9 files changed, 292 insertions, 57 deletions

diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index d3caeef4e..3bf722d2a 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -76,9 +76,11 @@ impl PathResolution {
     pub fn assoc_type_shorthand_candidates<R>(
         &self,
         db: &dyn HirDatabase,
-        mut cb: impl FnMut(TypeAlias) -> Option<R>,
+        mut cb: impl FnMut(&Name, TypeAlias) -> Option<R>,
     ) -> Option<R> {
-        associated_type_shorthand_candidates(db, self.in_type_ns()?, |_, _, id| cb(id.into()))
+        associated_type_shorthand_candidates(db, self.in_type_ns()?, |name, _, id| {
+            cb(name, id.into())
+        })
     }
 }
 
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 37d162b32..8e9ea0a03 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -20,7 +20,7 @@ use hir_def::{
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
 use hir_ty::{
     diagnostics::{record_literal_missing_fields, record_pattern_missing_fields},
-    InferenceResult, Substitution,
+    InferenceResult, Substitution, TyLoweringContext,
 };
 use syntax::{
     ast::{self, AstNode},
@@ -466,7 +466,21 @@ fn resolve_hir_path_(
     prefer_value_ns: bool,
 ) -> Option<PathResolution> {
     let types = || {
-        resolver.resolve_path_in_type_ns_fully(db.upcast(), path.mod_path()).map(|ty| match ty {
+        let (ty, unresolved) = match path.type_anchor() {
+            Some(type_ref) => {
+                let (_, res) = TyLoweringContext::new(db, resolver).lower_ty_ext(type_ref);
+                res.map(|ty_ns| (ty_ns, path.segments().first()))
+            }
+            None => {
+                let (ty, remaining) =
+                    resolver.resolve_path_in_type_ns(db.upcast(), path.mod_path())?;
+                match remaining {
+                    Some(remaining) if remaining > 1 => None,
+                    _ => Some((ty, path.segments().get(1))),
+                }
+            }
+        }?;
+        let res = match ty {
             TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
             TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
             TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => {
@@ -476,7 +490,17 @@ fn resolve_hir_path_(
             TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
             TypeNs::BuiltinType(it) => PathResolution::Def(BuiltinType::from(it).into()),
             TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
-        })
+        };
+        match unresolved {
+            Some(unresolved) => res
+                .assoc_type_shorthand_candidates(db, |name, alias| {
+                    (name == unresolved.name).then(|| alias)
+                })
+                .map(TypeAlias::from)
+                .map(Into::into)
+                .map(PathResolution::Def),
+            None => Some(res),
+        }
     };
 
     let body_owner = resolver.body_owner();
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index afbfa12d5..14f34d73c 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -146,7 +146,7 @@ impl<'a> TyLoweringContext<'a> {
         self.lower_ty_ext(type_ref).0
     }
 
-    fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
+    pub fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
         let mut res = None;
         let ty = match type_ref {
             TypeRef::Never => TyKind::Never.intern(&Interner),
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index 5f9edb476..28e2e17dc 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -3834,4 +3834,67 @@ fn foo() {}
             "#]],
         );
     }
+
+    #[test]
+    fn hover_generic_assoc() {
+        check(
+            r#"
+fn foo<T: A>() where T::Assoc$0: {}
+
+trait A {
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+        check(
+            r#"
+fn foo<T: A>() {
+    let _: <T>::Assoc$0;
+}
+
+trait A {
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+        check(
+            r#"
+trait A where
+    Self::Assoc$0: ,
+{
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+    }
 }
diff --git a/crates/ide_completion/src/completions/qualified_path.rs b/crates/ide_completion/src/completions/qualified_path.rs
index 1891eb5b3..969249df6 100644
--- a/crates/ide_completion/src/completions/qualified_path.rs
+++ b/crates/ide_completion/src/completions/qualified_path.rs
@@ -24,7 +24,7 @@ pub(crate) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
     };
 
     // Add associated types on type parameters and `Self`.
-    resolution.assoc_type_shorthand_candidates(ctx.db, |alias| {
+    resolution.assoc_type_shorthand_candidates(ctx.db, |_, alias| {
         acc.add_type_alias(ctx, alias);
         None::<()>
     });
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt b/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
index f999848a7..c847bbb35 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
@@ -13,16 +13,16 @@
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
-                    line: 264,
+                    line: 271,
                     character: 8,
                 },
                 end: Position {
-                    line: 264,
-                    character: 76,
+                    line: 271,
+                    character: 50,
                 },
             },
             severity: Some(
-                Error,
+                Hint,
             ),
             code: None,
             code_description: None,
@@ -40,18 +40,18 @@
                                 password: None,
                                 host: None,
                                 port: None,
-                                path: "/test/crates/hir_def/src/data.rs",
+                                path: "/test/crates/hir_def/src/path.rs",
                                 query: None,
                                 fragment: None,
                             },
                             range: Range {
                                 start: Position {
-                                    line: 79,
-                                    character: 15,
+                                    line: 264,
+                                    character: 8,
                                 },
                                 end: Position {
-                                    line: 79,
-                                    character: 41,
+                                    line: 264,
+                                    character: 76,
                                 },
                             },
                         },
@@ -87,6 +87,71 @@
                 },
             },
             severity: Some(
+                Hint,
+            ),
+            code: None,
+            code_description: None,
+            source: Some(
+                "rustc",
+            ),
+            message: "Please register your known path in the path module",
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: Url {
+                                scheme: "file",
+                                username: "",
+                                password: None,
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/path.rs",
+                                query: None,
+                                fragment: None,
+                            },
+                            range: Range {
+                                start: Position {
+                                    line: 264,
+                                    character: 8,
+                                },
+                                end: Position {
+                                    line: 264,
+                                    character: 76,
+                                },
+                            },
+                        },
+                        message: "Exact error occurred here",
+                    },
+                ],
+            ),
+            tags: None,
+            data: None,
+        },
+        fixes: [],
+    },
+    MappedRustDiagnostic {
+        url: Url {
+            scheme: "file",
+            username: "",
+            password: None,
+            host: None,
+            port: None,
+            path: "/test/crates/hir_def/src/path.rs",
+            query: None,
+            fragment: None,
+        },
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 264,
+                    character: 8,
+                },
+                end: Position {
+                    line: 264,
+                    character: 76,
+                },
+            },
+            severity: Some(
                 Error,
             ),
             code: None,
@@ -95,7 +160,60 @@
                 "rustc",
             ),
             message: "Please register your known path in the path module",
-            related_information: None,
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: Url {
+                                scheme: "file",
+                                username: "",
+                                password: None,
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/path.rs",
+                                query: None,
+                                fragment: None,
+                            },
+                            range: Range {
+                                start: Position {
+                                    line: 271,
+                                    character: 8,
+                                },
+                                end: Position {
+                                    line: 271,
+                                    character: 50,
+                                },
+                            },
+                        },
+                        message: "Error originated from macro call here",
+                    },
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: Url {
+                                scheme: "file",
+                                username: "",
+                                password: None,
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/data.rs",
+                                query: None,
+                                fragment: None,
+                            },
+                            range: Range {
+                                start: Position {
+                                    line: 79,
+                                    character: 15,
+                                },
+                                end: Position {
+                                    line: 79,
+                                    character: 41,
+                                },
+                            },
+                        },
+                        message: "Error originated from macro call here",
+                    },
+                ],
+            ),
             tags: None,
             data: None,
         },
diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
index 76994de71..e2f319f6b 100644
--- a/crates/rust-analyzer/src/diagnostics/to_proto.rs
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -34,22 +34,14 @@ fn diagnostic_severity(
     Some(res)
 }
 
-/// Check whether a file name is from macro invocation
-fn is_from_macro(file_name: &str) -> bool {
+/// Checks whether a file name is from macro invocation and does not refer to an actual file.
+fn is_dummy_macro_file(file_name: &str) -> bool {
+    // FIXME: current rustc does not seem to emit `<macro file>` files anymore?
     file_name.starts_with('<') && file_name.ends_with('>')
 }
 
-/// Converts a Rust span to a LSP location, resolving macro expansion site if neccesary
-fn location(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
-    let mut span = span.clone();
-    while let Some(expansion) = span.expansion {
-        span = expansion.span;
-    }
-    return location_naive(workspace_root, &span);
-}
-
 /// Converts a Rust span to a LSP location
-fn location_naive(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
+fn location(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
     let file_name = workspace_root.join(&span.file_name);
     let uri = url_from_abs_path(&file_name);
 
@@ -62,7 +54,25 @@ fn location_naive(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Lo
     lsp_types::Location { uri, range }
 }
 
-/// Converts a secondary Rust span to a LSP related inflocation(ormation
+/// Extracts a suitable "primary" location from a rustc diagnostic.
+///
+/// This takes locations pointing into the standard library, or generally outside the current
+/// workspace into account and tries to avoid those, in case macros are involved.
+fn primary_location(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
+    let span_stack = std::iter::successors(Some(span), |span| Some(&span.expansion.as_ref()?.span));
+    for span in span_stack.clone() {
+        let abs_path = workspace_root.join(&span.file_name);
+        if !is_dummy_macro_file(&span.file_name) && abs_path.starts_with(workspace_root) {
+            return location(workspace_root, span);
+        }
+    }
+
+    // Fall back to the outermost macro invocation if no suitable span comes up.
+    let last_span = span_stack.last().unwrap();
+    location(workspace_root, last_span)
+}
+
+/// Converts a secondary Rust span to a LSP related information
 ///
 /// If the span is unlabelled this will return `None`.
 fn diagnostic_related_information(
@@ -231,7 +241,7 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
     primary_spans
         .iter()
         .flat_map(|primary_span| {
-            let location = location(workspace_root, &primary_span);
+            let primary_location = primary_location(workspace_root, &primary_span);
 
             let mut message = message.clone();
             if needs_primary_span_label {
@@ -243,31 +253,47 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
             // Each primary diagnostic span may result in multiple LSP diagnostics.
             let mut diagnostics = Vec::new();
 
-            let mut related_macro_info = None;
+            let mut related_info_macro_calls = vec![];
 
             // If error occurs from macro expansion, add related info pointing to
             // where the error originated
             // Also, we would generate an additional diagnostic, so that exact place of macro
             // will be highlighted in the error origin place.
-            if !is_from_macro(&primary_span.file_name) && primary_span.expansion.is_some() {
-                let in_macro_location = location_naive(workspace_root, &primary_span);
+            let span_stack = std::iter::successors(Some(*primary_span), |span| {
+                Some(&span.expansion.as_ref()?.span)
+            });
+            for (i, span) in span_stack.enumerate() {
+                if is_dummy_macro_file(&span.file_name) {
+                    continue;
+                }
 
-                // Add related information for the main disagnostic.
-                related_macro_info = Some(lsp_types::DiagnosticRelatedInformation {
-                    location: in_macro_location.clone(),
-                    message: "Error originated from macro here".to_string(),
-                });
+                // First span is the original diagnostic, others are macro call locations that
+                // generated that code.
+                let is_in_macro_call = i != 0;
 
+                let secondary_location = location(workspace_root, &span);
+                if secondary_location == primary_location {
+                    continue;
+                }
+                related_info_macro_calls.push(lsp_types::DiagnosticRelatedInformation {
+                    location: secondary_location.clone(),
+                    message: if is_in_macro_call {
+                        "Error originated from macro call here".to_string()
+                    } else {
+                        "Actual error occurred here".to_string()
+                    },
+                });
                 // For the additional in-macro diagnostic we add the inverse message pointing to the error location in code.
                 let information_for_additional_diagnostic =
                     vec![lsp_types::DiagnosticRelatedInformation {
-                        location: location.clone(),
+                        location: primary_location.clone(),
                         message: "Exact error occurred here".to_string(),
                     }];
 
                 let diagnostic = lsp_types::Diagnostic {
-                    range: in_macro_location.range,
-                    severity,
+                    range: secondary_location.range,
+                    // downgrade to hint if we're pointing at the macro
+                    severity: Some(lsp_types::DiagnosticSeverity::Hint),
                     code: code.clone().map(lsp_types::NumberOrString::String),
                     code_description: code_description.clone(),
                     source: Some(source.clone()),
@@ -276,9 +302,8 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
                     tags: if tags.is_empty() { None } else { Some(tags.clone()) },
                     data: None,
                 };
-
                 diagnostics.push(MappedRustDiagnostic {
-                    url: in_macro_location.uri,
+                    url: secondary_location.uri,
                     diagnostic,
                     fixes: Vec::new(),
                 });
@@ -286,23 +311,25 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
 
             // Emit the primary diagnostic.
             diagnostics.push(MappedRustDiagnostic {
-                url: location.uri.clone(),
+                url: primary_location.uri.clone(),
                 diagnostic: lsp_types::Diagnostic {
-                    range: location.range,
+                    range: primary_location.range,
                     severity,
                     code: code.clone().map(lsp_types::NumberOrString::String),
                     code_description: code_description.clone(),
                     source: Some(source.clone()),
                     message,
-                    related_information: if subdiagnostics.is_empty() {
-                        None
-                    } else {
-                        let mut related = subdiagnostics
+                    related_information: {
+                        let info = related_info_macro_calls
                             .iter()
-                            .map(|sub| sub.related.clone())
+                            .cloned()
+                            .chain(subdiagnostics.iter().map(|sub| sub.related.clone()))
                             .collect::<Vec<_>>();
-                        related.extend(related_macro_info);
-                        Some(related)
+                        if info.is_empty() {
+                            None
+                        } else {
+                            Some(info)
+                        }
                     },
                     tags: if tags.is_empty() { None } else { Some(tags.clone()) },
                     data: None,
@@ -314,7 +341,7 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
             // This is useful because they will show up in the user's editor, unlike
             // `related_information`, which just produces hard-to-read links, at least in VS Code.
             let back_ref = lsp_types::DiagnosticRelatedInformation {
-                location,
+                location: primary_location,
                 message: "original diagnostic".to_string(),
             };
             for sub in &subdiagnostics {
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 85e67554c..53d29ddfc 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -84,7 +84,8 @@ pub(crate) fn handle_analyzer_status(
 
 pub(crate) fn handle_memory_usage(state: &mut GlobalState, _: ()) -> Result<String> {
     let _p = profile::span("handle_memory_usage");
-    let mem = state.analysis_host.per_query_memory_usage();
+    let mut mem = state.analysis_host.per_query_memory_usage();
+    mem.push(("Remaining".into(), profile::memory_usage().allocated));
 
     let mut out = String::new();
     for (name, bytes) in mem {
diff --git a/docs/dev/style.md b/docs/dev/style.md
index e4a1672ca..1b1c24b1e 100644
--- a/docs/dev/style.md
+++ b/docs/dev/style.md
@@ -55,9 +55,9 @@ https://www.tedinski.com/2018/02/06/system-boundaries.html
 We try to be very conservative with usage of crates.io dependencies.
 Don't use small "helper" crates (exception: `itertools` is allowed).
 If there's some general reusable bit of code you need, consider adding it to the `stdx` crate.
+A useful exercise is to read Cargo.lock and see if some of the *transitive* dependencies do not make sense for rust-analyzer.
 
-**Rationale:** keep compile times low, create ecosystem pressure for faster
-compiles, reduce the number of things which might break.
+**Rationale:** keep compile times low, create ecosystem pressure for faster compiles, reduce the number of things which might break.
 
 ## Commit Style