15 files changed, 224 insertions, 59 deletions

diff --git a/crates/ra_assists/src/handlers/add_turbo_fish.rs b/crates/ra_assists/src/handlers/add_turbo_fish.rs
index 0c565e89a..537322a72 100644
--- a/crates/ra_assists/src/handlers/add_turbo_fish.rs
+++ b/crates/ra_assists/src/handlers/add_turbo_fish.rs
@@ -41,7 +41,7 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext) -> Option<(
     let name_ref = ast::NameRef::cast(ident.parent())?;
     let def = match classify_name_ref(&ctx.sema, &name_ref)? {
         NameRefClass::Definition(def) => def,
-        NameRefClass::FieldShorthand { .. } => return None,
+        NameRefClass::ExternCrate(_) | NameRefClass::FieldShorthand { .. } => return None,
     };
     let fun = match def {
         Definition::ModuleDef(hir::ModuleDef::Function(it)) => it,
diff --git a/crates/ra_assists/src/utils.rs b/crates/ra_assists/src/utils.rs
index 54d5678d1..0de6fdf3f 100644
--- a/crates/ra_assists/src/utils.rs
+++ b/crates/ra_assists/src/utils.rs
@@ -257,7 +257,7 @@ pub use prelude::*;
             .find(|dep| &dep.name.to_string() == std_crate)?
             .krate;
 
-        let mut module = std_crate.root_module(db)?;
+        let mut module = std_crate.root_module(db);
         for segment in path {
             module = module.children(db).find_map(|child| {
                 let name = child.name(db)?;
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 27cdabea0..44456e49e 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -83,9 +83,9 @@ impl Crate {
             .collect()
     }
 
-    pub fn root_module(self, db: &dyn HirDatabase) -> Option<Module> {
+    pub fn root_module(self, db: &dyn HirDatabase) -> Module {
         let module_id = db.crate_def_map(self.id).root;
-        Some(Module::new(self, module_id))
+        Module::new(self, module_id)
     }
 
     pub fn root_file(self, db: &dyn HirDatabase) -> FileId {
diff --git a/crates/ra_hir/src/semantics.rs b/crates/ra_hir/src/semantics.rs
index 307b336f2..e392130ab 100644
--- a/crates/ra_hir/src/semantics.rs
+++ b/crates/ra_hir/src/semantics.rs
@@ -8,7 +8,7 @@ use hir_def::{
     resolver::{self, HasResolver, Resolver},
     AsMacroCall, FunctionId, TraitId, VariantId,
 };
-use hir_expand::{diagnostics::AstDiagnostic, hygiene::Hygiene, ExpansionInfo};
+use hir_expand::{diagnostics::AstDiagnostic, hygiene::Hygiene, name::AsName, ExpansionInfo};
 use hir_ty::associated_type_shorthand_candidates;
 use itertools::Itertools;
 use ra_db::{FileId, FileRange};
@@ -24,8 +24,8 @@ use crate::{
     diagnostics::Diagnostic,
     semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
     source_analyzer::{resolve_hir_path, resolve_hir_path_qualifier, SourceAnalyzer},
-    AssocItem, Callable, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef, Module,
-    ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, VariantDef,
+    AssocItem, Callable, Crate, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef,
+    Module, ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, VariantDef,
 };
 use resolver::TypeNs;
 
@@ -228,6 +228,10 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.imp.resolve_path(path)
     }
 
+    pub fn resolve_extern_crate(&self, extern_crate: &ast::ExternCrate) -> Option<Crate> {
+        self.imp.resolve_extern_crate(extern_crate)
+    }
+
     pub fn resolve_variant(&self, record_lit: ast::RecordExpr) -> Option<VariantDef> {
         self.imp.resolve_variant(record_lit).map(VariantDef::from)
     }
@@ -443,6 +447,17 @@ impl<'db> SemanticsImpl<'db> {
         self.analyze(path.syntax()).resolve_path(self.db, path)
     }
 
+    fn resolve_extern_crate(&self, extern_crate: &ast::ExternCrate) -> Option<Crate> {
+        let krate = self.scope(extern_crate.syntax()).krate()?;
+        krate.dependencies(self.db).into_iter().find_map(|dep| {
+            if dep.name == extern_crate.name_ref()?.as_name() {
+                Some(dep.krate)
+            } else {
+                None
+            }
+        })
+    }
+
     fn resolve_variant(&self, record_lit: ast::RecordExpr) -> Option<VariantId> {
         self.analyze(record_lit.syntax()).resolve_variant(self.db, record_lit)
     }
@@ -612,6 +627,10 @@ impl<'a> SemanticsScope<'a> {
         Some(Module { id: self.resolver.module()? })
     }
 
+    pub fn krate(&self) -> Option<Crate> {
+        Some(Crate { id: self.resolver.krate()? })
+    }
+
     /// Note: `FxHashSet<TraitId>` should be treated as an opaque type, passed into `Type
     // FIXME: rename to visible_traits to not repeat scope?
     pub fn traits_in_scope(&self) -> FxHashSet<TraitId> {
diff --git a/crates/ra_ide/src/display/short_label.rs b/crates/ra_ide/src/display/short_label.rs
index 0fdf8e9a5..b5ff9fa2d 100644
--- a/crates/ra_ide/src/display/short_label.rs
+++ b/crates/ra_ide/src/display/short_label.rs
@@ -47,6 +47,12 @@ impl ShortLabel for ast::Module {
     }
 }
 
+impl ShortLabel for ast::SourceFile {
+    fn short_label(&self) -> Option<String> {
+        None
+    }
+}
+
 impl ShortLabel for ast::TypeAlias {
     fn short_label(&self) -> Option<String> {
         short_label_from_node(self, "type ")
diff --git a/crates/ra_ide/src/goto_definition.rs b/crates/ra_ide/src/goto_definition.rs
index 4e3f428fa..45389fd23 100644
--- a/crates/ra_ide/src/goto_definition.rs
+++ b/crates/ra_ide/src/goto_definition.rs
@@ -1,6 +1,6 @@
 use hir::Semantics;
 use ra_ide_db::{
-    defs::{classify_name, classify_name_ref, NameClass},
+    defs::{classify_name, classify_name_ref},
     symbol_index, RootDatabase,
 };
 use ra_syntax::{
@@ -40,10 +40,7 @@ pub(crate) fn goto_definition(
                 reference_definition(&sema, &name_ref).to_vec()
             },
             ast::Name(name) => {
-                let def = match classify_name(&sema, &name)? {
-                    NameClass::Definition(def) | NameClass::ConstReference(def) => def,
-                    NameClass::FieldShorthand { local: _, field } => field,
-                };
+                let def = classify_name(&sema, &name)?.definition(sema.db);
                 let nav = def.try_to_nav(sema.db)?;
                 vec![nav]
             },
@@ -86,8 +83,7 @@ pub(crate) fn reference_definition(
 ) -> ReferenceResult {
     let name_kind = classify_name_ref(sema, name_ref);
     if let Some(def) = name_kind {
-        let def = def.definition();
-
+        let def = def.definition(sema.db);
         return match def.try_to_nav(sema.db) {
             Some(nav) => ReferenceResult::Exact(nav),
             None => ReferenceResult::Approximate(Vec::new()),
@@ -134,6 +130,32 @@ mod tests {
     }
 
     #[test]
+    fn goto_def_for_extern_crate() {
+        check(
+            r#"
+            //- /main.rs
+            extern crate std<|>;
+            //- /std/lib.rs
+            // empty
+            //^ file
+            "#,
+        )
+    }
+
+    #[test]
+    fn goto_def_for_renamed_extern_crate() {
+        check(
+            r#"
+            //- /main.rs
+            extern crate std as abc<|>;
+            //- /std/lib.rs
+            // empty
+            //^ file
+            "#,
+        )
+    }
+
+    #[test]
     fn goto_def_in_items() {
         check(
             r#"
diff --git a/crates/ra_ide/src/hover.rs b/crates/ra_ide/src/hover.rs
index 385e3e64e..9c7348898 100644
--- a/crates/ra_ide/src/hover.rs
+++ b/crates/ra_ide/src/hover.rs
@@ -85,8 +85,8 @@ pub(crate) fn hover(db: &RootDatabase, position: FilePosition) -> Option<RangeIn
     let node = token.parent();
     let definition = match_ast! {
         match node {
-            ast::NameRef(name_ref) => classify_name_ref(&sema, &name_ref).map(|d| d.definition()),
-            ast::Name(name) => classify_name(&sema, &name).map(|d| d.definition()),
+            ast::NameRef(name_ref) => classify_name_ref(&sema, &name_ref).map(|d| d.definition(sema.db)),
+            ast::Name(name) => classify_name(&sema, &name).map(|d| d.definition(sema.db)),
             _ => None,
         }
     };
@@ -304,7 +304,10 @@ fn hover_for_definition(db: &RootDatabase, def: Definition) -> Option<Markup> {
                     let docs = Documentation::from_ast(&it).map(Into::into);
                     hover_markup(docs, it.short_label(), mod_path)
                 }
-                _ => None,
+                ModuleSource::SourceFile(it) => {
+                    let docs = Documentation::from_ast(&it).map(Into::into);
+                    hover_markup(docs, it.short_label(), mod_path)
+                }
             },
             ModuleDef::Function(it) => from_def_source(db, it, mod_path),
             ModuleDef::Adt(Adt::Struct(it)) => from_def_source(db, it, mod_path),
@@ -1138,6 +1141,46 @@ fn bar() { fo<|>o(); }
     }
 
     #[test]
+    fn test_hover_extern_crate() {
+        check(
+            r#"
+//- /main.rs
+extern crate st<|>d;
+//- /std/lib.rs
+//! Standard library for this test
+//!
+//! Printed?
+//! abc123
+            "#,
+            expect![[r#"
+            *std*
+            Standard library for this test
+
+            Printed?
+            abc123
+            "#]],
+        );
+        check(
+            r#"
+//- /main.rs
+extern crate std as ab<|>c;
+//- /std/lib.rs
+//! Standard library for this test
+//!
+//! Printed?
+//! abc123
+            "#,
+            expect![[r#"
+            *abc*
+            Standard library for this test
+
+            Printed?
+            abc123
+            "#]],
+        );
+    }
+
+    #[test]
     fn test_hover_mod_with_same_name_as_function() {
         check(
             r#"
diff --git a/crates/ra_ide/src/references.rs b/crates/ra_ide/src/references.rs
index cf456630a..453985de3 100644
--- a/crates/ra_ide/src/references.rs
+++ b/crates/ra_ide/src/references.rs
@@ -130,13 +130,13 @@ fn find_name(
     opt_name: Option<ast::Name>,
 ) -> Option<RangeInfo<Definition>> {
     if let Some(name) = opt_name {
-        let def = classify_name(sema, &name)?.definition();
+        let def = classify_name(sema, &name)?.definition(sema.db);
         let range = name.syntax().text_range();
         return Some(RangeInfo::new(range, def));
     }
     let name_ref =
         sema.find_node_at_offset_with_descend::<ast::NameRef>(&syntax, position.offset)?;
-    let def = classify_name_ref(sema, &name_ref)?.definition();
+    let def = classify_name_ref(sema, &name_ref)?.definition(sema.db);
     let range = name_ref.syntax().text_range();
     Some(RangeInfo::new(range, def))
 }
diff --git a/crates/ra_ide/src/syntax_highlighting.rs b/crates/ra_ide/src/syntax_highlighting.rs
index f71b804fe..6b7874460 100644
--- a/crates/ra_ide/src/syntax_highlighting.rs
+++ b/crates/ra_ide/src/syntax_highlighting.rs
@@ -495,6 +495,7 @@ fn highlight_element(
             };
 
             match name_kind {
+                Some(NameClass::ExternCrate(_)) => HighlightTag::Module.into(),
                 Some(NameClass::Definition(def)) => {
                     highlight_name(db, def, false) | HighlightModifier::Definition
                 }
@@ -522,6 +523,7 @@ fn highlight_element(
             let possibly_unsafe = is_possibly_unsafe(&name_ref);
             match classify_name_ref(sema, &name_ref) {
                 Some(name_kind) => match name_kind {
+                    NameRefClass::ExternCrate(_) => HighlightTag::Module.into(),
                     NameRefClass::Definition(def) => {
                         if let Definition::Local(local) = &def {
                             if let Some(name) = local.name(db) {
diff --git a/crates/ra_ide/src/syntax_highlighting/tests.rs b/crates/ra_ide/src/syntax_highlighting/tests.rs
index 730efff0d..09062c38e 100644
--- a/crates/ra_ide/src/syntax_highlighting/tests.rs
+++ b/crates/ra_ide/src/syntax_highlighting/tests.rs
@@ -391,6 +391,23 @@ macro_rules! noop {
     );
 }
 
+#[test]
+fn test_extern_crate() {
+    check_highlighting(
+        r#"
+        //- /main.rs
+        extern crate std;
+        extern crate alloc as abc;
+        //- /std/lib.rs
+        pub struct S;
+        //- /alloc/lib.rs
+        pub struct A
+        "#,
+        expect_file!["crates/ra_ide/test_data/highlight_extern_crate.html"],
+        false,
+    );
+}
+
 /// Highlights the code given by the `ra_fixture` argument, renders the
 /// result as HTML, and compares it with the HTML file given as `snapshot`.
 /// Note that the `snapshot` file is overwritten by the rendered HTML.
diff --git a/crates/ra_ide/test_data/highlight_extern_crate.html b/crates/ra_ide/test_data/highlight_extern_crate.html
new file mode 100644
index 000000000..800d894c7
--- /dev/null
+++ b/crates/ra_ide/test_data/highlight_extern_crate.html
@@ -0,0 +1,40 @@
+
+<style>
+body                { margin: 0; }
+pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padding: 0.4em; }
+
+.lifetime           { color: #DFAF8F; font-style: italic; }
+.comment            { color: #7F9F7F; }
+.documentation      { color: #629755; }
+.injected           { opacity: 0.65 ; }
+.struct, .enum      { color: #7CB8BB; }
+.enum_variant       { color: #BDE0F3; }
+.string_literal     { color: #CC9393; }
+.field              { color: #94BFF3; }
+.function           { color: #93E0E3; }
+.function.unsafe    { color: #BC8383; }
+.operator.unsafe    { color: #BC8383; }
+.parameter          { color: #94BFF3; }
+.text               { color: #DCDCCC; }
+.type               { color: #7CB8BB; }
+.builtin_type       { color: #8CD0D3; }
+.type_param         { color: #DFAF8F; }
+.attribute          { color: #94BFF3; }
+.numeric_literal    { color: #BFEBBF; }
+.bool_literal       { color: #BFE6EB; }
+.macro              { color: #94BFF3; }
+.module             { color: #AFD8AF; }
+.value_param        { color: #DCDCCC; }
+.variable           { color: #DCDCCC; }
+.format_specifier   { color: #CC696B; }
+.mutable            { text-decoration: underline; }
+.escape_sequence    { color: #94BFF3; }
+.keyword            { color: #F0DFAF; font-weight: bold; }
+.keyword.unsafe     { color: #BC8383; font-weight: bold; }
+.control            { font-style: italic; }
+
+.unresolved_reference { color: #FC5555; text-decoration: wavy underline; }
+</style>
+<pre><code><span class="keyword">extern</span> <span class="keyword">crate</span> <span class="module">std</span><span class="punctuation">;</span>
+<span class="keyword">extern</span> <span class="keyword">crate</span> <span class="module">alloc</span> <span class="keyword">as</span> <span class="module">abc</span><span class="punctuation">;</span>
+</code></pre>
\ No newline at end of file
diff --git a/crates/ra_ide_db/src/defs.rs b/crates/ra_ide_db/src/defs.rs
index b51000b03..9bb95277d 100644
--- a/crates/ra_ide_db/src/defs.rs
+++ b/crates/ra_ide_db/src/defs.rs
@@ -6,8 +6,8 @@
 // FIXME: this badly needs rename/rewrite (matklad, 2020-02-06).
 
 use hir::{
-    Field, HasVisibility, ImplDef, Local, MacroDef, Module, ModuleDef, Name, PathResolution,
-    Semantics, TypeParam, Visibility,
+    db::HirDatabase, Crate, Field, HasVisibility, ImplDef, Local, MacroDef, Module, ModuleDef,
+    Name, PathResolution, Semantics, TypeParam, Visibility,
 };
 use ra_prof::profile;
 use ra_syntax::{
@@ -80,6 +80,7 @@ impl Definition {
 
 #[derive(Debug)]
 pub enum NameClass {
+    ExternCrate(Crate),
     Definition(Definition),
     /// `None` in `if let None = Some(82) {}`
     ConstReference(Definition),
@@ -90,16 +91,18 @@ pub enum NameClass {
 }
 
 impl NameClass {
-    pub fn into_definition(self) -> Option<Definition> {
-        match self {
-            NameClass::Definition(it) => Some(it),
-            NameClass::ConstReference(_) => None,
-            NameClass::FieldShorthand { local, field: _ } => Some(Definition::Local(local)),
-        }
+    pub fn into_definition(self, db: &dyn HirDatabase) -> Option<Definition> {
+        Some(match self {
+            NameClass::ExternCrate(krate) => Definition::ModuleDef(krate.root_module(db).into()),
+            NameClass::Definition(it) => it,
+            NameClass::ConstReference(_) => return None,
+            NameClass::FieldShorthand { local, field: _ } => Definition::Local(local),
+        })
     }
 
-    pub fn definition(self) -> Definition {
+    pub fn definition(self, db: &dyn HirDatabase) -> Definition {
         match self {
+            NameClass::ExternCrate(krate) => Definition::ModuleDef(krate.root_module(db).into()),
             NameClass::Definition(it) | NameClass::ConstReference(it) => it,
             NameClass::FieldShorthand { local: _, field } => field,
         }
@@ -120,32 +123,37 @@ pub fn classify_name(sema: &Semantics<RootDatabase>, name: &ast::Name) -> Option
     match_ast! {
         match parent {
             ast::Rename(it) => {
-                let use_tree = it.syntax().parent().and_then(ast::UseTree::cast)?;
-                let path = use_tree.path()?;
-                let path_segment = path.segment()?;
-                let name_ref_class = path_segment
-                    .name_ref()
-                    // The rename might be from a `self` token, so fallback to the name higher
-                    // in the use tree.
-                    .or_else(||{
-                        if path_segment.self_token().is_none() {
-                            return None;
-                        }
+                if let Some(use_tree) = it.syntax().parent().and_then(ast::UseTree::cast) {
+                    let path = use_tree.path()?;
+                    let path_segment = path.segment()?;
+                    let name_ref_class = path_segment
+                        .name_ref()
+                        // The rename might be from a `self` token, so fallback to the name higher
+                        // in the use tree.
+                        .or_else(||{
+                            if path_segment.self_token().is_none() {
+                                return None;
+                            }
 
-                        let use_tree = use_tree
-                            .syntax()
-                            .parent()
-                            .as_ref()
-                            // Skip over UseTreeList
-                            .and_then(SyntaxNode::parent)
-                            .and_then(ast::UseTree::cast)?;
-                        let path = use_tree.path()?;
-                        let path_segment = path.segment()?;
-                        path_segment.name_ref()
-                    })
-                    .and_then(|name_ref| classify_name_ref(sema, &name_ref))?;
+                            let use_tree = use_tree
+                                .syntax()
+                                .parent()
+                                .as_ref()
+                                // Skip over UseTreeList
+                                .and_then(SyntaxNode::parent)
+                                .and_then(ast::UseTree::cast)?;
+                            let path = use_tree.path()?;
+                            let path_segment = path.segment()?;
+                            path_segment.name_ref()
+                        })
+                        .and_then(|name_ref| classify_name_ref(sema, &name_ref))?;
 
-                Some(NameClass::Definition(name_ref_class.definition()))
+                    Some(NameClass::Definition(name_ref_class.definition(sema.db)))
+                } else {
+                    let extern_crate = it.syntax().parent().and_then(ast::ExternCrate::cast)?;
+                    let resolved = sema.resolve_extern_crate(&extern_crate)?;
+                    Some(NameClass::ExternCrate(resolved))
+                }
             },
             ast::IdentPat(it) => {
                 let local = sema.to_def(&it)?;
@@ -220,13 +228,15 @@ pub fn classify_name(sema: &Semantics<RootDatabase>, name: &ast::Name) -> Option
 
 #[derive(Debug)]
 pub enum NameRefClass {
+    ExternCrate(Crate),
     Definition(Definition),
     FieldShorthand { local: Local, field: Definition },
 }
 
 impl NameRefClass {
-    pub fn definition(self) -> Definition {
+    pub fn definition(self, db: &dyn HirDatabase) -> Definition {
         match self {
+            NameRefClass::ExternCrate(krate) => Definition::ModuleDef(krate.root_module(db).into()),
             NameRefClass::Definition(def) => def,
             NameRefClass::FieldShorthand { local, field: _ } => Definition::Local(local),
         }
@@ -307,9 +317,15 @@ pub fn classify_name_ref(
         }
     }
 
-    let path = name_ref.syntax().ancestors().find_map(ast::Path::cast)?;
-    let resolved = sema.resolve_path(&path)?;
-    Some(NameRefClass::Definition(resolved.into()))
+    if let Some(path) = name_ref.syntax().ancestors().find_map(ast::Path::cast) {
+        if let Some(resolved) = sema.resolve_path(&path) {
+            return Some(NameRefClass::Definition(resolved.into()));
+        }
+    }
+
+    let extern_crate = ast::ExternCrate::cast(parent)?;
+    let resolved = sema.resolve_extern_crate(&extern_crate)?;
+    Some(NameRefClass::ExternCrate(resolved))
 }
 
 impl From<PathResolution> for Definition {
diff --git a/crates/ra_ide_db/src/imports_locator.rs b/crates/ra_ide_db/src/imports_locator.rs
index 1fba71ff8..9e040973b 100644
--- a/crates/ra_ide_db/src/imports_locator.rs
+++ b/crates/ra_ide_db/src/imports_locator.rs
@@ -61,5 +61,5 @@ fn get_name_definition<'a>(
         candidate_node
     };
     let name = ast::Name::cast(candidate_name_node)?;
-    classify_name(sema, &name)?.into_definition()
+    classify_name(sema, &name)?.into_definition(sema.db)
 }
diff --git a/crates/rust-analyzer/src/cli/analysis_stats.rs b/crates/rust-analyzer/src/cli/analysis_stats.rs
index 721d41a58..0d386841e 100644
--- a/crates/rust-analyzer/src/cli/analysis_stats.rs
+++ b/crates/rust-analyzer/src/cli/analysis_stats.rs
@@ -72,7 +72,7 @@ impl AnalysisStatsCmd {
             shuffle(&mut rng, &mut krates);
         }
         for krate in krates {
-            let module = krate.root_module(db).expect("crate without root module");
+            let module = krate.root_module(db);
             let file_id = module.definition_source(db).file_id;
             let file_id = file_id.original_file(db);
             let source_root = db.file_source_root(file_id);
diff --git a/crates/rust-analyzer/src/cli/diagnostics.rs b/crates/rust-analyzer/src/cli/diagnostics.rs
index 4ac8c8772..f17fc5dfe 100644
--- a/crates/rust-analyzer/src/cli/diagnostics.rs
+++ b/crates/rust-analyzer/src/cli/diagnostics.rs
@@ -28,7 +28,7 @@ pub fn diagnostics(
     let mut work = Vec::new();
     let krates = Crate::all(db);
     for krate in krates {
-        let module = krate.root_module(db).expect("crate without root module");
+        let module = krate.root_module(db);
         let file_id = module.definition_source(db).file_id;
         let file_id = file_id.original_file(db);
         let source_root = db.file_source_root(file_id);