4 files changed, 115 insertions, 16 deletions

diff --git a/crates/ra_assists/src/auto_import.rs b/crates/ra_assists/src/auto_import.rs
index b251c9369..52c2a0b2b 100644
--- a/crates/ra_assists/src/auto_import.rs
+++ b/crates/ra_assists/src/auto_import.rs
@@ -1,6 +1,6 @@
 use hir::db::HirDatabase;
 use ra_syntax::{
-    ast, AstNode, SyntaxNode, Direction, TextRange,
+    ast::{ self, NameOwner }, AstNode, SyntaxNode, Direction, TextRange,
     SyntaxKind::{ PATH, PATH_SEGMENT, COLONCOLON, COMMA }
 };
 use crate::assist_ctx::{AssistCtx, Assist, AssistBuilder};
@@ -345,9 +345,9 @@ fn best_action_for_target<'b, 'a: 'b>(
     match best_action {
         Some(action) => return action,
         None => {
-            // We have no action we no use item was found in container so we find
+            // We have no action and no UseItem was found in container so we find
             // another item and we use it as anchor.
-            // If there are not items, we choose the target path itself as anchor.
+            // If there are no items, we choose the target path itself as anchor.
             let anchor = container
                 .children()
                 .find_map(ast::ModuleItem::cast)
@@ -480,6 +480,24 @@ fn make_assist_add_nested_import(
     }
 }
 
+fn apply_auto_import<'a>(
+    container: &SyntaxNode,
+    path: &ast::Path,
+    target: &[&'a ast::PathSegment],
+    edit: &mut AssistBuilder,
+) {
+    let action = best_action_for_target(container, path, target);
+    make_assist(&action, target, edit);
+    if let (Some(first), Some(last)) = (target.first(), target.last()) {
+        // Here we are assuming the assist will provide a  correct use statement
+        // so we can delete the path qualifier
+        edit.delete(TextRange::from_to(
+            first.syntax().range().start(),
+            last.syntax().range().start(),
+        ));
+    }
+}
+
 pub(crate) fn auto_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let node = ctx.covering_node();
     let current_file = node.ancestors().find_map(ast::SourceFile::cast)?;
@@ -495,18 +513,20 @@ pub(crate) fn auto_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist
         return None;
     }
 
-    ctx.add_action(format!("import {} in the current file", fmt_segments(&segments)), |edit| {
-        let action = best_action_for_target(current_file.syntax(), path, &segments);
-        make_assist(&action, segments.as_slice(), edit);
-        if let Some(last_segment) = path.segment() {
-            // Here we are assuming the assist will provide a  correct use statement
-            // so we can delete the path qualifier
-            edit.delete(TextRange::from_to(
-                path.syntax().range().start(),
-                last_segment.syntax().range().start(),
-            ));
+    if let Some(module) = path.syntax().ancestors().find_map(ast::Module::cast) {
+        if let (Some(item_list), Some(name)) = (module.item_list(), module.name()) {
+            ctx.add_action(
+                format!("import {} in mod {}", fmt_segments(&segments), name.text()),
+                |edit| {
+                    apply_auto_import(item_list.syntax(), path, &segments, edit);
+                },
+            );
         }
-    });
+    } else {
+        ctx.add_action(format!("import {} in the current file", fmt_segments(&segments)), |edit| {
+            apply_auto_import(current_file.syntax(), path, &segments, edit);
+        });
+    }
 
     ctx.build()
 }
@@ -532,6 +552,21 @@ Debug<|>
     }
 
     #[test]
+    fn test_auto_import_file_add_use_no_anchor_2seg() {
+        check_assist(
+            auto_import,
+            "
+std::fmt<|>::Debug
+    ",
+            "
+use std::fmt;
+
+fmt<|>::Debug
+    ",
+        );
+    }
+
+    #[test]
     fn test_auto_import_file_add_use() {
         check_assist(
             auto_import,
@@ -728,4 +763,37 @@ impl foo<|> for Foo {
 ",
         );
     }
+
+    #[test]
+    fn test_auto_import_not_applicable_in_use() {
+        check_assist_not_applicable(
+            auto_import,
+            "
+use std::fmt<|>;
+",
+        );
+    }
+
+    #[test]
+    fn test_auto_import_file_add_use_no_anchor_in_mod_mod() {
+        check_assist(
+            auto_import,
+            "
+mod foo {
+    mod bar {
+        std::fmt::Debug<|>
+    }
+}
+    ",
+            "
+mod foo {
+    mod bar {
+        use std::fmt::Debug;
+
+        Debug<|>
+    }
+}
+    ",
+        );
+    }
 }
diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 2dc1de41a..f28a7e731 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -450,7 +450,6 @@ impl Ty {
     }
 
     pub fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        f(self);
         match self {
             Ty::Slice(t) | Ty::Array(t) => t.walk(f),
             Ty::RawPtr(t, _) => t.walk(f),
@@ -490,10 +489,10 @@ impl Ty {
             | Ty::Infer(_)
             | Ty::Unknown => {}
         }
+        f(self);
     }
 
     fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
-        f(self);
         match self {
             Ty::Slice(t) | Ty::Array(t) => Arc::make_mut(t).walk_mut(f),
             Ty::RawPtr(t, _) => Arc::make_mut(t).walk_mut(f),
@@ -544,6 +543,7 @@ impl Ty {
             | Ty::Infer(_)
             | Ty::Unknown => {}
         }
+        f(self);
     }
 
     fn fold(mut self, f: &mut impl FnMut(Ty) -> Ty) -> Ty {
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_nested_generics_crash.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_nested_generics_crash.snap
new file mode 100644
index 000000000..209454a91
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_nested_generics_crash.snap
@@ -0,0 +1,12 @@
+---
+created: "2019-02-11T21:59:04.302375838Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[92; 106) 'query_response': Canonical<QueryResponse<R>>
+[137; 167) '{     ...lue; }': ()
+[143; 164) '&query....value': &QueryResponse<R>
+[144; 158) 'query_response': Canonical<QueryResponse<R>>
+[144; 164) 'query_....value': QueryResponse<R>
+
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index e64fd2749..203f1fe4d 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -719,6 +719,25 @@ fn extra_compiler_flags() {
     );
 }
 
+#[test]
+fn infer_nested_generics_crash() {
+    // another crash found typechecking rustc
+    check_inference(
+        "infer_nested_generics_crash",
+        r#"
+struct Canonical<V> {
+    value: V,
+}
+struct QueryResponse<V> {
+    value: V,
+}
+fn test<R>(query_response: Canonical<QueryResponse<R>>) {
+    &query_response.value;
+}
+"#,
+    );
+}
+
 fn infer(content: &str) -> String {
     let (db, _, file_id) = MockDatabase::with_single_file(content);
     let source_file = db.parse(file_id);