Improve/fix type bound lowering

crates/ra_hir/src/ty/tests.rs

@@ -3415,6 +3415,39 @@ fn test(x: Trait, y: &Trait) -> u64 {
     );
 }
 
+#[test]
+fn weird_bounds() {
+    assert_snapshot_matches!(
+        infer(r#"
+trait Trait {}
+fn test() {
+    let a: impl Trait + 'lifetime = foo;
+    let b: impl 'lifetime = foo;
+    let b: impl (Trait) = foo;
+    let b: impl ('lifetime) = foo;
+    let d: impl ?Sized = foo;
+    let e: impl Trait + ?Sized = foo;
+}
+"#),
+        @r###"
+   ⋮
+   ⋮[26; 237) '{     ...foo; }': ()
+   ⋮[36; 37) 'a': impl Trait + {error}
+   ⋮[64; 67) 'foo': impl Trait + {error}
+   ⋮[77; 78) 'b': impl {error}
+   ⋮[97; 100) 'foo': impl {error}
+   ⋮[110; 111) 'b': impl Trait
+   ⋮[128; 131) 'foo': impl Trait
+   ⋮[141; 142) 'b': impl {error}
+   ⋮[163; 166) 'foo': impl {error}
+   ⋮[176; 177) 'd': impl {error}
+   ⋮[193; 196) 'foo': impl {error}
+   ⋮[206; 207) 'e': impl Trait + {error}
+   ⋮[231; 234) 'foo': impl Trait + {error}
+    "###
+    );
+}
+
 fn type_at_pos(db: &MockDatabase, pos: FilePosition) -> String {
     let file = db.parse(pos.file_id).ok().unwrap();
     let expr = algo::find_node_at_offset::<ast::Expr>(file.syntax(), pos.offset).unwrap();

crates/ra_hir/src/type_ref.rs

@@ -136,7 +136,7 @@ pub(crate) fn type_bounds_from_ast(type_bounds_opt: Option<ast::TypeBoundList>)
 impl TypeBound {
     pub(crate) fn from_ast(node: ast::TypeBound) -> Self {
         match node.kind() {
-            Some(ast::TypeBoundKind::PathType(path_type)) => {
+            ast::TypeBoundKind::PathType(path_type) => {
                 let path = match path_type.path() {
                     Some(p) => p,
                     None => return TypeBound::Error,
@@ -147,9 +147,7 @@ impl TypeBound {
                 };
                 TypeBound::Path(path)
             }
-            Some(ast::TypeBoundKind::ForType(_)) | Some(ast::TypeBoundKind::Lifetime(_)) | None => {
-                TypeBound::Error
-            }
+            ast::TypeBoundKind::ForType(_) | ast::TypeBoundKind::Lifetime(_) => TypeBound::Error,
         }
     }
 }

crates/ra_syntax/src/ast/extensions.rs

@@ -382,7 +382,36 @@ impl ast::WherePred {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum TypeBoundKind {
+    /// Trait
+    PathType(ast::PathType),
+    /// for<'a> ...
+    ForType(ast::ForType),
+    /// 'a
+    Lifetime(ast::SyntaxToken),
+}
+
 impl ast::TypeBound {
+    pub fn kind(&self) -> TypeBoundKind {
+        if let Some(path_type) = children(self).next() {
+            TypeBoundKind::PathType(path_type)
+        } else if let Some(for_type) = children(self).next() {
+            TypeBoundKind::ForType(for_type)
+        } else if let Some(lifetime) = self.lifetime() {
+            TypeBoundKind::Lifetime(lifetime)
+        } else {
+            unreachable!()
+        }
+    }
+
+    fn lifetime(&self) -> Option<SyntaxToken> {
+        self.syntax()
+            .children_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == LIFETIME)
+    }
+
     pub fn question_mark_token(&self) -> Option<SyntaxToken> {
         self.syntax()
             .children_with_tokens()
@@ -399,29 +428,3 @@ impl ast::TraitDef {
         self.syntax().children_with_tokens().any(|t| t.kind() == T![auto])
     }
 }
-
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub enum TypeBoundKind {
-    /// Trait
-    PathType(ast::PathType),
-    /// for<'a> ...
-    ForType(ast::ForType),
-    /// 'a
-    Lifetime(ast::SyntaxToken),
-}
-
-impl ast::TypeBound {
-    pub fn kind(&self) -> Option<TypeBoundKind> {
-        let child = self.syntax.first_child_or_token()?;
-        match child.kind() {
-            PATH_TYPE => Some(TypeBoundKind::PathType(
-                ast::PathType::cast(child.into_node().unwrap()).unwrap(),
-            )),
-            FOR_TYPE => Some(TypeBoundKind::ForType(
-                ast::ForType::cast(child.into_node().unwrap()).unwrap(),
-            )),
-            LIFETIME => Some(TypeBoundKind::Lifetime(child.into_token().unwrap())),
-            _ => unreachable!(),
-        }
-    }
-}