17 files changed, 774 insertions, 105 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 45804c087..f1651edaa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1247,6 +1247,7 @@ dependencies = [
 name = "ra_project_model"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "cargo_metadata",
  "log",
  "ra_arena",
diff --git a/crates/ra_assists/src/handlers/auto_import.rs b/crates/ra_assists/src/handlers/auto_import.rs
index 1fb701da5..c4aea2a06 100644
--- a/crates/ra_assists/src/handlers/auto_import.rs
+++ b/crates/ra_assists/src/handlers/auto_import.rs
@@ -1,10 +1,18 @@
-use ra_ide_db::imports_locator::ImportsLocator;
-use ra_syntax::ast::{self, AstNode};
-
 use crate::{
     assist_ctx::{Assist, AssistCtx},
     insert_use_statement, AssistId,
 };
+use hir::{
+    db::HirDatabase, AsAssocItem, AssocItemContainer, ModPath, Module, ModuleDef, PathResolution,
+    SourceAnalyzer, Trait, Type,
+};
+use ra_ide_db::{imports_locator::ImportsLocator, RootDatabase};
+use ra_prof::profile;
+use ra_syntax::{
+    ast::{self, AstNode},
+    SyntaxNode,
+};
+use rustc_hash::FxHashSet;
 use std::collections::BTreeSet;
 
 // Assist: auto_import
@@ -27,52 +35,24 @@ use std::collections::BTreeSet;
 // # pub mod std { pub mod collections { pub struct HashMap { } } }
 // ```
 pub(crate) fn auto_import(ctx: AssistCtx) -> Option<Assist> {
-    let path_under_caret: ast::Path = ctx.find_node_at_offset()?;
-    if path_under_caret.syntax().ancestors().find_map(ast::UseItem::cast).is_some() {
-        return None;
-    }
-
-    let module = path_under_caret.syntax().ancestors().find_map(ast::Module::cast);
-    let position = match module.and_then(|it| it.item_list()) {
-        Some(item_list) => item_list.syntax().clone(),
-        None => {
-            let current_file =
-                path_under_caret.syntax().ancestors().find_map(ast::SourceFile::cast)?;
-            current_file.syntax().clone()
-        }
-    };
-    let source_analyzer = ctx.source_analyzer(&position, None);
-    let module_with_name_to_import = source_analyzer.module()?;
-
-    let name_ref_to_import =
-        path_under_caret.syntax().descendants().find_map(ast::NameRef::cast)?;
-    if source_analyzer
-        .resolve_path(ctx.db, &name_ref_to_import.syntax().ancestors().find_map(ast::Path::cast)?)
-        .is_some()
-    {
-        return None;
-    }
-
-    let name_to_import = name_ref_to_import.syntax().to_string();
-    let proposed_imports = ImportsLocator::new(ctx.db)
-        .find_imports(&name_to_import)
-        .into_iter()
-        .filter_map(|module_def| module_with_name_to_import.find_use_path(ctx.db, module_def))
-        .filter(|use_path| !use_path.segments.is_empty())
-        .take(20)
-        .collect::<BTreeSet<_>>();
-
+    let auto_import_assets = AutoImportAssets::new(&ctx)?;
+    let proposed_imports = auto_import_assets.search_for_imports(ctx.db);
     if proposed_imports.is_empty() {
         return None;
     }
 
-    let mut group = ctx.add_assist_group(format!("Import {}", name_to_import));
+    let assist_group_name = if proposed_imports.len() == 1 {
+        format!("Import `{}`", proposed_imports.iter().next().unwrap())
+    } else {
+        auto_import_assets.get_import_group_message()
+    };
+    let mut group = ctx.add_assist_group(assist_group_name);
     for import in proposed_imports {
         group.add_assist(AssistId("auto_import"), format!("Import `{}`", &import), |edit| {
-            edit.target(path_under_caret.syntax().text_range());
+            edit.target(auto_import_assets.syntax_under_caret.text_range());
             insert_use_statement(
-                &position,
-                path_under_caret.syntax(),
+                &auto_import_assets.syntax_under_caret,
+                &auto_import_assets.syntax_under_caret,
                 &import,
                 edit.text_edit_builder(),
             );
@@ -81,11 +61,232 @@ pub(crate) fn auto_import(ctx: AssistCtx) -> Option<Assist> {
     group.finish()
 }
 
+struct AutoImportAssets {
+    import_candidate: ImportCandidate,
+    module_with_name_to_import: Module,
+    syntax_under_caret: SyntaxNode,
+}
+
+impl AutoImportAssets {
+    fn new(ctx: &AssistCtx) -> Option<Self> {
+        if let Some(path_under_caret) = ctx.find_node_at_offset::<ast::Path>() {
+            Self::for_regular_path(path_under_caret, &ctx)
+        } else {
+            Self::for_method_call(ctx.find_node_at_offset()?, &ctx)
+        }
+    }
+
+    fn for_method_call(method_call: ast::MethodCallExpr, ctx: &AssistCtx) -> Option<Self> {
+        let syntax_under_caret = method_call.syntax().to_owned();
+        let source_analyzer = ctx.source_analyzer(&syntax_under_caret, None);
+        let module_with_name_to_import = source_analyzer.module()?;
+        Some(Self {
+            import_candidate: ImportCandidate::for_method_call(
+                &method_call,
+                &source_analyzer,
+                ctx.db,
+            )?,
+            module_with_name_to_import,
+            syntax_under_caret,
+        })
+    }
+
+    fn for_regular_path(path_under_caret: ast::Path, ctx: &AssistCtx) -> Option<Self> {
+        let syntax_under_caret = path_under_caret.syntax().to_owned();
+        if syntax_under_caret.ancestors().find_map(ast::UseItem::cast).is_some() {
+            return None;
+        }
+
+        let source_analyzer = ctx.source_analyzer(&syntax_under_caret, None);
+        let module_with_name_to_import = source_analyzer.module()?;
+        Some(Self {
+            import_candidate: ImportCandidate::for_regular_path(
+                &path_under_caret,
+                &source_analyzer,
+                ctx.db,
+            )?,
+            module_with_name_to_import,
+            syntax_under_caret,
+        })
+    }
+
+    fn get_search_query(&self) -> &str {
+        match &self.import_candidate {
+            ImportCandidate::UnqualifiedName(name) => name,
+            ImportCandidate::QualifierStart(qualifier_start) => qualifier_start,
+            ImportCandidate::TraitAssocItem(_, trait_assoc_item_name) => trait_assoc_item_name,
+            ImportCandidate::TraitMethod(_, trait_method_name) => trait_method_name,
+        }
+    }
+
+    fn get_import_group_message(&self) -> String {
+        match &self.import_candidate {
+            ImportCandidate::UnqualifiedName(name) => format!("Import {}", name),
+            ImportCandidate::QualifierStart(qualifier_start) => {
+                format!("Import {}", qualifier_start)
+            }
+            ImportCandidate::TraitAssocItem(_, trait_assoc_item_name) => {
+                format!("Import a trait for item {}", trait_assoc_item_name)
+            }
+            ImportCandidate::TraitMethod(_, trait_method_name) => {
+                format!("Import a trait for method {}", trait_method_name)
+            }
+        }
+    }
+
+    fn search_for_imports(&self, db: &RootDatabase) -> BTreeSet<ModPath> {
+        let _p = profile("auto_import::search_for_imports");
+        let current_crate = self.module_with_name_to_import.krate();
+        ImportsLocator::new(db)
+            .find_imports(&self.get_search_query())
+            .into_iter()
+            .filter_map(|module_def| match &self.import_candidate {
+                ImportCandidate::TraitAssocItem(assoc_item_type, _) => {
+                    let located_assoc_item = match module_def {
+                        ModuleDef::Function(located_function) => located_function
+                            .as_assoc_item(db)
+                            .map(|assoc| assoc.container(db))
+                            .and_then(Self::assoc_to_trait),
+                        ModuleDef::Const(located_const) => located_const
+                            .as_assoc_item(db)
+                            .map(|assoc| assoc.container(db))
+                            .and_then(Self::assoc_to_trait),
+                        _ => None,
+                    }?;
+
+                    let mut trait_candidates = FxHashSet::default();
+                    trait_candidates.insert(located_assoc_item.into());
+
+                    assoc_item_type
+                        .iterate_path_candidates(
+                            db,
+                            current_crate,
+                            &trait_candidates,
+                            None,
+                            |_, assoc| Self::assoc_to_trait(assoc.container(db)),
+                        )
+                        .map(ModuleDef::from)
+                }
+                ImportCandidate::TraitMethod(function_callee, _) => {
+                    let located_assoc_item =
+                        if let ModuleDef::Function(located_function) = module_def {
+                            located_function
+                                .as_assoc_item(db)
+                                .map(|assoc| assoc.container(db))
+                                .and_then(Self::assoc_to_trait)
+                        } else {
+                            None
+                        }?;
+
+                    let mut trait_candidates = FxHashSet::default();
+                    trait_candidates.insert(located_assoc_item.into());
+
+                    function_callee
+                        .iterate_method_candidates(
+                            db,
+                            current_crate,
+                            &trait_candidates,
+                            None,
+                            |_, function| {
+                                Self::assoc_to_trait(function.as_assoc_item(db)?.container(db))
+                            },
+                        )
+                        .map(ModuleDef::from)
+                }
+                _ => Some(module_def),
+            })
+            .filter_map(|module_def| self.module_with_name_to_import.find_use_path(db, module_def))
+            .filter(|use_path| !use_path.segments.is_empty())
+            .take(20)
+            .collect::<BTreeSet<_>>()
+    }
+
+    fn assoc_to_trait(assoc: AssocItemContainer) -> Option<Trait> {
+        if let AssocItemContainer::Trait(extracted_trait) = assoc {
+            Some(extracted_trait)
+        } else {
+            None
+        }
+    }
+}
+
+#[derive(Debug)]
+enum ImportCandidate {
+    /// Simple name like 'HashMap'
+    UnqualifiedName(String),
+    /// First part of the qualified name.
+    /// For 'std::collections::HashMap', that will be 'std'.
+    QualifierStart(String),
+    /// A trait associated function (with no self parameter) or associated constant.
+    /// For 'test_mod::TestEnum::test_function', `Type` is the `test_mod::TestEnum` expression type
+    /// and `String` is the `test_function`
+    TraitAssocItem(Type, String),
+    /// A trait method with self parameter.
+    /// For 'test_enum.test_method()', `Type` is the `test_enum` expression type
+    /// and `String` is the `test_method`
+    TraitMethod(Type, String),
+}
+
+impl ImportCandidate {
+    fn for_method_call(
+        method_call: &ast::MethodCallExpr,
+        source_analyzer: &SourceAnalyzer,
+        db: &impl HirDatabase,
+    ) -> Option<Self> {
+        if source_analyzer.resolve_method_call(method_call).is_some() {
+            return None;
+        }
+        Some(Self::TraitMethod(
+            source_analyzer.type_of(db, &method_call.expr()?)?,
+            method_call.name_ref()?.syntax().to_string(),
+        ))
+    }
+
+    fn for_regular_path(
+        path_under_caret: &ast::Path,
+        source_analyzer: &SourceAnalyzer,
+        db: &impl HirDatabase,
+    ) -> Option<Self> {
+        if source_analyzer.resolve_path(db, path_under_caret).is_some() {
+            return None;
+        }
+
+        let segment = path_under_caret.segment()?;
+        if let Some(qualifier) = path_under_caret.qualifier() {
+            let qualifier_start = qualifier.syntax().descendants().find_map(ast::NameRef::cast)?;
+            let qualifier_start_path =
+                qualifier_start.syntax().ancestors().find_map(ast::Path::cast)?;
+            if let Some(qualifier_start_resolution) =
+                source_analyzer.resolve_path(db, &qualifier_start_path)
+            {
+                let qualifier_resolution = if qualifier_start_path == qualifier {
+                    qualifier_start_resolution
+                } else {
+                    source_analyzer.resolve_path(db, &qualifier)?
+                };
+                if let PathResolution::Def(ModuleDef::Adt(assoc_item_path)) = qualifier_resolution {
+                    Some(ImportCandidate::TraitAssocItem(
+                        assoc_item_path.ty(db),
+                        segment.syntax().to_string(),
+                    ))
+                } else {
+                    None
+                }
+            } else {
+                Some(ImportCandidate::QualifierStart(qualifier_start.syntax().to_string()))
+            }
+        } else {
+            Some(ImportCandidate::UnqualifiedName(
+                segment.syntax().descendants().find_map(ast::NameRef::cast)?.syntax().to_string(),
+            ))
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::helpers::{check_assist, check_assist_not_applicable, check_assist_target};
-
     use super::*;
+    use crate::helpers::{check_assist, check_assist_not_applicable, check_assist_target};
 
     #[test]
     fn applicable_when_found_an_import() {
@@ -290,4 +491,303 @@ mod tests {
             ",
         );
     }
+
+    #[test]
+    fn not_applicable_for_imported_function() {
+        check_assist_not_applicable(
+            auto_import,
+            r"
+            pub mod test_mod {
+                pub fn test_function() {}
+            }
+
+            use test_mod::test_function;
+            fn main() {
+                test_function<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_struct_function() {
+        check_assist(
+            auto_import,
+            r"
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    pub fn test_function() {}
+                }
+            }
+
+            fn main() {
+                TestStruct::test_function<|>
+            }
+            ",
+            r"
+            use test_mod::TestStruct;
+
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    pub fn test_function() {}
+                }
+            }
+
+            fn main() {
+                TestStruct::test_function<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_struct_const() {
+        check_assist(
+            auto_import,
+            r"
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                TestStruct::TEST_CONST<|>
+            }
+            ",
+            r"
+            use test_mod::TestStruct;
+
+            mod test_mod {
+                pub struct TestStruct {}
+                impl TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                TestStruct::TEST_CONST<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn associated_trait_function() {
+        check_assist(
+            auto_import,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_function() {}
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::test_function<|>
+            }
+            ",
+            r"
+            use test_mod::TestTrait;
+
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_function() {}
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::test_function<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_trait_for_function() {
+        check_assist_not_applicable(
+            auto_import,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_function();
+                }
+                pub trait TestTrait2 {
+                    fn test_function();
+                }
+                pub enum TestEnum {
+                    One,
+                    Two,
+                }
+                impl TestTrait2 for TestEnum {
+                    fn test_function() {}
+                }
+                impl TestTrait for TestEnum {
+                    fn test_function() {}
+                }
+            }
+
+            use test_mod::TestTrait2;
+            fn main() {
+                test_mod::TestEnum::test_function<|>;
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn associated_trait_const() {
+        check_assist(
+            auto_import,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::TEST_CONST<|>
+            }
+            ",
+            r"
+            use test_mod::TestTrait;
+
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            fn main() {
+                test_mod::TestStruct::TEST_CONST<|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_trait_for_const() {
+        check_assist_not_applicable(
+            auto_import,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    const TEST_CONST: u8;
+                }
+                pub trait TestTrait2 {
+                    const TEST_CONST: f64;
+                }
+                pub enum TestEnum {
+                    One,
+                    Two,
+                }
+                impl TestTrait2 for TestEnum {
+                    const TEST_CONST: f64 = 42.0;
+                }
+                impl TestTrait for TestEnum {
+                    const TEST_CONST: u8 = 42;
+                }
+            }
+
+            use test_mod::TestTrait2;
+            fn main() {
+                test_mod::TestEnum::TEST_CONST<|>;
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn trait_method() {
+        check_assist(
+            auto_import,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_struct.test_meth<|>od()
+            }
+            ",
+            r"
+            use test_mod::TestTrait;
+
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub struct TestStruct {}
+                impl TestTrait for TestStruct {
+                    fn test_method(&self) {}
+                }
+            }
+
+            fn main() {
+                let test_struct = test_mod::TestStruct {};
+                test_struct.test_meth<|>od()
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn not_applicable_for_imported_trait_for_method() {
+        check_assist_not_applicable(
+            auto_import,
+            r"
+            mod test_mod {
+                pub trait TestTrait {
+                    fn test_method(&self);
+                }
+                pub trait TestTrait2 {
+                    fn test_method(&self);
+                }
+                pub enum TestEnum {
+                    One,
+                    Two,
+                }
+                impl TestTrait2 for TestEnum {
+                    fn test_method(&self) {}
+                }
+                impl TestTrait for TestEnum {
+                    fn test_method(&self) {}
+                }
+            }
+
+            use test_mod::TestTrait2;
+            fn main() {
+                let one = test_mod::TestEnum::One;
+                one.test<|>_method();
+            }
+            ",
+        )
+    }
 }
diff --git a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
index b70c88ec2..eac452413 100644
--- a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
@@ -431,7 +431,12 @@ fn best_action_for_target(
                 .find(|n| n.text_range().start() < anchor.text_range().start())
                 .or_else(|| Some(anchor));
 
-            ImportAction::add_new_use(anchor, false)
+            let add_after_anchor = anchor
+                .clone()
+                .and_then(ast::Attr::cast)
+                .map(|attr| attr.kind() == ast::AttrKind::Inner)
+                .unwrap_or(false);
+            ImportAction::add_new_use(anchor, add_after_anchor)
         }
     }
 }
@@ -962,4 +967,26 @@ mod foo {
     ",
         );
     }
+
+    #[test]
+    fn inserts_imports_after_inner_attributes() {
+        check_assist(
+            replace_qualified_name_with_use,
+            "
+#![allow(dead_code)]
+
+fn main() {
+    std::fmt::Debug<|>
+}
+    ",
+            "
+#![allow(dead_code)]
+use std::fmt::Debug;
+
+fn main() {
+    Debug<|>
+}
+    ",
+        );
+    }
 }
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 4d9641728..a56b8ab04 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -10,9 +10,9 @@ use hir_def::{
     per_ns::PerNs,
     resolver::HasResolver,
     type_ref::{Mutability, TypeRef},
-    AdtId, ConstId, DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule, ImplId,
-    LocalEnumVariantId, LocalModuleId, LocalStructFieldId, Lookup, ModuleId, StaticId, StructId,
-    TraitId, TypeAliasId, TypeParamId, UnionId,
+    AdtId, AssocContainerId, ConstId, DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule,
+    ImplId, LocalEnumVariantId, LocalModuleId, LocalStructFieldId, Lookup, ModuleId, StaticId,
+    StructId, TraitId, TypeAliasId, TypeParamId, UnionId,
 };
 use hir_expand::{
     diagnostics::DiagnosticSink,
@@ -25,7 +25,10 @@ use hir_ty::{
 };
 use ra_db::{CrateId, Edition, FileId};
 use ra_prof::profile;
-use ra_syntax::ast::{self, AttrsOwner};
+use ra_syntax::{
+    ast::{self, AttrsOwner},
+    AstNode,
+};
 
 use crate::{
     db::{DefDatabase, HirDatabase},
@@ -119,7 +122,9 @@ impl_froms!(
     BuiltinType
 );
 
-pub use hir_def::{attr::Attrs, item_scope::ItemInNs, visibility::Visibility, AssocItemId};
+pub use hir_def::{
+    attr::Attrs, item_scope::ItemInNs, visibility::Visibility, AssocItemId, AssocItemLoc,
+};
 use rustc_hash::FxHashSet;
 
 impl Module {
@@ -639,17 +644,49 @@ pub struct MacroDef {
     pub(crate) id: MacroDefId,
 }
 
+/// Invariant: `inner.as_assoc_item(db).is_some()`
+/// We do not actively enforce this invariant.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum AssocItem {
     Function(Function),
     Const(Const),
     TypeAlias(TypeAlias),
 }
-// FIXME: not every function, ... is actually an assoc item. maybe we should make
-// sure that you can only turn actual assoc items into AssocItems. This would
-// require not implementing From, and instead having some checked way of
-// casting them, and somehow making the constructors private, which would be annoying.
-impl_froms!(AssocItem: Function, Const, TypeAlias);
+pub enum AssocItemContainer {
+    Trait(Trait),
+    ImplBlock(ImplBlock),
+}
+pub trait AsAssocItem {
+    fn as_assoc_item(self, db: &impl DefDatabase) -> Option<AssocItem>;
+}
+
+impl AsAssocItem for Function {
+    fn as_assoc_item(self, db: &impl DefDatabase) -> Option<AssocItem> {
+        as_assoc_item(db, AssocItem::Function, self.id)
+    }
+}
+impl AsAssocItem for Const {
+    fn as_assoc_item(self, db: &impl DefDatabase) -> Option<AssocItem> {
+        as_assoc_item(db, AssocItem::Const, self.id)
+    }
+}
+impl AsAssocItem for TypeAlias {
+    fn as_assoc_item(self, db: &impl DefDatabase) -> Option<AssocItem> {
+        as_assoc_item(db, AssocItem::TypeAlias, self.id)
+    }
+}
+fn as_assoc_item<ID, DEF, CTOR, AST>(db: &impl DefDatabase, ctor: CTOR, id: ID) -> Option<AssocItem>
+where
+    ID: Lookup<Data = AssocItemLoc<AST>>,
+    DEF: From<ID>,
+    CTOR: FnOnce(DEF) -> AssocItem,
+    AST: AstNode,
+{
+    match id.lookup(db).container {
+        AssocContainerId::TraitId(_) | AssocContainerId::ImplId(_) => Some(ctor(DEF::from(id))),
+        AssocContainerId::ContainerId(_) => None,
+    }
+}
 
 impl AssocItem {
     pub fn module(self, db: &impl DefDatabase) -> Module {
@@ -659,6 +696,18 @@ impl AssocItem {
             AssocItem::TypeAlias(t) => t.module(db),
         }
     }
+    pub fn container(self, db: &impl DefDatabase) -> AssocItemContainer {
+        let container = match self {
+            AssocItem::Function(it) => it.id.lookup(db).container,
+            AssocItem::Const(it) => it.id.lookup(db).container,
+            AssocItem::TypeAlias(it) => it.id.lookup(db).container,
+        };
+        match container {
+            AssocContainerId::TraitId(id) => AssocItemContainer::Trait(id.into()),
+            AssocContainerId::ImplId(id) => AssocItemContainer::ImplBlock(id.into()),
+            AssocContainerId::ContainerId(_) => panic!("invalid AssocItem"),
+        }
+    }
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
@@ -769,6 +818,7 @@ impl TypeParam {
     }
 }
 
+// FIXME: rename from `ImplBlock` to `Impl`
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ImplBlock {
     pub(crate) id: ImplId,
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index e1c7b7a20..5cd965f7a 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -39,10 +39,10 @@ mod has_source;
 
 pub use crate::{
     code_model::{
-        Adt, AssocItem, AttrDef, Const, Crate, CrateDependency, DefWithBody, Docs, Enum,
-        EnumVariant, FieldSource, Function, GenericDef, HasAttrs, HasVisibility, ImplBlock, Local,
-        MacroDef, Module, ModuleDef, ScopeDef, Static, Struct, StructField, Trait, Type, TypeAlias,
-        TypeParam, Union, VariantDef,
+        Adt, AsAssocItem, AssocItem, AssocItemContainer, AttrDef, Const, Crate, CrateDependency,
+        DefWithBody, Docs, Enum, EnumVariant, FieldSource, Function, GenericDef, HasAttrs,
+        HasVisibility, ImplBlock, Local, MacroDef, Module, ModuleDef, ScopeDef, Static, Struct,
+        StructField, Trait, Type, TypeAlias, TypeParam, Union, VariantDef,
     },
     has_source::HasSource,
     source_analyzer::{PathResolution, ScopeEntryWithSyntax, SourceAnalyzer},
diff --git a/crates/ra_hir_expand/src/lib.rs b/crates/ra_hir_expand/src/lib.rs
index 7cf3b59a7..9506f2e1c 100644
--- a/crates/ra_hir_expand/src/lib.rs
+++ b/crates/ra_hir_expand/src/lib.rs
@@ -323,11 +323,18 @@ impl<T: Clone> InFile<&T> {
     }
 }
 
+impl<T> InFile<Option<T>> {
+    pub fn transpose(self) -> Option<InFile<T>> {
+        let value = self.value?;
+        Some(InFile::new(self.file_id, value))
+    }
+}
+
 impl InFile<SyntaxNode> {
-    pub fn ancestors_with_macros<'a>(
+    pub fn ancestors_with_macros(
         self,
-        db: &'a impl crate::db::AstDatabase,
-    ) -> impl Iterator<Item = InFile<SyntaxNode>> + 'a {
+        db: &impl crate::db::AstDatabase,
+    ) -> impl Iterator<Item = InFile<SyntaxNode>> + '_ {
         std::iter::successors(Some(self), move |node| match node.value.parent() {
             Some(parent) => Some(node.with_value(parent)),
             None => {
@@ -338,6 +345,15 @@ impl InFile<SyntaxNode> {
     }
 }
 
+impl InFile<SyntaxToken> {
+    pub fn ancestors_with_macros(
+        self,
+        db: &impl crate::db::AstDatabase,
+    ) -> impl Iterator<Item = InFile<SyntaxNode>> + '_ {
+        self.map(|it| it.parent()).ancestors_with_macros(db)
+    }
+}
+
 impl<N: AstNode> InFile<N> {
     pub fn descendants<T: AstNode>(self) -> impl Iterator<Item = InFile<T>> {
         self.value.syntax().descendants().filter_map(T::cast).map(move |n| self.with_value(n))
diff --git a/crates/ra_ide/src/goto_type_definition.rs b/crates/ra_ide/src/goto_type_definition.rs
index 11ad6d137..69940fc36 100644
--- a/crates/ra_ide/src/goto_type_definition.rs
+++ b/crates/ra_ide/src/goto_type_definition.rs
@@ -16,24 +16,16 @@ pub(crate) fn goto_type_definition(
     let token = pick_best(file.token_at_offset(position.offset))?;
     let token = descend_into_macros(db, position.file_id, token);
 
-    let node = token.value.ancestors().find_map(|token| {
-        token
-            .ancestors()
-            .find(|n| ast::Expr::cast(n.clone()).is_some() || ast::Pat::cast(n.clone()).is_some())
-    })?;
+    let node = token
+        .value
+        .ancestors()
+        .find(|n| ast::Expr::cast(n.clone()).is_some() || ast::Pat::cast(n.clone()).is_some())?;
 
     let analyzer = hir::SourceAnalyzer::new(db, token.with_value(&node), None);
 
-    let ty: hir::Type = if let Some(ty) =
-        ast::Expr::cast(node.clone()).and_then(|e| analyzer.type_of(db, &e))
-    {
-        ty
-    } else if let Some(ty) = ast::Pat::cast(node.clone()).and_then(|p| analyzer.type_of_pat(db, &p))
-    {
-        ty
-    } else {
-        return None;
-    };
+    let ty: hir::Type = ast::Expr::cast(node.clone())
+        .and_then(|e| analyzer.type_of(db, &e))
+        .or_else(|| ast::Pat::cast(node.clone()).and_then(|p| analyzer.type_of_pat(db, &p)))?;
 
     let adt_def = ty.autoderef(db).find_map(|ty| ty.as_adt())?;
 
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 59c86bbfa..2e598fdcd 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -758,7 +758,7 @@ pub fn handle_code_lens(
     // Gather runnables
     for runnable in world.analysis().runnables(file_id)? {
         let title = match &runnable.kind {
-            RunnableKind::Test { .. } | RunnableKind::TestMod { .. } => "▶️Run Test",
+            RunnableKind::Test { .. } | RunnableKind::TestMod { .. } => "▶️\u{fe0e}Run Test",
             RunnableKind::Bench { .. } => "Run Bench",
             RunnableKind::Bin => "Run",
         }
diff --git a/crates/ra_parser/src/grammar/params.rs b/crates/ra_parser/src/grammar/params.rs
index ed4f93347..272661b1d 100644
--- a/crates/ra_parser/src/grammar/params.rs
+++ b/crates/ra_parser/src/grammar/params.rs
@@ -114,8 +114,11 @@ fn value_parameter(p: &mut Parser, flavor: Flavor) {
         // test fn_pointer_param_ident_path
         // type Foo = fn(Bar::Baz);
         // type Qux = fn(baz: Bar::Baz);
+
+        // test fn_pointer_unnamed_arg
+        // type Foo = fn(_: bar);
         Flavor::FnPointer => {
-            if p.at(IDENT) && p.nth(1) == T![:] && !p.nth_at(1, T![::]) {
+            if (p.at(IDENT) || p.at(UNDERSCORE)) && p.nth(1) == T![:] && !p.nth_at(1, T![::]) {
                 patterns::pattern_single(p);
                 types::ascription(p);
             } else {
diff --git a/crates/ra_project_model/Cargo.toml b/crates/ra_project_model/Cargo.toml
index 69edc3c66..653d5bd14 100644
--- a/crates/ra_project_model/Cargo.toml
+++ b/crates/ra_project_model/Cargo.toml
@@ -19,3 +19,5 @@ ra_cfg = { path = "../ra_cfg" }
 
 serde = { version = "1.0.89", features = ["derive"] }
 serde_json = "1.0.39"
+
+anyhow = "1.0.26"
diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index 60cb8c1eb..22d226a74 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -2,14 +2,13 @@
 
 use std::path::{Path, PathBuf};
 
+use anyhow::{Context, Result};
 use cargo_metadata::{CargoOpt, MetadataCommand};
 use ra_arena::{impl_arena_id, Arena, RawId};
 use ra_db::Edition;
 use rustc_hash::FxHashMap;
 use serde::Deserialize;
 
-use crate::Result;
-
 /// `CargoWorkspace` represents the logical structure of, well, a Cargo
 /// workspace. It pretty closely mirrors `cargo metadata` output.
 ///
@@ -171,7 +170,9 @@ impl CargoWorkspace {
         if let Some(parent) = cargo_toml.parent() {
             meta.current_dir(parent);
         }
-        let meta = meta.exec().map_err(|e| format!("cargo metadata failed: {}", e))?;
+        let meta = meta.exec().with_context(|| {
+            format!("Failed to run `cargo metadata --manifest-path {}`", cargo_toml.display())
+        })?;
         let mut pkg_by_id = FxHashMap::default();
         let mut packages = Arena::default();
         let mut targets = Arena::default();
@@ -181,7 +182,9 @@ impl CargoWorkspace {
         for meta_pkg in meta.packages {
             let cargo_metadata::Package { id, edition, name, manifest_path, .. } = meta_pkg;
             let is_member = ws_members.contains(&id);
-            let edition = edition.parse::<Edition>()?;
+            let edition = edition
+                .parse::<Edition>()
+                .with_context(|| format!("Failed to parse edition {}", edition))?;
             let pkg = packages.alloc(PackageData {
                 name,
                 manifest: manifest_path,
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index bc1d15406..fef405b7f 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -12,6 +12,7 @@ use std::{
     process::Command,
 };
 
+use anyhow::{bail, Context, Result};
 use ra_cfg::CfgOptions;
 use ra_db::{CrateGraph, CrateId, CrateName, Edition, Env, FileId};
 use rustc_hash::FxHashMap;
@@ -23,8 +24,6 @@ pub use crate::{
     sysroot::Sysroot,
 };
 
-pub type Result<T> = ::std::result::Result<T, Box<dyn Error + Send + Sync>>;
-
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub struct CargoTomlNotFoundError(pub PathBuf);
 
@@ -81,15 +80,36 @@ impl ProjectWorkspace {
     ) -> Result<ProjectWorkspace> {
         match find_rust_project_json(path) {
             Some(json_path) => {
-                let file = File::open(json_path)?;
+                let file = File::open(&json_path)
+                    .with_context(|| format!("Failed to open json file {}", json_path.display()))?;
                 let reader = BufReader::new(file);
-                Ok(ProjectWorkspace::Json { project: from_reader(reader)? })
+                Ok(ProjectWorkspace::Json {
+                    project: from_reader(reader).with_context(|| {
+                        format!("Failed to deserialize json file {}", json_path.display())
+                    })?,
+                })
             }
             None => {
-                let cargo_toml = find_cargo_toml(path)?;
-                let cargo = CargoWorkspace::from_cargo_metadata(&cargo_toml, cargo_features)?;
-                let sysroot =
-                    if with_sysroot { Sysroot::discover(&cargo_toml)? } else { Sysroot::default() };
+                let cargo_toml = find_cargo_toml(path).with_context(|| {
+                    format!("Failed to find Cargo.toml for path {}", path.display())
+                })?;
+                let cargo = CargoWorkspace::from_cargo_metadata(&cargo_toml, cargo_features)
+                    .with_context(|| {
+                        format!(
+                            "Failed to read Cargo metadata from Cargo.toml file {}",
+                            cargo_toml.display()
+                        )
+                    })?;
+                let sysroot = if with_sysroot {
+                    Sysroot::discover(&cargo_toml).with_context(|| {
+                        format!(
+                            "Failed to find sysroot for Cargo.toml file {}",
+                            cargo_toml.display()
+                        )
+                    })?
+                } else {
+                    Sysroot::default()
+                };
                 Ok(ProjectWorkspace::Cargo { cargo, sysroot })
             }
         }
@@ -403,11 +423,20 @@ pub fn get_rustc_cfg_options() -> CfgOptions {
         }
     }
 
-    match (|| -> Result<_> {
+    match (|| -> Result<String> {
         // `cfg(test)` and `cfg(debug_assertion)` are handled outside, so we suppress them here.
-        let output = Command::new("rustc").args(&["--print", "cfg", "-O"]).output()?;
+        let output = Command::new("rustc")
+            .args(&["--print", "cfg", "-O"])
+            .output()
+            .context("Failed to get output from rustc --print cfg -O")?;
         if !output.status.success() {
-            Err("failed to get rustc cfgs")?;
+            bail!(
+                "rustc --print cfg -O exited with exit code ({})",
+                output
+                    .status
+                    .code()
+                    .map_or(String::from("no exit code"), |code| format!("{}", code))
+            );
         }
         Ok(String::from_utf8(output.stdout)?)
     })() {
diff --git a/crates/ra_project_model/src/sysroot.rs b/crates/ra_project_model/src/sysroot.rs
index a23265fc0..7b9cc899c 100644
--- a/crates/ra_project_model/src/sysroot.rs
+++ b/crates/ra_project_model/src/sysroot.rs
@@ -1,5 +1,6 @@
 //! FIXME: write short doc here
 
+use anyhow::{anyhow, bail, Context, Result};
 use std::{
     env,
     path::{Path, PathBuf},
@@ -8,8 +9,6 @@ use std::{
 
 use ra_arena::{impl_arena_id, Arena, RawId};
 
-use crate::Result;
-
 #[derive(Default, Debug, Clone)]
 pub struct Sysroot {
     crates: Arena<SysrootCrate, SysrootCrateData>,
@@ -51,7 +50,7 @@ impl Sysroot {
         let src = try_find_src_path(cargo_toml)?;
 
         if !src.exists() {
-            Err(format!(
+            Err(anyhow!(
                 "can't load standard library from sysroot\n\
                  {}\n\
                  (discovered via `rustc --print sysroot`)\n\
@@ -100,9 +99,14 @@ fn try_find_src_path(cargo_toml: &Path) -> Result<PathBuf> {
         .current_dir(cargo_toml.parent().unwrap())
         .args(&["--print", "sysroot"])
         .output()
-        .map_err(|e| format!("rustc --print sysroot failed: {}", e))?;
+        .context("rustc --print sysroot failed")?;
     if !rustc_output.status.success() {
-        Err("failed to locate sysroot")?;
+        match rustc_output.status.code() {
+            Some(code) => {
+                bail!("failed to locate sysroot: rustc --print sysroot exited with code {}", code)
+            }
+            None => bail!("failed to locate sysroot: rustc --print sysroot terminated by signal"),
+        };
     }
     let stdout = String::from_utf8(rustc_output.stdout)?;
     let sysroot_path = Path::new(stdout.trim());
diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index d3e8888bd..9cc7930f7 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -18,8 +18,8 @@ use crate::{
 pub use self::{
     expr_extensions::{ArrayExprKind, BinOp, ElseBranch, LiteralKind, PrefixOp, RangeOp},
     extensions::{
-        FieldKind, PathSegmentKind, SelfParamKind, SlicePatComponents, StructKind, TypeBoundKind,
-        VisibilityKind,
+        AttrKind, FieldKind, PathSegmentKind, SelfParamKind, SlicePatComponents, StructKind,
+        TypeBoundKind, VisibilityKind,
     },
     generated::*,
     tokens::*,
@@ -217,10 +217,7 @@ fn test_doc_comment_multi_line_block_strips_suffix() {
 #[test]
 fn test_comments_preserve_trailing_whitespace() {
     let file = SourceFile::parse(
-        r#"
-/// Representation of a Realm.   
-/// In the specification these are called Realm Records.
-struct Realm {}"#,
+        "\n/// Representation of a Realm.   \n/// In the specification these are called Realm Records.\nstruct Realm {}",
     )
     .ok()
     .unwrap();
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index 7dcf084de..44de4af89 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -37,6 +37,12 @@ fn text_of_first_token(node: &SyntaxNode) -> &SmolStr {
     node.green().children().next().and_then(|it| it.into_token()).unwrap().text()
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AttrKind {
+    Inner,
+    Outer,
+}
+
 impl ast::Attr {
     pub fn as_simple_atom(&self) -> Option<SmolStr> {
         match self.input() {
@@ -71,6 +77,18 @@ impl ast::Attr {
             _ => None,
         }
     }
+
+    pub fn kind(&self) -> AttrKind {
+        let first_token = self.syntax().first_token();
+        let first_token_kind = first_token.as_ref().map(SyntaxToken::kind);
+        let second_token_kind =
+            first_token.and_then(|token| token.next_token()).as_ref().map(SyntaxToken::kind);
+
+        match (first_token_kind, second_token_kind) {
+            (Some(SyntaxKind::POUND), Some(SyntaxKind::EXCL)) => AttrKind::Inner,
+            _ => AttrKind::Outer,
+        }
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
diff --git a/crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.rs b/crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.rs
new file mode 100644
index 000000000..1ebbe5b03
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.rs
@@ -0,0 +1 @@
+type Foo = fn(_: bar);
diff --git a/crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.txt b/crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.txt
new file mode 100644
index 000000000..52d8f21a4
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.txt
@@ -0,0 +1,26 @@
+SOURCE_FILE@[0; 23)
+  TYPE_ALIAS_DEF@[0; 22)
+    TYPE_KW@[0; 4) "type"
+    WHITESPACE@[4; 5) " "
+    NAME@[5; 8)
+      IDENT@[5; 8) "Foo"
+    WHITESPACE@[8; 9) " "
+    EQ@[9; 10) "="
+    WHITESPACE@[10; 11) " "
+    FN_POINTER_TYPE@[11; 21)
+      FN_KW@[11; 13) "fn"
+      PARAM_LIST@[13; 21)
+        L_PAREN@[13; 14) "("
+        PARAM@[14; 20)
+          PLACEHOLDER_PAT@[14; 15)
+            UNDERSCORE@[14; 15) "_"
+          COLON@[15; 16) ":"
+          WHITESPACE@[16; 17) " "
+          PATH_TYPE@[17; 20)
+            PATH@[17; 20)
+              PATH_SEGMENT@[17; 20)
+                NAME_REF@[17; 20)
+                  IDENT@[17; 20) "bar"
+        R_PAREN@[20; 21) ")"
+    SEMI@[21; 22) ";"
+  WHITESPACE@[22; 23) "\n"