Fix goto def not working when cursor was over the name of a def

We now allow goto_definition to return the named NavigationTarget if the cursor
is on the name of a definition.

crates/ra_ide_api/src/goto_definition.rs

@@ -1,7 +1,8 @@
 use ra_db::{FileId, SourceDatabase};
 use ra_syntax::{
-    AstNode, ast,
-    algo::find_node_at_offset,
+    AstNode, ast::{self, NameOwner},
+    algo::{find_node_at_offset, visit::{visitor, Visitor}},
+    SyntaxNode,
 };
 use test_utils::tested_by;
 use hir::Resolution;
@@ -114,7 +115,9 @@ fn name_definition(
     file_id: FileId,
     name: &ast::Name,
 ) -> Option<Vec<NavigationTarget>> {
-    if let Some(module) = name.syntax().parent().and_then(ast::Module::cast) {
+    let parent = name.syntax().parent()?;
+
+    if let Some(module) = ast::Module::cast(&parent) {
         if module.has_semi() {
             if let Some(child_module) =
                 hir::source_binder::module_from_declaration(db, file_id, module)
@@ -124,9 +127,33 @@ fn name_definition(
             }
         }
     }
+
+    if let Some(nav) = named_target(file_id, &parent) {
+        return Some(vec![nav]);
+    }
+
     None
 }
 
+fn named_target(file_id: FileId, node: &SyntaxNode) -> Option<NavigationTarget> {
+    fn to_nav_target<N: NameOwner>(node: &N, file_id: FileId) -> Option<NavigationTarget> {
+        Some(NavigationTarget::from_named(file_id, node))
+    }
+
+    visitor()
+        .visit(|n: &ast::StructDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::EnumDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::EnumVariant| to_nav_target(n, file_id))
+        .visit(|n: &ast::FnDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::TypeDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::ConstDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::StaticDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::TraitDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::NamedFieldDef| to_nav_target(n, file_id))
+        .visit(|n: &ast::Module| to_nav_target(n, file_id))
+        .accept(node)?
+}
+
 #[cfg(test)]
 mod tests {
     use test_utils::covers;
@@ -231,4 +258,98 @@ mod tests {
             "spam NAMED_FIELD_DEF FileId(1) [17; 26) [17; 21)",
         );
     }
+
+    #[test]
+    fn goto_definition_works_when_used_on_definition_name_itself() {
+        check_goto(
+            "
+            //- /lib.rs
+            struct Foo<|> { value: u32 }
+            ",
+            "Foo STRUCT_DEF FileId(1) [0; 25) [7; 10)",
+        );
+
+        check_goto(
+            r#"
+            //- /lib.rs
+            struct Foo {
+                field<|>: string,
+            }
+            "#,
+            "field NAMED_FIELD_DEF FileId(1) [17; 30) [17; 22)",
+        );
+
+        check_goto(
+            "
+            //- /lib.rs
+            fn foo_test<|>() {
+            }
+            ",
+            "foo_test FN_DEF FileId(1) [0; 17) [3; 11)",
+        );
+
+        check_goto(
+            "
+            //- /lib.rs
+            enum Foo<|> {
+                Variant,
+            }
+            ",
+            "Foo ENUM_DEF FileId(1) [0; 25) [5; 8)",
+        );
+
+        check_goto(
+            "
+            //- /lib.rs
+            enum Foo {
+                Variant1,
+                Variant2<|>,
+                Variant3,
+            }
+            ",
+            "Variant2 ENUM_VARIANT FileId(1) [29; 37) [29; 37)",
+        );
+
+        check_goto(
+            r#"
+            //- /lib.rs
+            static inner<|>: &str = "";
+            "#,
+            "inner STATIC_DEF FileId(1) [0; 24) [7; 12)",
+        );
+
+        check_goto(
+            r#"
+            //- /lib.rs
+            const inner<|>: &str = "";
+            "#,
+            "inner CONST_DEF FileId(1) [0; 23) [6; 11)",
+        );
+
+        check_goto(
+            r#"
+            //- /lib.rs
+            type Thing<|> = Option<()>;
+            "#,
+            "Thing TYPE_DEF FileId(1) [0; 24) [5; 10)",
+        );
+
+        check_goto(
+            r#"
+            //- /lib.rs
+            trait Foo<|> {
+            }
+            "#,
+            "Foo TRAIT_DEF FileId(1) [0; 13) [6; 9)",
+        );
+
+        check_goto(
+            r#"
+            //- /lib.rs
+            mod bar<|> {
+            }
+            "#,
+            "bar MODULE FileId(1) [0; 11) [4; 7)",
+        );
+    }
 }

crates/ra_ide_api/src/navigation_target.rs

@@ -198,7 +198,8 @@ impl NavigationTarget {
         buf
     }
 
-    fn from_named(file_id: FileId, node: &impl ast::NameOwner) -> NavigationTarget {
+    /// Allows `NavigationTarget` to be created from a `NameOwner`
+    pub(crate) fn from_named(file_id: FileId, node: &impl ast::NameOwner) -> NavigationTarget {
         let name = node.name().map(|it| it.text().clone()).unwrap_or_default();
         let focus_range = node.name().map(|it| it.syntax().range());
         NavigationTarget::from_syntax(file_id, name, focus_range, node.syntax())