7 files changed, 801 insertions, 98 deletions

diff --git a/crates/ra_ide/src/completion/complete_attribute.rs b/crates/ra_ide/src/completion/complete_attribute.rs
index 8bf952798..f17266221 100644
--- a/crates/ra_ide/src/completion/complete_attribute.rs
+++ b/crates/ra_ide/src/completion/complete_attribute.rs
@@ -3,25 +3,29 @@
 //! This module uses a bit of static metadata to provide completions
 //! for built-in attributes.
 
-use super::completion_context::CompletionContext;
-use super::completion_item::{CompletionItem, CompletionItemKind, CompletionKind, Completions};
-use ra_syntax::{
-    ast::{Attr, AttrKind},
-    AstNode,
+use ra_syntax::{ast, AstNode, SyntaxKind};
+use rustc_hash::FxHashSet;
+
+use crate::completion::{
+    completion_context::CompletionContext,
+    completion_item::{CompletionItem, CompletionItemKind, CompletionKind, Completions},
 };
 
-pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) {
-    if !ctx.is_attribute {
-        return;
-    }
+pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
+    let attribute = ctx.attribute_under_caret.as_ref()?;
 
-    let is_inner = ctx
-        .original_token
-        .ancestors()
-        .find_map(Attr::cast)
-        .map(|attr| attr.kind() == AttrKind::Inner)
-        .unwrap_or(false);
+    match (attribute.path(), attribute.input()) {
+        (Some(path), Some(ast::AttrInput::TokenTree(token_tree)))
+            if path.to_string() == "derive" =>
+        {
+            complete_derive(acc, ctx, token_tree)
+        }
+        _ => complete_attribute_start(acc, ctx, attribute),
+    }
+    Some(())
+}
 
+fn complete_attribute_start(acc: &mut Completions, ctx: &CompletionContext, attribute: &ast::Attr) {
     for attr_completion in ATTRIBUTES {
         let mut item = CompletionItem::new(
             CompletionKind::Attribute,
@@ -37,7 +41,7 @@ pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext)
             _ => {}
         }
 
-        if is_inner || !attr_completion.should_be_inner {
+        if attribute.kind() == ast::AttrKind::Inner || !attr_completion.should_be_inner {
             acc.add(item);
         }
     }
@@ -126,6 +130,106 @@ const ATTRIBUTES: &[AttrCompletion] = &[
     },
 ];
 
+fn complete_derive(acc: &mut Completions, ctx: &CompletionContext, derive_input: ast::TokenTree) {
+    if let Ok(existing_derives) = parse_derive_input(derive_input) {
+        for derive_completion in DEFAULT_DERIVE_COMPLETIONS
+            .into_iter()
+            .filter(|completion| !existing_derives.contains(completion.label))
+        {
+            let mut label = derive_completion.label.to_owned();
+            for dependency in derive_completion
+                .dependencies
+                .into_iter()
+                .filter(|&&dependency| !existing_derives.contains(dependency))
+            {
+                label.push_str(", ");
+                label.push_str(dependency);
+            }
+            acc.add(
+                CompletionItem::new(CompletionKind::Attribute, ctx.source_range(), label)
+                    .kind(CompletionItemKind::Attribute),
+            );
+        }
+
+        for custom_derive_name in get_derive_names_in_scope(ctx).difference(&existing_derives) {
+            acc.add(
+                CompletionItem::new(
+                    CompletionKind::Attribute,
+                    ctx.source_range(),
+                    custom_derive_name,
+                )
+                .kind(CompletionItemKind::Attribute),
+            );
+        }
+    }
+}
+
+fn parse_derive_input(derive_input: ast::TokenTree) -> Result<FxHashSet<String>, ()> {
+    match (derive_input.left_delimiter_token(), derive_input.right_delimiter_token()) {
+        (Some(left_paren), Some(right_paren))
+            if left_paren.kind() == SyntaxKind::L_PAREN
+                && right_paren.kind() == SyntaxKind::R_PAREN =>
+        {
+            let mut input_derives = FxHashSet::default();
+            let mut current_derive = String::new();
+            for token in derive_input
+                .syntax()
+                .children_with_tokens()
+                .filter_map(|token| token.into_token())
+                .skip_while(|token| token != &left_paren)
+                .skip(1)
+                .take_while(|token| token != &right_paren)
+            {
+                if SyntaxKind::COMMA == token.kind() {
+                    if !current_derive.is_empty() {
+                        input_derives.insert(current_derive);
+                        current_derive = String::new();
+                    }
+                } else {
+                    current_derive.push_str(token.to_string().trim());
+                }
+            }
+
+            if !current_derive.is_empty() {
+                input_derives.insert(current_derive);
+            }
+            Ok(input_derives)
+        }
+        _ => Err(()),
+    }
+}
+
+fn get_derive_names_in_scope(ctx: &CompletionContext) -> FxHashSet<String> {
+    let mut result = FxHashSet::default();
+    ctx.scope().process_all_names(&mut |name, scope_def| {
+        if let hir::ScopeDef::MacroDef(mac) = scope_def {
+            if mac.is_derive_macro() {
+                result.insert(name.to_string());
+            }
+        }
+    });
+    result
+}
+
+struct DeriveCompletion {
+    label: &'static str,
+    dependencies: &'static [&'static str],
+}
+
+/// Standard Rust derives and the information about their dependencies
+/// (the dependencies are needed so that the main derive don't break the compilation when added)
+const DEFAULT_DERIVE_COMPLETIONS: &[DeriveCompletion] = &[
+    DeriveCompletion { label: "Clone", dependencies: &[] },
+    DeriveCompletion { label: "Copy", dependencies: &["Clone"] },
+    DeriveCompletion { label: "Debug", dependencies: &[] },
+    DeriveCompletion { label: "Default", dependencies: &[] },
+    DeriveCompletion { label: "Hash", dependencies: &[] },
+    DeriveCompletion { label: "PartialEq", dependencies: &[] },
+    DeriveCompletion { label: "Eq", dependencies: &["PartialEq"] },
+    DeriveCompletion { label: "PartialOrd", dependencies: &["PartialEq"] },
+    DeriveCompletion { label: "Ord", dependencies: &["PartialOrd", "Eq", "PartialEq"] },
+];
+
 #[cfg(test)]
 mod tests {
     use crate::completion::{test_utils::do_completion, CompletionItem, CompletionKind};
@@ -136,6 +240,170 @@ mod tests {
     }
 
     #[test]
+    fn empty_derive_completion() {
+        assert_debug_snapshot!(
+            do_attr_completion(
+                    r"
+                    #[derive(<|>)]
+                    struct Test {}
+                    ",
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "Clone",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Copy, Clone",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Copy, Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Debug",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Debug",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Default",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Default",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Eq, PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Eq, PartialEq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Hash",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Hash",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Ord, PartialOrd, Eq, PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "Ord, PartialOrd, Eq, PartialEq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "PartialEq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "PartialOrd, PartialEq",
+                source_range: 30..30,
+                delete: 30..30,
+                insert: "PartialOrd, PartialEq",
+                kind: Attribute,
+            },
+        ]
+            "###
+        );
+    }
+
+    #[test]
+    fn no_completion_for_incorrect_derive() {
+        assert_debug_snapshot!(
+            do_attr_completion(
+                r"
+                    #[derive{<|>)]
+                    struct Test {}
+                    ",
+            ),
+            @"[]"
+        );
+    }
+
+    #[test]
+    fn derive_with_input_completion() {
+        assert_debug_snapshot!(
+            do_attr_completion(
+                    r"
+                    #[derive(serde::Serialize, PartialEq, <|>)]
+                    struct Test {}
+                    ",
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "Clone",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Copy, Clone",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Copy, Clone",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Debug",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Debug",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Default",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Default",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Eq",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Eq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Hash",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Hash",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "Ord, PartialOrd, Eq",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "Ord, PartialOrd, Eq",
+                kind: Attribute,
+            },
+            CompletionItem {
+                label: "PartialOrd",
+                source_range: 59..59,
+                delete: 59..59,
+                insert: "PartialOrd",
+                kind: Attribute,
+            },
+        ]
+            "###
+        );
+    }
+
+    #[test]
     fn test_attribute_completion() {
         assert_debug_snapshot!(
         do_attr_completion(
diff --git a/crates/ra_ide/src/completion/complete_dot.rs b/crates/ra_ide/src/completion/complete_dot.rs
index 814354ffa..05f825c6f 100644
--- a/crates/ra_ide/src/completion/complete_dot.rs
+++ b/crates/ra_ide/src/completion/complete_dot.rs
@@ -250,6 +250,44 @@ mod tests {
     }
 
     #[test]
+    fn test_union_field_completion() {
+        assert_debug_snapshot!(
+            do_ref_completion(
+                r"
+            union Un {
+                field: u8,
+                other: u16,
+            }
+
+            fn foo(u: Un) {
+                u.<|>
+            }
+            ",
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "field",
+                source_range: 140..140,
+                delete: 140..140,
+                insert: "field",
+                kind: Field,
+                detail: "u8",
+            },
+            CompletionItem {
+                label: "other",
+                source_range: 140..140,
+                delete: 140..140,
+                insert: "other",
+                kind: Field,
+                detail: "u16",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
     fn test_method_completion() {
         assert_debug_snapshot!(
         do_ref_completion(
diff --git a/crates/ra_ide/src/completion/complete_qualified_path.rs b/crates/ra_ide/src/completion/complete_qualified_path.rs
index dd10f74e6..7fcd22525 100644
--- a/crates/ra_ide/src/completion/complete_qualified_path.rs
+++ b/crates/ra_ide/src/completion/complete_qualified_path.rs
@@ -2,6 +2,7 @@
 
 use hir::{Adt, HasVisibility, PathResolution, ScopeDef};
 use ra_syntax::AstNode;
+use rustc_hash::FxHashSet;
 use test_utils::tested_by;
 
 use crate::completion::{CompletionContext, Completions};
@@ -9,15 +10,29 @@ use crate::completion::{CompletionContext, Completions};
 pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionContext) {
     let path = match &ctx.path_prefix {
         Some(path) => path.clone(),
-        _ => return,
+        None => return,
     };
-    let def = match ctx.scope().resolve_hir_path(&path) {
-        Some(PathResolution::Def(def)) => def,
-        _ => return,
+
+    if ctx.attribute_under_caret.is_some() {
+        return;
+    }
+
+    let scope = ctx.scope();
+    let context_module = scope.module();
+
+    let res = match scope.resolve_hir_path(&path) {
+        Some(res) => res,
+        None => return,
     };
-    let context_module = ctx.scope().module();
-    match def {
-        hir::ModuleDef::Module(module) => {
+
+    // Add associated types on type parameters and `Self`.
+    res.assoc_type_shorthand_candidates(ctx.db, |alias| {
+        acc.add_type_alias(ctx, alias);
+        None::<()>
+    });
+
+    match res {
+        PathResolution::Def(hir::ModuleDef::Module(module)) => {
             let module_scope = module.scope(ctx.db, context_module);
             for (name, def) in module_scope {
                 if ctx.use_item_syntax.is_some() {
@@ -35,7 +50,8 @@ pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
                 acc.add_resolution(ctx, name.to_string(), &def);
             }
         }
-        hir::ModuleDef::Adt(_) | hir::ModuleDef::TypeAlias(_) => {
+        PathResolution::Def(def @ hir::ModuleDef::Adt(_))
+        | PathResolution::Def(def @ hir::ModuleDef::TypeAlias(_)) => {
             if let hir::ModuleDef::Adt(Adt::Enum(e)) = def {
                 for variant in e.variants(ctx.db) {
                     acc.add_enum_variant(ctx, variant, None);
@@ -46,8 +62,10 @@ pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
                 hir::ModuleDef::TypeAlias(a) => a.ty(ctx.db),
                 _ => unreachable!(),
             };
-            // Iterate assoc types separately
-            // FIXME: complete T::AssocType
+
+            // XXX: For parity with Rust bug #22519, this does not complete Ty::AssocType.
+            // (where AssocType is defined on a trait, not an inherent impl)
+
             let krate = ctx.krate;
             if let Some(krate) = krate {
                 let traits_in_scope = ctx.scope().traits_in_scope();
@@ -65,7 +83,8 @@ pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
                     None::<()>
                 });
 
-                ty.iterate_impl_items(ctx.db, krate, |item| {
+                // Iterate assoc types separately
+                ty.iterate_assoc_items(ctx.db, krate, |item| {
                     if context_module.map_or(false, |m| !item.is_visible_from(ctx.db, m)) {
                         return None;
                     }
@@ -77,7 +96,8 @@ pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
                 });
             }
         }
-        hir::ModuleDef::Trait(t) => {
+        PathResolution::Def(hir::ModuleDef::Trait(t)) => {
+            // Handles `Trait::assoc` as well as `<Ty as Trait>::assoc`.
             for item in t.items(ctx.db) {
                 if context_module.map_or(false, |m| !item.is_visible_from(ctx.db, m)) {
                     continue;
@@ -91,8 +111,38 @@ pub(super) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
                 }
             }
         }
+        PathResolution::TypeParam(_) | PathResolution::SelfType(_) => {
+            if let Some(krate) = ctx.krate {
+                let ty = match res {
+                    PathResolution::TypeParam(param) => param.ty(ctx.db),
+                    PathResolution::SelfType(impl_def) => impl_def.target_ty(ctx.db),
+                    _ => return,
+                };
+
+                let traits_in_scope = ctx.scope().traits_in_scope();
+                let mut seen = FxHashSet::default();
+                ty.iterate_path_candidates(ctx.db, krate, &traits_in_scope, None, |_ty, item| {
+                    if context_module.map_or(false, |m| !item.is_visible_from(ctx.db, m)) {
+                        return None;
+                    }
+
+                    // We might iterate candidates of a trait multiple times here, so deduplicate
+                    // them.
+                    if seen.insert(item) {
+                        match item {
+                            hir::AssocItem::Function(func) => {
+                                acc.add_function(ctx, func, None);
+                            }
+                            hir::AssocItem::Const(ct) => acc.add_const(ctx, ct),
+                            hir::AssocItem::TypeAlias(ty) => acc.add_type_alias(ctx, ty),
+                        }
+                    }
+                    None::<()>
+                });
+            }
+        }
         _ => {}
-    };
+    }
 }
 
 #[cfg(test)]
@@ -844,6 +894,211 @@ mod tests {
     }
 
     #[test]
+    fn completes_ty_param_assoc_ty() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                "
+                //- /lib.rs
+                trait Super {
+                    type Ty;
+                    const CONST: u8;
+                    fn func() {}
+                    fn method(&self) {}
+                }
+
+                trait Sub: Super {
+                    type SubTy;
+                    const C2: ();
+                    fn subfunc() {}
+                    fn submethod(&self) {}
+                }
+
+                fn foo<T: Sub>() {
+                    T::<|>
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "C2",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "C2",
+                kind: Const,
+                detail: "const C2: ();",
+            },
+            CompletionItem {
+                label: "CONST",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "CONST",
+                kind: Const,
+                detail: "const CONST: u8;",
+            },
+            CompletionItem {
+                label: "SubTy",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "SubTy",
+                kind: TypeAlias,
+                detail: "type SubTy;",
+            },
+            CompletionItem {
+                label: "Ty",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "Ty",
+                kind: TypeAlias,
+                detail: "type Ty;",
+            },
+            CompletionItem {
+                label: "func()",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "func()$0",
+                kind: Function,
+                lookup: "func",
+                detail: "fn func()",
+            },
+            CompletionItem {
+                label: "method()",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "method()$0",
+                kind: Method,
+                lookup: "method",
+                detail: "fn method(&self)",
+            },
+            CompletionItem {
+                label: "subfunc()",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "subfunc()$0",
+                kind: Function,
+                lookup: "subfunc",
+                detail: "fn subfunc()",
+            },
+            CompletionItem {
+                label: "submethod()",
+                source_range: 219..219,
+                delete: 219..219,
+                insert: "submethod()$0",
+                kind: Method,
+                lookup: "submethod",
+                detail: "fn submethod(&self)",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
+    fn completes_self_param_assoc_ty() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                "
+                //- /lib.rs
+                trait Super {
+                    type Ty;
+                    const CONST: u8 = 0;
+                    fn func() {}
+                    fn method(&self) {}
+                }
+
+                trait Sub: Super {
+                    type SubTy;
+                    const C2: () = ();
+                    fn subfunc() {}
+                    fn submethod(&self) {}
+                }
+
+                struct Wrap<T>(T);
+                impl<T> Super for Wrap<T> {}
+                impl<T> Sub for Wrap<T> {
+                    fn subfunc() {
+                        // Should be able to assume `Self: Sub + Super`
+                        Self::<|>
+                    }
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "C2",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "C2",
+                kind: Const,
+                detail: "const C2: () = ();",
+            },
+            CompletionItem {
+                label: "CONST",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "CONST",
+                kind: Const,
+                detail: "const CONST: u8 = 0;",
+            },
+            CompletionItem {
+                label: "SubTy",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "SubTy",
+                kind: TypeAlias,
+                detail: "type SubTy;",
+            },
+            CompletionItem {
+                label: "Ty",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "Ty",
+                kind: TypeAlias,
+                detail: "type Ty;",
+            },
+            CompletionItem {
+                label: "func()",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "func()$0",
+                kind: Function,
+                lookup: "func",
+                detail: "fn func()",
+            },
+            CompletionItem {
+                label: "method()",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "method()$0",
+                kind: Method,
+                lookup: "method",
+                detail: "fn method(&self)",
+            },
+            CompletionItem {
+                label: "subfunc()",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "subfunc()$0",
+                kind: Function,
+                lookup: "subfunc",
+                detail: "fn subfunc()",
+            },
+            CompletionItem {
+                label: "submethod()",
+                source_range: 365..365,
+                delete: 365..365,
+                insert: "submethod()$0",
+                kind: Method,
+                lookup: "submethod",
+                detail: "fn submethod(&self)",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
     fn completes_type_alias() {
         assert_debug_snapshot!(
             do_reference_completion(
@@ -1075,4 +1330,18 @@ mod tests {
         "###
         );
     }
+
+    #[test]
+    fn dont_complete_attr() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                mod foo { pub struct Foo; }
+                #[foo::<|>]
+                fn f() {}
+                "
+            ),
+            @r###"[]"###
+        )
+    }
 }
diff --git a/crates/ra_ide/src/completion/complete_trait_impl.rs b/crates/ra_ide/src/completion/complete_trait_impl.rs
index ee32d1ff6..039df03e0 100644
--- a/crates/ra_ide/src/completion/complete_trait_impl.rs
+++ b/crates/ra_ide/src/completion/complete_trait_impl.rs
@@ -32,7 +32,7 @@
 //! ```
 
 use hir::{self, Docs, HasSource};
-use ra_assists::utils::get_missing_impl_items;
+use ra_assists::utils::get_missing_assoc_items;
 use ra_syntax::{
     ast::{self, edit, ImplDef},
     AstNode, SyntaxKind, SyntaxNode, TextRange, T,
@@ -50,7 +50,7 @@ pub(crate) fn complete_trait_impl(acc: &mut Completions, ctx: &CompletionContext
     if let Some((trigger, impl_def)) = completion_match(ctx) {
         match trigger.kind() {
             SyntaxKind::NAME_REF => {
-                get_missing_impl_items(&ctx.sema, &impl_def).iter().for_each(|item| match item {
+                get_missing_assoc_items(&ctx.sema, &impl_def).iter().for_each(|item| match item {
                     hir::AssocItem::Function(fn_item) => {
                         add_function_impl(&trigger, acc, ctx, &fn_item)
                     }
@@ -64,34 +64,40 @@ pub(crate) fn complete_trait_impl(acc: &mut Completions, ctx: &CompletionContext
             }
 
             SyntaxKind::FN_DEF => {
-                for missing_fn in get_missing_impl_items(&ctx.sema, &impl_def).iter().filter_map(
-                    |item| match item {
-                        hir::AssocItem::Function(fn_item) => Some(fn_item),
-                        _ => None,
-                    },
-                ) {
+                for missing_fn in
+                    get_missing_assoc_items(&ctx.sema, &impl_def).iter().filter_map(|item| {
+                        match item {
+                            hir::AssocItem::Function(fn_item) => Some(fn_item),
+                            _ => None,
+                        }
+                    })
+                {
                     add_function_impl(&trigger, acc, ctx, &missing_fn);
                 }
             }
 
             SyntaxKind::TYPE_ALIAS_DEF => {
-                for missing_fn in get_missing_impl_items(&ctx.sema, &impl_def).iter().filter_map(
-                    |item| match item {
-                        hir::AssocItem::TypeAlias(type_item) => Some(type_item),
-                        _ => None,
-                    },
-                ) {
+                for missing_fn in
+                    get_missing_assoc_items(&ctx.sema, &impl_def).iter().filter_map(|item| {
+                        match item {
+                            hir::AssocItem::TypeAlias(type_item) => Some(type_item),
+                            _ => None,
+                        }
+                    })
+                {
                     add_type_alias_impl(&trigger, acc, ctx, &missing_fn);
                 }
             }
 
             SyntaxKind::CONST_DEF => {
-                for missing_fn in get_missing_impl_items(&ctx.sema, &impl_def).iter().filter_map(
-                    |item| match item {
-                        hir::AssocItem::Const(const_item) => Some(const_item),
-                        _ => None,
-                    },
-                ) {
+                for missing_fn in
+                    get_missing_assoc_items(&ctx.sema, &impl_def).iter().filter_map(|item| {
+                        match item {
+                            hir::AssocItem::Const(const_item) => Some(const_item),
+                            _ => None,
+                        }
+                    })
+                {
                     add_const_impl(&trigger, acc, ctx, &missing_fn);
                 }
             }
diff --git a/crates/ra_ide/src/completion/complete_unqualified_path.rs b/crates/ra_ide/src/completion/complete_unqualified_path.rs
index 56cd086c6..bd40af1cb 100644
--- a/crates/ra_ide/src/completion/complete_unqualified_path.rs
+++ b/crates/ra_ide/src/completion/complete_unqualified_path.rs
@@ -4,18 +4,23 @@ use hir::ScopeDef;
 use test_utils::tested_by;
 
 use crate::completion::{CompletionContext, Completions};
-use hir::{Adt, ModuleDef};
+use hir::{Adt, ModuleDef, Type};
 use ra_syntax::AstNode;
 
 pub(super) fn complete_unqualified_path(acc: &mut Completions, ctx: &CompletionContext) {
-    if (!ctx.is_trivial_path && !ctx.is_pat_binding_or_const)
-        || ctx.record_lit_syntax.is_some()
+    if !(ctx.is_trivial_path || ctx.is_pat_binding_or_const) {
+        return;
+    }
+    if ctx.record_lit_syntax.is_some()
         || ctx.record_pat_syntax.is_some()
+        || ctx.attribute_under_caret.is_some()
     {
         return;
     }
 
-    complete_enum_variants(acc, ctx);
+    if let Some(ty) = &ctx.expected_type {
+        complete_enum_variants(acc, ctx, ty);
+    }
 
     if ctx.is_pat_binding_or_const {
         return;
@@ -34,26 +39,24 @@ pub(super) fn complete_unqualified_path(acc: &mut Completions, ctx: &CompletionC
     });
 }
 
-fn complete_enum_variants(acc: &mut Completions, ctx: &CompletionContext) {
-    if let Some(ty) = ctx.expected_type_of(&ctx.token.parent()) {
-        if let Some(Adt::Enum(enum_data)) = ty.as_adt() {
-            let variants = enum_data.variants(ctx.db);
-
-            let module = if let Some(module) = ctx.scope().module() {
-                // Compute path from the completion site if available.
-                module
-            } else {
-                // Otherwise fall back to the enum's definition site.
-                enum_data.module(ctx.db)
-            };
-
-            for variant in variants {
-                if let Some(path) = module.find_use_path(ctx.db, ModuleDef::from(variant)) {
-                    // Variants with trivial paths are already added by the existing completion logic,
-                    // so we should avoid adding these twice
-                    if path.segments.len() > 1 {
-                        acc.add_enum_variant(ctx, variant, Some(path.to_string()));
-                    }
+fn complete_enum_variants(acc: &mut Completions, ctx: &CompletionContext, ty: &Type) {
+    if let Some(Adt::Enum(enum_data)) = ty.as_adt() {
+        let variants = enum_data.variants(ctx.db);
+
+        let module = if let Some(module) = ctx.scope().module() {
+            // Compute path from the completion site if available.
+            module
+        } else {
+            // Otherwise fall back to the enum's definition site.
+            enum_data.module(ctx.db)
+        };
+
+        for variant in variants {
+            if let Some(path) = module.find_use_path(ctx.db, ModuleDef::from(variant)) {
+                // Variants with trivial paths are already added by the existing completion logic,
+                // so we should avoid adding these twice
+                if path.segments.len() > 1 {
+                    acc.add_qualified_enum_variant(ctx, variant, path);
                 }
             }
         }
@@ -1173,6 +1176,7 @@ mod tests {
                 delete: 248..250,
                 insert: "Foo::Bar",
                 kind: EnumVariant,
+                lookup: "Bar",
                 detail: "()",
             },
             CompletionItem {
@@ -1181,6 +1185,7 @@ mod tests {
                 delete: 248..250,
                 insert: "Foo::Baz",
                 kind: EnumVariant,
+                lookup: "Baz",
                 detail: "()",
             },
             CompletionItem {
@@ -1189,6 +1194,7 @@ mod tests {
                 delete: 248..250,
                 insert: "Foo::Quux",
                 kind: EnumVariant,
+                lookup: "Quux",
                 detail: "()",
             },
         ]
@@ -1231,6 +1237,7 @@ mod tests {
                 delete: 219..221,
                 insert: "Foo::Bar",
                 kind: EnumVariant,
+                lookup: "Bar",
                 detail: "()",
             },
             CompletionItem {
@@ -1239,6 +1246,7 @@ mod tests {
                 delete: 219..221,
                 insert: "Foo::Baz",
                 kind: EnumVariant,
+                lookup: "Baz",
                 detail: "()",
             },
             CompletionItem {
@@ -1247,6 +1255,7 @@ mod tests {
                 delete: 219..221,
                 insert: "Foo::Quux",
                 kind: EnumVariant,
+                lookup: "Quux",
                 detail: "()",
             },
         ]
@@ -1285,6 +1294,7 @@ mod tests {
                 delete: 185..186,
                 insert: "Foo::Bar",
                 kind: EnumVariant,
+                lookup: "Bar",
                 detail: "()",
             },
             CompletionItem {
@@ -1293,6 +1303,7 @@ mod tests {
                 delete: 185..186,
                 insert: "Foo::Baz",
                 kind: EnumVariant,
+                lookup: "Baz",
                 detail: "()",
             },
             CompletionItem {
@@ -1301,6 +1312,7 @@ mod tests {
                 delete: 185..186,
                 insert: "Foo::Quux",
                 kind: EnumVariant,
+                lookup: "Quux",
                 detail: "()",
             },
             CompletionItem {
@@ -1353,10 +1365,25 @@ mod tests {
                 delete: 98..99,
                 insert: "m::E::V",
                 kind: EnumVariant,
+                lookup: "V",
                 detail: "()",
             },
         ]
         "###
         )
     }
+
+    #[test]
+    fn dont_complete_attr() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                struct Foo;
+                #[<|>]
+                fn f() {}
+                "
+            ),
+            @r###"[]"###
+        )
+    }
 }
diff --git a/crates/ra_ide/src/completion/completion_context.rs b/crates/ra_ide/src/completion/completion_context.rs
index 5f2797e41..dd87bd119 100644
--- a/crates/ra_ide/src/completion/completion_context.rs
+++ b/crates/ra_ide/src/completion/completion_context.rs
@@ -5,7 +5,7 @@ use ra_db::SourceDatabase;
 use ra_ide_db::RootDatabase;
 use ra_syntax::{
     algo::{find_covering_element, find_node_at_offset},
-    ast, AstNode,
+    ast, match_ast, AstNode,
     SyntaxKind::*,
     SyntaxNode, SyntaxToken, TextRange, TextSize,
 };
@@ -26,6 +26,7 @@ pub(crate) struct CompletionContext<'a> {
     /// The token before the cursor, in the macro-expanded file.
     pub(super) token: SyntaxToken,
     pub(super) krate: Option<hir::Crate>,
+    pub(super) expected_type: Option<Type>,
     pub(super) name_ref_syntax: Option<ast::NameRef>,
     pub(super) function_syntax: Option<ast::FnDef>,
     pub(super) use_item_syntax: Option<ast::UseItem>,
@@ -57,7 +58,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) is_macro_call: bool,
     pub(super) is_path_type: bool,
     pub(super) has_type_args: bool,
-    pub(super) is_attribute: bool,
+    pub(super) attribute_under_caret: Option<ast::Attr>,
 }
 
 impl<'a> CompletionContext<'a> {
@@ -93,6 +94,7 @@ impl<'a> CompletionContext<'a> {
             token,
             offset: position.offset,
             krate,
+            expected_type: None,
             name_ref_syntax: None,
             function_syntax: None,
             use_item_syntax: None,
@@ -114,7 +116,7 @@ impl<'a> CompletionContext<'a> {
             is_path_type: false,
             has_type_args: false,
             dot_receiver_is_ambiguous_float_literal: false,
-            is_attribute: false,
+            attribute_under_caret: None,
         };
 
         let mut original_file = original_file.syntax().clone();
@@ -175,23 +177,31 @@ impl<'a> CompletionContext<'a> {
         self.sema.scope_at_offset(&self.token.parent(), self.offset)
     }
 
-    pub(crate) fn expected_type_of(&self, node: &SyntaxNode) -> Option<Type> {
-        for ancestor in node.ancestors() {
-            if let Some(pat) = ast::Pat::cast(ancestor.clone()) {
-                return self.sema.type_of_pat(&pat);
-            } else if let Some(expr) = ast::Expr::cast(ancestor) {
-                return self.sema.type_of_expr(&expr);
-            }
-        }
-        None
-    }
-
     fn fill(
         &mut self,
         original_file: &SyntaxNode,
         file_with_fake_ident: SyntaxNode,
         offset: TextSize,
     ) {
+        // FIXME: this is wrong in at least two cases:
+        //  * when there's no token `foo(<|>)`
+        //  * when there is a token, but it happens to have type of it's own
+        self.expected_type = self
+            .token
+            .ancestors()
+            .find_map(|node| {
+                let ty = match_ast! {
+                    match node {
+                        ast::Pat(it) => self.sema.type_of_pat(&it),
+                        ast::Expr(it) => self.sema.type_of_expr(&it),
+                        _ => return None,
+                    }
+                };
+                Some(ty)
+            })
+            .flatten();
+        self.attribute_under_caret = find_node_at_offset(&file_with_fake_ident, offset);
+
         // First, let's try to complete a reference to some declaration.
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(&file_with_fake_ident, offset) {
             // Special case, `trait T { fn foo(i_am_a_name_ref) {} }`.
@@ -309,7 +319,6 @@ impl<'a> CompletionContext<'a> {
                 .and_then(|it| it.syntax().parent().and_then(ast::CallExpr::cast))
                 .is_some();
             self.is_macro_call = path.syntax().parent().and_then(ast::MacroCall::cast).is_some();
-            self.is_attribute = path.syntax().parent().and_then(ast::Attr::cast).is_some();
 
             self.is_path_type = path.syntax().parent().and_then(ast::PathType::cast).is_some();
             self.has_type_args = segment.type_arg_list().is_some();
@@ -335,7 +344,7 @@ impl<'a> CompletionContext<'a> {
                                 stmt.syntax().text_range() == name_ref.syntax().text_range(),
                             );
                         }
-                        if let Some(block) = ast::Block::cast(node) {
+                        if let Some(block) = ast::BlockExpr::cast(node) {
                             return Some(
                                 block.expr().map(|e| e.syntax().text_range())
                                     == Some(name_ref.syntax().text_range()),
diff --git a/crates/ra_ide/src/completion/presentation.rs b/crates/ra_ide/src/completion/presentation.rs
index 7633cd7fd..2edb130cf 100644
--- a/crates/ra_ide/src/completion/presentation.rs
+++ b/crates/ra_ide/src/completion/presentation.rs
@@ -1,6 +1,6 @@
 //! This modules takes care of rendering various definitions as completion items.
 
-use hir::{Docs, HasAttrs, HasSource, HirDisplay, ScopeDef, StructKind, Type};
+use hir::{Docs, HasAttrs, HasSource, HirDisplay, ModPath, ScopeDef, StructKind, Type};
 use ra_syntax::ast::NameOwner;
 use stdx::SepBy;
 use test_utils::tested_by;
@@ -246,14 +246,37 @@ impl Completions {
             .add_to(self);
     }
 
+    pub(crate) fn add_qualified_enum_variant(
+        &mut self,
+        ctx: &CompletionContext,
+        variant: hir::EnumVariant,
+        path: ModPath,
+    ) {
+        self.add_enum_variant_impl(ctx, variant, None, Some(path))
+    }
+
     pub(crate) fn add_enum_variant(
         &mut self,
         ctx: &CompletionContext,
         variant: hir::EnumVariant,
         local_name: Option<String>,
     ) {
+        self.add_enum_variant_impl(ctx, variant, local_name, None)
+    }
+
+    fn add_enum_variant_impl(
+        &mut self,
+        ctx: &CompletionContext,
+        variant: hir::EnumVariant,
+        local_name: Option<String>,
+        path: Option<ModPath>,
+    ) {
         let is_deprecated = is_deprecated(variant, ctx.db);
         let name = local_name.unwrap_or_else(|| variant.name(ctx.db).to_string());
+        let qualified_name = match &path {
+            Some(it) => it.to_string(),
+            None => name.to_string(),
+        };
         let detail_types = variant
             .fields(ctx.db)
             .into_iter()
@@ -271,16 +294,23 @@ impl Completions {
                 .surround_with("{ ", " }")
                 .to_string(),
         };
-        let mut res =
-            CompletionItem::new(CompletionKind::Reference, ctx.source_range(), name.clone())
-                .kind(CompletionItemKind::EnumVariant)
-                .set_documentation(variant.docs(ctx.db))
-                .set_deprecated(is_deprecated)
-                .detail(detail);
+        let mut res = CompletionItem::new(
+            CompletionKind::Reference,
+            ctx.source_range(),
+            qualified_name.clone(),
+        )
+        .kind(CompletionItemKind::EnumVariant)
+        .set_documentation(variant.docs(ctx.db))
+        .set_deprecated(is_deprecated)
+        .detail(detail);
+
+        if path.is_some() {
+            res = res.lookup_by(name);
+        }
 
         if variant_kind == StructKind::Tuple {
             let params = Params::Anonymous(variant.fields(ctx.db).len());
-            res = res.add_call_parens(ctx, name, params)
+            res = res.add_call_parens(ctx, qualified_name, params)
         }
 
         res.add_to(self);
@@ -349,6 +379,14 @@ impl Builder {
         if ctx.use_item_syntax.is_some() || ctx.is_call {
             return self;
         }
+
+        // Don't add parentheses if the expected type is some function reference.
+        if let Some(ty) = &ctx.expected_type {
+            if ty.is_fn() {
+                return self;
+            }
+        }
+
         let cap = match ctx.config.snippet_cap {
             Some(it) => it,
             None => return self,
@@ -749,6 +787,54 @@ mod tests {
     }
 
     #[test]
+    fn no_call_parens_if_fn_ptr_needed() {
+        assert_debug_snapshot!(
+            do_reference_completion(
+                r"
+                fn somefn(with: u8, a: u8, lot: u8, of: u8, args: u8) {}
+
+                struct ManualVtable {
+                    method: fn(u8, u8, u8, u8, u8),
+                }
+
+                fn main() -> ManualVtable {
+                    ManualVtable {
+                        method: some<|>
+                    }
+                }
+                "
+            ),
+            @r###"
+        [
+            CompletionItem {
+                label: "ManualVtable",
+                source_range: 295..299,
+                delete: 295..299,
+                insert: "ManualVtable",
+                kind: Struct,
+            },
+            CompletionItem {
+                label: "main",
+                source_range: 295..299,
+                delete: 295..299,
+                insert: "main",
+                kind: Function,
+                detail: "fn main() -> ManualVtable",
+            },
+            CompletionItem {
+                label: "somefn",
+                source_range: 295..299,
+                delete: 295..299,
+                insert: "somefn",
+                kind: Function,
+                detail: "fn somefn(with: u8, a: u8, lot: u8, of: u8, args: u8)",
+            },
+        ]
+        "###
+        );
+    }
+
+    #[test]
     fn arg_snippets_for_method_call() {
         assert_debug_snapshot!(
             do_reference_completion(
@@ -1179,7 +1265,7 @@ mod tests {
 
     #[test]
     fn test_struct_field_completion_in_record_lit() {
-        covers!(test_struct_field_completion_in_func_call);
+        covers!(test_struct_field_completion_in_record_lit);
         assert_debug_snapshot!(
         do_reference_completion(
                 r"