ra_flycheck::Diagnostic>(val).unwrap()
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_rustc_incompatible_type_for_trait() {
+        let diag = parse_diagnostic(
+            r##"{
+                "message": "method `next` has an incompatible type for trait",
+                "code": {
+                    "code": "E0053",
+                    "explanation": "\nThe parameters of any trait method must match between a trait implementation\nand the trait definition.\n\nHere are a couple examples of this error:\n\n```compile_fail,E0053\ntrait Foo {\n    fn foo(x: u16);\n    fn bar(&self);\n}\n\nstruct Bar;\n\nimpl Foo for Bar {\n    // error, expected u16, found i16\n    fn foo(x: i16) { }\n\n    // error, types differ in mutability\n    fn bar(&mut self) { }\n}\n```\n"
+                },
+                "level": "error",
+                "spans": [
+                    {
+                        "file_name": "compiler/ty/list_iter.rs",
+                        "byte_start": 1307,
+                        "byte_end": 1350,
+                        "line_start": 52,
+                        "line_end": 52,
+                        "column_start": 5,
+                        "column_end": 48,
+                        "is_primary": true,
+                        "text": [
+                            {
+                                "text": "    fn next(&self) -> Option<&'list ty::Ref<M>> {",
+                                "highlight_start": 5,
+                                "highlight_end": 48
+                            }
+                        ],
+                        "label": "types differ in mutability",
+                        "suggested_replacement": null,
+                        "suggestion_applicability": null,
+                        "expansion": null
+                    }
+                ],
+                "children": [
+                    {
+                        "message": "expected type `fn(&mut ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&ty::Ref<M>>`\n   found type `fn(&ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&'list ty::Ref<M>>`",
+                        "code": null,
+                        "level": "note",
+                        "spans": [],
+                        "children": [],
+                        "rendered": null
+                    }
+                ],
+                "rendered": "error[E0053]: method `next` has an incompatible type for trait\n  --> compiler/ty/list_iter.rs:52:5\n   |\n52 |     fn next(&self) -> Option<&'list ty::Ref<M>> {\n   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ types differ in mutability\n   |\n   = note: expected type `fn(&mut ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&ty::Ref<M>>`\n              found type `fn(&ty::list_iter::ListIterator<'list, M>) -> std::option::Option<&'list ty::Ref<M>>`\n\n"
+            }
+            "##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_rustc_unused_variable() {
+        let diag = parse_diagnostic(
+            r##"{
+    "message": "unused variable: `foo`",
+    "code": {
+        "code": "unused_variables",
+        "explanation": null
+    },
+    "level": "warning",
+    "spans": [
+        {
+            "file_name": "driver/subcommand/repl.rs",
+            "byte_start": 9228,
+            "byte_end": 9231,
+            "line_start": 291,
+            "line_end": 291,
+            "column_start": 9,
+            "column_end": 12,
+            "is_primary": true,
+            "text": [
+                {
+                    "text": "    let foo = 42;",
+                    "highlight_start": 9,
+                    "highlight_end": 12
+                }
+            ],
+            "label": null,
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        }
+    ],
+    "children": [
+        {
+            "message": "#[warn(unused_variables)] on by default",
+            "code": null,
+            "level": "note",
+            "spans": [],
+            "children": [],
+            "rendered": null
+        },
+        {
+            "message": "consider prefixing with an underscore",
+            "code": null,
+            "level": "help",
+            "spans": [
+                {
+                    "file_name": "driver/subcommand/repl.rs",
+                    "byte_start": 9228,
+                    "byte_end": 9231,
+                    "line_start": 291,
+                    "line_end": 291,
+                    "column_start": 9,
+                    "column_end": 12,
+                    "is_primary": true,
+                    "text": [
+                        {
+                            "text": "    let foo = 42;",
+                            "highlight_start": 9,
+                            "highlight_end": 12
+                        }
+                    ],
+                    "label": null,
+                    "suggested_replacement": "_foo",
+                    "suggestion_applicability": "MachineApplicable",
+                    "expansion": null
+                }
+            ],
+            "children": [],
+            "rendered": null
+        }
+    ],
+    "rendered": "warning: unused variable: `foo`\n   --> driver/subcommand/repl.rs:291:9\n    |\n291 |     let foo = 42;\n    |         ^^^ help: consider prefixing with an underscore: `_foo`\n    |\n    = note: #[warn(unused_variables)] on by default\n\n"
+    }"##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_rustc_wrong_number_of_parameters() {
+        let diag = parse_diagnostic(
+            r##"{
+    "message": "this function takes 2 parameters but 3 parameters were supplied",
+    "code": {
+        "code": "E0061",
+        "explanation": "\nThe number of arguments passed to a function must match the number of arguments\nspecified in the function signature.\n\nFor example, a function like:\n\n```\nfn f(a: u16, b: &str) {}\n```\n\nMust always be called with exactly two arguments, e.g., `f(2, \"test\")`.\n\nNote that Rust does not have a notion of optional function arguments or\nvariadic functions (except for its C-FFI).\n"
+    },
+    "level": "error",
+    "spans": [
+        {
+            "file_name": "compiler/ty/select.rs",
+            "byte_start": 8787,
+            "byte_end": 9241,
+            "line_start": 219,
+            "line_end": 231,
+            "column_start": 5,
+            "column_end": 6,
+            "is_primary": false,
+            "text": [
+                {
+                    "text": "    pub fn add_evidence(",
+                    "highlight_start": 5,
+                    "highlight_end": 25
+                },
+                {
+                    "text": "        &mut self,",
+                    "highlight_start": 1,
+                    "highlight_end": 19
+                },
+                {
+                    "text": "        target_poly: &ty::Ref<ty::Poly>,",
+                    "highlight_start": 1,
+                    "highlight_end": 41
+                },
+                {
+                    "text": "        evidence_poly: &ty::Ref<ty::Poly>,",
+                    "highlight_start": 1,
+                    "highlight_end": 43
+                },
+                {
+                    "text": "    ) {",
+                    "highlight_start": 1,
+                    "highlight_end": 8
+                },
+                {
+                    "text": "        match target_poly {",
+                    "highlight_start": 1,
+                    "highlight_end": 28
+                },
+                {
+                    "text": "            ty::Ref::Var(tvar, _) => self.add_var_evidence(tvar, evidence_poly),",
+                    "highlight_start": 1,
+                    "highlight_end": 81
+                },
+                {
+                    "text": "            ty::Ref::Fixed(target_ty) => {",
+                    "highlight_start": 1,
+                    "highlight_end": 43
+                },
+                {
+                    "text": "                let evidence_ty = evidence_poly.resolve_to_ty();",
+                    "highlight_start": 1,
+                    "highlight_end": 65
+                },
+                {
+                    "text": "                self.add_evidence_ty(target_ty, evidence_poly, evidence_ty)",
+                    "highlight_start": 1,
+                    "highlight_end": 76
+                },
+                {
+                    "text": "            }",
+                    "highlight_start": 1,
+                    "highlight_end": 14
+                },
+                {
+                    "text": "        }",
+                    "highlight_start": 1,
+                    "highlight_end": 10
+                },
+                {
+                    "text": "    }",
+                    "highlight_start": 1,
+                    "highlight_end": 6
+                }
+            ],
+            "label": "defined here",
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        },
+        {
+            "file_name": "compiler/ty/select.rs",
+            "byte_start": 4045,
+            "byte_end": 4057,
+            "line_start": 104,
+            "line_end": 104,
+            "column_start": 18,
+            "column_end": 30,
+            "is_primary": true,
+            "text": [
+                {
+                    "text": "            self.add_evidence(target_fixed, evidence_fixed, false);",
+                    "highlight_start": 18,
+                    "highlight_end": 30
+                }
+            ],
+            "label": "expected 2 parameters",
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        }
+    ],
+    "children": [],
+    "rendered": "error[E0061]: this function takes 2 parameters but 3 parameters were supplied\n   --> compiler/ty/select.rs:104:18\n    |\n104 |               self.add_evidence(target_fixed, evidence_fixed, false);\n    |                    ^^^^^^^^^^^^ expected 2 parameters\n...\n219 | /     pub fn add_evidence(\n220 | |         &mut self,\n221 | |         target_poly: &ty::Ref<ty::Poly>,\n222 | |         evidence_poly: &ty::Ref<ty::Poly>,\n...   |\n230 | |         }\n231 | |     }\n    | |_____- defined here\n\n"
+    }"##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_clippy_pass_by_ref() {
+        let diag = parse_diagnostic(
+            r##"{
+    "message": "this argument is passed by reference, but would be more efficient if passed by value",
+    "code": {
+        "code": "clippy::trivially_copy_pass_by_ref",
+        "explanation": null
+    },
+    "level": "warning",
+    "spans": [
+        {
+            "file_name": "compiler/mir/tagset.rs",
+            "byte_start": 941,
+            "byte_end": 946,
+            "line_start": 42,
+            "line_end": 42,
+            "column_start": 24,
+            "column_end": 29,
+            "is_primary": true,
+            "text": [
+                {
+                    "text": "    pub fn is_disjoint(&self, other: Self) -> bool {",
+                    "highlight_start": 24,
+                    "highlight_end": 29
+                }
+            ],
+            "label": null,
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        }
+    ],
+    "children": [
+        {
+            "message": "lint level defined here",
+            "code": null,
+            "level": "note",
+            "spans": [
+                {
+                    "file_name": "compiler/lib.rs",
+                    "byte_start": 8,
+                    "byte_end": 19,
+                    "line_start": 1,
+                    "line_end": 1,
+                    "column_start": 9,
+                    "column_end": 20,
+                    "is_primary": true,
+                    "text": [
+                        {
+                            "text": "#![warn(clippy::all)]",
+                            "highlight_start": 9,
+                            "highlight_end": 20
+                        }
+                    ],
+                    "label": null,
+                    "suggested_replacement": null,
+                    "suggestion_applicability": null,
+                    "expansion": null
+                }
+            ],
+            "children": [],
+            "rendered": null
+        },
+        {
+            "message": "#[warn(clippy::trivially_copy_pass_by_ref)] implied by #[warn(clippy::all)]",
+            "code": null,
+            "level": "note",
+            "spans": [],
+            "children": [],
+            "rendered": null
+        },
+        {
+            "message": "for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref",
+            "code": null,
+            "level": "help",
+            "spans": [],
+            "children": [],
+            "rendered": null
+        },
+        {
+            "message": "consider passing by value instead",
+            "code": null,
+            "level": "help",
+            "spans": [
+                {
+                    "file_name": "compiler/mir/tagset.rs",
+                    "byte_start": 941,
+                    "byte_end": 946,
+                    "line_start": 42,
+                    "line_end": 42,
+                    "column_start": 24,
+                    "column_end": 29,
+                    "is_primary": true,
+                    "text": [
+                        {
+                            "text": "    pub fn is_disjoint(&self, other: Self) -> bool {",
+                            "highlight_start": 24,
+                            "highlight_end": 29
+                        }
+                    ],
+                    "label": null,
+                    "suggested_replacement": "self",
+                    "suggestion_applicability": "Unspecified",
+                    "expansion": null
+                }
+            ],
+            "children": [],
+            "rendered": null
+        }
+    ],
+    "rendered": "warning: this argument is passed by reference, but would be more efficient if passed by value\n  --> compiler/mir/tagset.rs:42:24\n   |\n42 |     pub fn is_disjoint(&self, other: Self) -> bool {\n   |                        ^^^^^ help: consider passing by value instead: `self`\n   |\nnote: lint level defined here\n  --> compiler/lib.rs:1:9\n   |\n1  | #![warn(clippy::all)]\n   |         ^^^^^^^^^^^\n   = note: #[warn(clippy::trivially_copy_pass_by_ref)] implied by #[warn(clippy::all)]\n   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref\n\n"
+    }"##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_rustc_mismatched_type() {
+        let diag = parse_diagnostic(
+            r##"{
+    "message": "mismatched types",
+    "code": {
+        "code": "E0308",
+        "explanation": "\nThis error occurs when the compiler was unable to infer the concrete type of a\nvariable. It can occur for several cases, the most common of which is a\nmismatch in the expected type that the compiler inferred for a variable's\ninitializing expression, and the actual type explicitly assigned to the\nvariable.\n\nFor example:\n\n```compile_fail,E0308\nlet x: i32 = \"I am not a number!\";\n//     ~~~   ~~~~~~~~~~~~~~~~~~~~\n//      |             |\n//      |    initializing expression;\n//      |    compiler infers type `&str`\n//      |\n//    type `i32` assigned to variable `x`\n```\n"
+    },
+    "level": "error",
+    "spans": [
+        {
+            "file_name": "runtime/compiler_support.rs",
+            "byte_start": 1589,
+            "byte_end": 1594,
+            "line_start": 48,
+            "line_end": 48,
+            "column_start": 65,
+            "column_end": 70,
+            "is_primary": true,
+            "text": [
+                {
+                    "text": "    let layout = alloc::Layout::from_size_align_unchecked(size, align);",
+                    "highlight_start": 65,
+                    "highlight_end": 70
+                }
+            ],
+            "label": "expected usize, found u32",
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "expansion": null
+        }
+    ],
+    "children": [],
+    "rendered": "error[E0308]: mismatched types\n  --> runtime/compiler_support.rs:48:65\n   |\n48 |     let layout = alloc::Layout::from_size_align_unchecked(size, align);\n   |                                                                 ^^^^^ expected usize, found u32\n\n"
+    }"##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_handles_macro_location() {
+        let diag = parse_diagnostic(
+            r##"{
+    "rendered": "error[E0277]: can't compare `{integer}` with `&str`\n --> src/main.rs:2:5\n  |\n2 |     assert_eq!(1, \"love\");\n  |     ^^^^^^^^^^^^^^^^^^^^^^ no implementation for `{integer} == &str`\n  |\n  = help: the trait `std::cmp::PartialEq<&str>` is not implemented for `{integer}`\n  = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)\n\n",
+    "children": [
+        {
+            "children": [],
+            "code": null,
+            "level": "help",
+            "message": "the trait `std::cmp::PartialEq<&str>` is not implemented for `{integer}`",
+            "rendered": null,
+            "spans": []
+        }
+    ],
+    "code": {
+        "code": "E0277",
+        "explanation": "\nYou tried to use a type which doesn't implement some trait in a place which\nexpected that trait. Erroneous code example:\n\n```compile_fail,E0277\n// here we declare the Foo trait with a bar method\ntrait Foo {\n    fn bar(&self);\n}\n\n// we now declare a function which takes an object implementing the Foo trait\nfn some_func<T: Foo>(foo: T) {\n    foo.bar();\n}\n\nfn main() {\n    // we now call the method with the i32 type, which doesn't implement\n    // the Foo trait\n    some_func(5i32); // error: the trait bound `i32 : Foo` is not satisfied\n}\n```\n\nIn order to fix this error, verify that the type you're using does implement\nthe trait. Example:\n\n```\ntrait Foo {\n    fn bar(&self);\n}\n\nfn some_func<T: Foo>(foo: T) {\n    foo.bar(); // we can now use this method since i32 implements the\n               // Foo trait\n}\n\n// we implement the trait on the i32 type\nimpl Foo for i32 {\n    fn bar(&self) {}\n}\n\nfn main() {\n    some_func(5i32); // ok!\n}\n```\n\nOr in a generic context, an erroneous code example would look like:\n\n```compile_fail,E0277\nfn some_func<T>(foo: T) {\n    println!(\"{:?}\", foo); // error: the trait `core::fmt::Debug` is not\n                           //        implemented for the type `T`\n}\n\nfn main() {\n    // We now call the method with the i32 type,\n    // which *does* implement the Debug trait.\n    some_func(5i32);\n}\n```\n\nNote that the error here is in the definition of the generic function: Although\nwe only call it with a parameter that does implement `Debug`, the compiler\nstill rejects the function: It must work with all possible input types. In\norder to make this example compile, we need to restrict the generic type we're\naccepting:\n\n```\nuse std::fmt;\n\n// Restrict the input type to types that implement Debug.\nfn some_func<T: fmt::Debug>(foo: T) {\n    println!(\"{:?}\", foo);\n}\n\nfn main() {\n    // Calling the method is still fine, as i32 implements Debug.\n    some_func(5i32);\n\n    // This would fail to compile now:\n    // struct WithoutDebug;\n    // some_func(WithoutDebug);\n}\n```\n\nRust only looks at the signature of the called function, as such it must\nalready specify all requirements that will be used for every type parameter.\n"
+    },
+    "level": "error",
+    "message": "can't compare `{integer}` with `&str`",
+    "spans": [
+        {
+            "byte_end": 155,
+            "byte_start": 153,
+            "column_end": 33,
+            "column_start": 31,
+            "expansion": {
+                "def_site_span": {
+                    "byte_end": 940,
+                    "byte_start": 0,
+                    "column_end": 6,
+                    "column_start": 1,
+                    "expansion": null,
+                    "file_name": "<::core::macros::assert_eq macros>",
+                    "is_primary": false,
+                    "label": null,
+                    "line_end": 36,
+                    "line_start": 1,
+                    "suggested_replacement": null,
+                    "suggestion_applicability": null,
+                    "text": [
+                        {
+                            "highlight_end": 35,
+                            "highlight_start": 1,
+                            "text": "($ left : expr, $ right : expr) =>"
+                        },
+                        {
+                            "highlight_end": 3,
+                            "highlight_start": 1,
+                            "text": "({"
+                        },
+                        {
+                            "highlight_end": 33,
+                            "highlight_start": 1,
+                            "text": "     match (& $ left, & $ right)"
+                        },
+                        {
+                            "highlight_end": 7,
+                            "highlight_start": 1,
+                            "text": "     {"
+                        },
+                        {
+                            "highlight_end": 34,
+                            "highlight_start": 1,
+                            "text": "         (left_val, right_val) =>"
+                        },
+                        {
+                            "highlight_end": 11,
+                            "highlight_start": 1,
+                            "text": "         {"
+                        },
+                        {
+                            "highlight_end": 46,
+                            "highlight_start": 1,
+                            "text": "             if ! (* left_val == * right_val)"
+                        },
+                        {
+                            "highlight_end": 15,
+                            "highlight_start": 1,
+                            "text": "             {"
+                        },
+                        {
+                            "highlight_end": 25,
+                            "highlight_start": 1,
+                            "text": "                 panic !"
+                        },
+                        {
+                            "highlight_end": 57,
+                            "highlight_start": 1,
+                            "text": "                 (r#\"assertion failed: `(left == right)`"
+                        },
+                        {
+                            "highlight_end": 16,
+                            "highlight_start": 1,
+                            "text": "  left: `{:?}`,"
+                        },
+                        {
+                            "highlight_end": 18,
+                            "highlight_start": 1,
+                            "text": " right: `{:?}`\"#,"
+                        },
+                        {
+                            "highlight_end": 47,
+                            "highlight_start": 1,
+                            "text": "                  & * left_val, & * right_val)"
+                        },
+                        {
+                            "highlight_end": 15,
+                            "highlight_start": 1,
+                            "text": "             }"
+                        },
+                        {
+                            "highlight_end": 11,
+                            "highlight_start": 1,
+                            "text": "         }"
+                        },
+                        {
+                            "highlight_end": 7,
+                            "highlight_start": 1,
+                            "text": "     }"
+                        },
+                        {
+                            "highlight_end": 42,
+                            "highlight_start": 1,
+                            "text": " }) ; ($ left : expr, $ right : expr,) =>"
+                        },
+                        {
+                            "highlight_end": 49,
+                            "highlight_start": 1,
+                            "text": "({ $ crate :: assert_eq ! ($ left, $ right) }) ;"
+                        },
+                        {
+                            "highlight_end": 53,
+                            "highlight_start": 1,
+                            "text": "($ left : expr, $ right : expr, $ ($ arg : tt) +) =>"
+                        },
+                        {
+                            "highlight_end": 3,
+                            "highlight_start": 1,
+                            "text": "({"
+                        },
+                        {
+                            "highlight_end": 37,
+                            "highlight_start": 1,
+                            "text": "     match (& ($ left), & ($ right))"
+                        },
+                        {
+                            "highlight_end": 7,
+                            "highlight_start": 1,
+                            "text": "     {"
+                        },
+                        {
+                            "highlight_end": 34,
+                            "highlight_start": 1,
+                            "text": "         (left_val, right_val) =>"
+                        },
+                        {
+                            "highlight_end": 11,
+                            "highlight_start": 1,
+                            "text": "         {"
+                        },
+                        {
+                            "highlight_end": 46,
+                            "highlight_start": 1,
+                            "text": "             if ! (* left_val == * right_val)"
+                        },
+                        {
+                            "highlight_end": 15,
+                            "highlight_start": 1,
+                            "text": "             {"
+                        },
+                        {
+                            "highlight_end": 25,
+                            "highlight_start": 1,
+                            "text": "                 panic !"
+                        },
+                        {
+                            "highlight_end": 57,
+                            "highlight_start": 1,
+                            "text": "                 (r#\"assertion failed: `(left == right)`"
+                        },
+                        {
+                            "highlight_end": 16,
+                            "highlight_start": 1,
+                            "text": "  left: `{:?}`,"
+                        },
+                        {
+                            "highlight_end": 22,
+                            "highlight_start": 1,
+                            "text": " right: `{:?}`: {}\"#,"
+                        },
+                        {
+                            "highlight_end": 72,
+                            "highlight_start": 1,
+                            "text": "                  & * left_val, & * right_val, $ crate :: format_args !"
+                        },
+                        {
+                            "highlight_end": 33,
+                            "highlight_start": 1,
+                            "text": "                  ($ ($ arg) +))"
+                        },
+                        {
+                            "highlight_end": 15,
+                            "highlight_start": 1,
+                            "text": "             }"
+                        },
+                        {
+                            "highlight_end": 11,
+                            "highlight_start": 1,
+                            "text": "         }"
+                        },
+                        {
+                            "highlight_end": 7,
+                            "highlight_start": 1,
+                            "text": "     }"
+                        },
+                        {
+                            "highlight_end": 6,
+                            "highlight_start": 1,
+                            "text": " }) ;"
+                        }
+                    ]
+                },
+                "macro_decl_name": "assert_eq!",
+                "span": {
+                    "byte_end": 38,
+                    "byte_start": 16,
+                    "column_end": 27,
+                    "column_start": 5,
+                    "expansion": null,
+                    "file_name": "src/main.rs",
+                    "is_primary": false,
+                    "label": null,
+                    "line_end": 2,
+                    "line_start": 2,
+                    "suggested_replacement": null,
+                    "suggestion_applicability": null,
+                    "text": [
+                        {
+                            "highlight_end": 27,
+                            "highlight_start": 5,
+                            "text": "    assert_eq!(1, \"love\");"
+                        }
+                    ]
+                }
+            },
+            "file_name": "<::core::macros::assert_eq macros>",
+            "is_primary": true,
+            "label": "no implementation for `{integer} == &str`",
+            "line_end": 7,
+            "line_start": 7,
+            "suggested_replacement": null,
+            "suggestion_applicability": null,
+            "text": [
+                {
+                    "highlight_end": 33,
+                    "highlight_start": 31,
+                    "text": "             if ! (* left_val == * right_val)"
+                }
+            ]
+        }
+    ]
+    }"##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_macro_compiler_error() {
+        let diag = parse_diagnostic(
+            r##"{
+        "rendered": "error: Please register your known path in the path module\n   --> crates/ra_hir_def/src/path.rs:265:9\n    |\n265 |         compile_error!(\"Please register your known path in the path module\")\n    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n    | \n   ::: crates/ra_hir_def/src/data.rs:80:16\n    |\n80  |     let path = path![std::future::Future];\n    |                -------------------------- in this macro invocation\n\n",
+        "children": [],
+        "code": null,
+        "level": "error",
+        "message": "Please register your known path in the path module",
+        "spans": [
+            {
+                "byte_end": 8285,
+                "byte_start": 8217,
+                "column_end": 77,
+                "column_start": 9,
+                "expansion": {
+                    "def_site_span": {
+                        "byte_end": 8294,
+                        "byte_start": 7858,
+                        "column_end": 2,
+                        "column_start": 1,
+                        "expansion": null,
+                        "file_name": "crates/ra_hir_def/src/path.rs",
+                        "is_primary": false,
+                        "label": null,
+                        "line_end": 267,
+                        "line_start": 254,
+                        "suggested_replacement": null,
+                        "suggestion_applicability": null,
+                        "text": [
+                            {
+                                "highlight_end": 28,
+                                "highlight_start": 1,
+                                "text": "macro_rules! __known_path {"
+                            },
+                            {
+                                "highlight_end": 37,
+                                "highlight_start": 1,
+                                "text": "    (std::iter::IntoIterator) => {};"
+                            },
+                            {
+                                "highlight_end": 33,
+                                "highlight_start": 1,
+                                "text": "    (std::result::Result) => {};"
+                            },
+                            {
+                                "highlight_end": 29,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::Range) => {};"
+                            },
+                            {
+                                "highlight_end": 33,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::RangeFrom) => {};"
+                            },
+                            {
+                                "highlight_end": 33,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::RangeFull) => {};"
+                            },
+                            {
+                                "highlight_end": 31,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::RangeTo) => {};"
+                            },
+                            {
+                                "highlight_end": 40,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::RangeToInclusive) => {};"
+                            },
+                            {
+                                "highlight_end": 38,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::RangeInclusive) => {};"
+                            },
+                            {
+                                "highlight_end": 27,
+                                "highlight_start": 1,
+                                "text": "    (std::ops::Try) => {};"
+                            },
+                            {
+                                "highlight_end": 22,
+                                "highlight_start": 1,
+                                "text": "    ($path:path) => {"
+                            },
+                            {
+                                "highlight_end": 77,
+                                "highlight_start": 1,
+                                "text": "        compile_error!(\"Please register your known path in the path module\")"
+                            },
+                            {
+                                "highlight_end": 7,
+                                "highlight_start": 1,
+                                "text": "    };"
+                            },
+                            {
+                                "highlight_end": 2,
+                                "highlight_start": 1,
+                                "text": "}"
+                            }
+                        ]
+                    },
+                    "macro_decl_name": "$crate::__known_path!",
+                    "span": {
+                        "byte_end": 8427,
+                        "byte_start": 8385,
+                        "column_end": 51,
+                        "column_start": 9,
+                        "expansion": {
+                            "def_site_span": {
+                                "byte_end": 8611,
+                                "byte_start": 8312,
+                                "column_end": 2,
+                                "column_start": 1,
+                                "expansion": null,
+                                "file_name": "crates/ra_hir_def/src/path.rs",
+                                "is_primary": false,
+                                "label": null,
+                                "line_end": 277,
+                                "line_start": 270,
+                                "suggested_replacement": null,
+                                "suggestion_applicability": null,
+                                "text": [
+                                    {
+                                        "highlight_end": 22,
+                                        "highlight_start": 1,
+                                        "text": "macro_rules! __path {"
+                                    },
+                                    {
+                                        "highlight_end": 43,
+                                        "highlight_start": 1,
+                                        "text": "    ($start:ident $(:: $seg:ident)*) => ({"
+                                    },
+                                    {
+                                        "highlight_end": 51,
+                                        "highlight_start": 1,
+                                        "text": "        $crate::__known_path!($start $(:: $seg)*);"
+                                    },
+                                    {
+                                        "highlight_end": 87,
+                                        "highlight_start": 1,
+                                        "text": "        $crate::path::ModPath::from_simple_segments($crate::path::PathKind::Abs, vec!["
+                                    },
+                                    {
+                                        "highlight_end": 76,
+                                        "highlight_start": 1,
+                                        "text": "            $crate::path::__name![$start], $($crate::path::__name![$seg],)*"
+                                    },
+                                    {
+                                        "highlight_end": 11,
+                                        "highlight_start": 1,
+                                        "text": "        ])"
+                                    },
+                                    {
+                                        "highlight_end": 8,
+                                        "highlight_start": 1,
+                                        "text": "    });"
+                                    },
+                                    {
+                                        "highlight_end": 2,
+                                        "highlight_start": 1,
+                                        "text": "}"
+                                    }
+                                ]
+                            },
+                            "macro_decl_name": "path!",
+                            "span": {
+                                "byte_end": 2966,
+                                "byte_start": 2940,
+                                "column_end": 42,
+                                "column_start": 16,
+                                "expansion": null,
+                                "file_name": "crates/ra_hir_def/src/data.rs",
+                                "is_primary": false,
+                                "label": null,
+                                "line_end": 80,
+                                "line_start": 80,
+                                "suggested_replacement": null,
+                                "suggestion_applicability": null,
+                                "text": [
+                                    {
+                                        "highlight_end": 42,
+                                        "highlight_start": 16,
+                                        "text": "    let path = path![std::future::Future];"
+                                    }
+                                ]
+                            }
+                        },
+                        "file_name": "crates/ra_hir_def/src/path.rs",
+                        "is_primary": false,
+                        "label": null,
+                        "line_end": 272,
+                        "line_start": 272,
+                        "suggested_replacement": null,
+                        "suggestion_applicability": null,
+                        "text": [
+                            {
+                                "highlight_end": 51,
+                                "highlight_start": 9,
+                                "text": "        $crate::__known_path!($start $(:: $seg)*);"
+                            }
+                        ]
+                    }
+                },
+                "file_name": "crates/ra_hir_def/src/path.rs",
+                "is_primary": true,
+                "label": null,
+                "line_end": 265,
+                "line_start": 265,
+                "suggested_replacement": null,
+                "suggestion_applicability": null,
+                "text": [
+                    {
+                        "highlight_end": 77,
+                        "highlight_start": 9,
+                        "text": "        compile_error!(\"Please register your known path in the path module\")"
+                    }
+                ]
+            }
+        ]
+    }
+            "##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+
+    #[test]
+    #[cfg(not(windows))]
+    fn snap_multi_line_fix() {
+        let diag = parse_diagnostic(
+            r##"{
+                "rendered": "warning: returning the result of a let binding from a block\n --> src/main.rs:4:5\n  |\n3 |     let a = (0..10).collect();\n  |     -------------------------- unnecessary let binding\n4 |     a\n  |     ^\n  |\n  = note: `#[warn(clippy::let_and_return)]` on by default\n  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return\nhelp: return the expression directly\n  |\n3 |     \n4 |     (0..10).collect()\n  |\n\n",
+                "children": [
+                    {
+                    "children": [],
+                    "code": null,
+                    "level": "note",
+                    "message": "`#[warn(clippy::let_and_return)]` on by default",
+                    "rendered": null,
+                    "spans": []
+                    },
+                    {
+                    "children": [],
+                    "code": null,
+                    "level": "help",
+                    "message": "for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return",
+                    "rendered": null,
+                    "spans": []
+                    },
+                    {
+                    "children": [],
+                    "code": null,
+                    "level": "help",
+                    "message": "return the expression directly",
+                    "rendered": null,
+                    "spans": [
+                        {
+                        "byte_end": 55,
+                        "byte_start": 29,
+                        "column_end": 31,
+                        "column_start": 5,
+                        "expansion": null,
+                        "file_name": "src/main.rs",
+                        "is_primary": true,
+                        "label": null,
+                        "line_end": 3,
+                        "line_start": 3,
+                        "suggested_replacement": "",
+                        "suggestion_applicability": "MachineApplicable",
+                        "text": [
+                            {
+                            "highlight_end": 31,
+                            "highlight_start": 5,
+                            "text": "    let a = (0..10).collect();"
+                            }
+                        ]
+                        },
+                        {
+                        "byte_end": 61,
+                        "byte_start": 60,
+                        "column_end": 6,
+                        "column_start": 5,
+                        "expansion": null,
+                        "file_name": "src/main.rs",
+                        "is_primary": true,
+                        "label": null,
+                        "line_end": 4,
+                        "line_start": 4,
+                        "suggested_replacement": "(0..10).collect()",
+                        "suggestion_applicability": "MachineApplicable",
+                        "text": [
+                            {
+                            "highlight_end": 6,
+                            "highlight_start": 5,
+                            "text": "    a"
+                            }
+                        ]
+                        }
+                    ]
+                    }
+                ],
+                "code": {
+                    "code": "clippy::let_and_return",
+                    "explanation": null
+                },
+                "level": "warning",
+                "message": "returning the result of a let binding from a block",
+                "spans": [
+                    {
+                    "byte_end": 55,
+                    "byte_start": 29,
+                    "column_end": 31,
+                    "column_start": 5,
+                    "expansion": null,
+                    "file_name": "src/main.rs",
+                    "is_primary": false,
+                    "label": "unnecessary let binding",
+                    "line_end": 3,
+                    "line_start": 3,
+                    "suggested_replacement": null,
+                    "suggestion_applicability": null,
+                    "text": [
+                        {
+                        "highlight_end": 31,
+                        "highlight_start": 5,
+                        "text": "    let a = (0..10).collect();"
+                        }
+                    ]
+                    },
+                    {
+                    "byte_end": 61,
+                    "byte_start": 60,
+                    "column_end": 6,
+                    "column_start": 5,
+                    "expansion": null,
+                    "file_name": "src/main.rs",
+                    "is_primary": true,
+                    "label": null,
+                    "line_end": 4,
+                    "line_start": 4,
+                    "suggested_replacement": null,
+                    "suggestion_applicability": null,
+                    "text": [
+                        {
+                        "highlight_end": 6,
+                        "highlight_start": 5,
+                        "text": "    a"
+                        }
+                    ]
+                    }
+                ]
+            }
+            "##,
+        );
+
+        let workspace_root = Path::new("/test/");
+        let diag = map_rust_diagnostic_to_lsp(&diag, workspace_root);
+        insta::assert_debug_snapshot!(diag);
+    }
+}
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 13d305b97..15e5bb354 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -25,7 +25,7 @@ use lsp_types::{
     WorkDoneProgressBegin, WorkDoneProgressCreateParams, WorkDoneProgressEnd,
     WorkDoneProgressReport,
 };
-use ra_flycheck::{url_from_path_with_drive_lowercasing, CheckTask};
+use ra_flycheck::{CheckTask, Status};
 use ra_ide::{Canceled, FileId, LibraryData, LineIndex, SourceRootId};
 use ra_prof::profile;
 use ra_project_model::{PackageRoot, ProjectWorkspace};
@@ -37,7 +37,7 @@ use threadpool::ThreadPool;
 
 use crate::{
     config::{Config, FilesWatcher},
-    diagnostics::DiagnosticTask,
+    diagnostics::{to_proto::url_from_path_with_drive_lowercasing, DiagnosticTask},
     from_proto, lsp_ext,
     main_loop::{
         pending_requests::{PendingRequest, PendingRequests},
@@ -736,22 +736,61 @@ fn on_check_task(
             task_sender.send(Task::Diagnostic(DiagnosticTask::ClearCheck))?;
         }
 
-        CheckTask::AddDiagnostic { url, diagnostic, fixes } => {
-            let path = url.to_file_path().map_err(|()| format!("invalid uri: {}", url))?;
-            let file_id = match world_state.vfs.read().path2file(&path) {
-                Some(file) => FileId(file.0),
-                None => {
-                    log::error!("File with cargo diagnostic not found in VFS: {}", path.display());
-                    return Ok(());
-                }
-            };
+        CheckTask::AddDiagnostic { workspace_root, diagnostic } => {
+            let diagnostics = crate::diagnostics::to_proto::map_rust_diagnostic_to_lsp(
+                &diagnostic,
+                &workspace_root,
+            );
+            for diag in diagnostics {
+                let path = diag
+                    .location
+                    .uri
+                    .to_file_path()
+                    .map_err(|()| format!("invalid uri: {}", diag.location.uri))?;
+                let file_id = match world_state.vfs.read().path2file(&path) {
+                    Some(file) => FileId(file.0),
+                    None => {
+                        log::error!(
+                            "File with cargo diagnostic not found in VFS: {}",
+                            path.display()
+                        );
+                        return Ok(());
+                    }
+                };
 
-            task_sender
-                .send(Task::Diagnostic(DiagnosticTask::AddCheck(file_id, diagnostic, fixes)))?;
+                task_sender.send(Task::Diagnostic(DiagnosticTask::AddCheck(
+                    file_id,
+                    diag.diagnostic,
+                    diag.fixes.into_iter().map(|it| it.into()).collect(),
+                )))?;
+            }
         }
 
-        CheckTask::Status(progress) => {
+        CheckTask::Status(status) => {
             if world_state.config.client_caps.work_done_progress {
+                let progress = match status {
+                    Status::Being => {
+                        lsp_types::WorkDoneProgress::Begin(lsp_types::WorkDoneProgressBegin {
+                            title: "Running `cargo check`".to_string(),
+                            cancellable: Some(false),
+                            message: None,
+                            percentage: None,
+                        })
+                    }
+                    Status::Progress(target) => {
+                        lsp_types::WorkDoneProgress::Report(lsp_types::WorkDoneProgressReport {
+                            cancellable: Some(false),
+                            message: Some(target),
+                            percentage: None,
+                        })
+                    }
+                    Status::End => {
+                        lsp_types::WorkDoneProgress::End(lsp_types::WorkDoneProgressEnd {
+                            message: None,
+                        })
+                    }
+                };
+
                 let params = lsp_types::ProgressParams {
                     token: lsp_types::ProgressToken::String(
                         "rustAnalyzer/cargoWatcher".to_string(),
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 33c2fd595..a8e2e535f 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -164,27 +164,27 @@ pub(crate) fn completion_item(
         additional_text_edits: Some(additional_text_edits),
         documentation: completion_item.documentation().map(documentation),
         deprecated: Some(completion_item.deprecated()),
-        command: if completion_item.trigger_call_info() {
-            let cmd = lsp_types::Command {
-                title: "triggerParameterHints".into(),
-                command: "editor.action.triggerParameterHints".into(),
-                arguments: None,
-            };
-            Some(cmd)
-        } else {
-            None
-        },
         ..Default::default()
     };
 
     if completion_item.score().is_some() {
-        res.preselect = Some(true)
+        res.preselect = Some(true);
+        // HACK: sort preselect items first
+        res.sort_text = Some(format!(" {}", completion_item.label()));
     }
 
     if completion_item.deprecated() {
         res.tags = Some(vec![lsp_types::CompletionItemTag::Deprecated])
     }
 
+    if completion_item.trigger_call_info() {
+        res.command = Some(lsp_types::Command {
+            title: "triggerParameterHints".into(),
+            command: "editor.action.triggerParameterHints".into(),
+            arguments: None,
+        });
+    }
+
     res.insert_text_format = Some(insert_text_format(completion_item.insert_text_format()));
 
     res
diff --git a/crates/rust-analyzer/src/world.rs b/crates/rust-analyzer/src/world.rs
index 6333c15b2..367272925 100644
--- a/crates/rust-analyzer/src/world.rs
+++ b/crates/rust-analyzer/src/world.rs
@@ -11,7 +11,7 @@ use std::{
 use crossbeam_channel::{unbounded, Receiver};
 use lsp_types::Url;
 use parking_lot::RwLock;
-use ra_flycheck::{url_from_path_with_drive_lowercasing, Flycheck, FlycheckConfig};
+use ra_flycheck::{Flycheck, FlycheckConfig};
 use ra_ide::{
     Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData, SourceRootId,
 };
@@ -22,7 +22,9 @@ use stdx::format_to;
 
 use crate::{
     config::Config,
-    diagnostics::{CheckFixes, DiagnosticCollection},
+    diagnostics::{
+        to_proto::url_from_path_with_drive_lowercasing, CheckFixes, DiagnosticCollection,
+    },
     main_loop::pending_requests::{CompletedRequest, LatestRequests},
     vfs_glob::{Glob, RustPackageFilterBuilder},
     LspError, Result,