Parse trait alias as a distinct AST type

crates/hir-def/src/item_tree/lower.rs

@@ -110,6 +110,7 @@ impl<'a> Ctx<'a> {
             ast::Item::Const(ast) => self.lower_const(ast).into(),
             ast::Item::Module(ast) => self.lower_module(ast)?.into(),
             ast::Item::Trait(ast) => self.lower_trait(ast)?.into(),
+            ast::Item::TraitAlias(_) => return None,
             ast::Item::Impl(ast) => self.lower_impl(ast)?.into(),
             ast::Item::Use(ast) => self.lower_use(ast)?.into(),
             ast::Item::ExternCrate(ast) => self.lower_extern_crate(ast)?.into(),

crates/parser/src/grammar/items/traits.rs

@@ -20,7 +20,7 @@ pub(super) fn trait_(p: &mut Parser<'_>, m: Marker) {
         // trait Z<U> = where Self: T<U>;
         generic_params::opt_where_clause(p);
         p.expect(T![;]);
-        m.complete(p, TRAIT);
+        m.complete(p, TRAIT_ALIAS);
         return;
     }
 

crates/parser/src/syntax_kind/generated.rs

@@ -135,6 +135,7 @@ pub enum SyntaxKind {
     STATIC,
     CONST,
     TRAIT,
+    TRAIT_ALIAS,
     IMPL,
     TYPE_ALIAS,
     MACRO_CALL,

crates/parser/test_data/parser/inline/ok/0151_trait_alias.rast

@@ -1,5 +1,5 @@
 SOURCE_FILE
-  TRAIT
+  TRAIT_ALIAS
     TRAIT_KW "trait"
     WHITESPACE " "
     NAME

crates/parser/test_data/parser/inline/ok/0177_trait_alias_where_clause.rast

@@ -1,5 +1,5 @@
 SOURCE_FILE
-  TRAIT
+  TRAIT_ALIAS
     TRAIT_KW "trait"
     WHITESPACE " "
     NAME
@@ -50,7 +50,7 @@ SOURCE_FILE
                     IDENT "Copy"
     SEMICOLON ";"
   WHITESPACE "\n"
-  TRAIT
+  TRAIT_ALIAS
     TRAIT_KW "trait"
     WHITESPACE " "
     NAME

crates/syntax/rust.ungram

@@ -97,6 +97,7 @@ Item =
 | Static
 | Struct
 | Trait
+| TraitAlias
 | TypeAlias
 | Union
 | Use
@@ -240,10 +241,11 @@ Trait =
   Attr* Visibility?
   'unsafe'? 'auto'?
   'trait' Name GenericParamList?
-  (
+  (':' TypeBoundList?)? WhereClause? AssocItemList
-    (':' TypeBoundList?)? WhereClause? AssocItemList
+
-    | '=' TypeBoundList? WhereClause? ';'
+TraitAlias =
-  )
+  Attr* Visibility?
+  'trait' Name GenericParamList? '=' TypeBoundList? WhereClause? ';'
 
 AssocItemList =
   '{' Attr* AssocItem* '}'

crates/syntax/src/ast.rs

@@ -25,7 +25,8 @@ pub use self::{
     generated::{nodes::*, tokens::*},
     node_ext::{
         AttrKind, FieldKind, Macro, NameLike, NameOrNameRef, PathSegmentKind, SelfParamKind,
-        SlicePatComponents, StructKind, TypeBoundKind, TypeOrConstParam, VisibilityKind,
+        SlicePatComponents, StructKind, TraitOrAlias, TypeBoundKind, TypeOrConstParam,
+        VisibilityKind,
     },
     operators::{ArithOp, BinaryOp, CmpOp, LogicOp, Ordering, RangeOp, UnaryOp},
     token_ext::{CommentKind, CommentPlacement, CommentShape, IsString, QuoteOffsets, Radix},

crates/syntax/src/ast/generated/nodes.rs

@@ -407,7 +407,21 @@ impl Trait {
     pub fn auto_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![auto]) }
     pub fn trait_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![trait]) }
     pub fn assoc_item_list(&self) -> Option<AssocItemList> { support::child(&self.syntax) }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct TraitAlias {
+    pub(crate) syntax: SyntaxNode,
+}
+impl ast::HasAttrs for TraitAlias {}
+impl ast::HasName for TraitAlias {}
+impl ast::HasVisibility for TraitAlias {}
+impl ast::HasGenericParams for TraitAlias {}
+impl ast::HasDocComments for TraitAlias {}
+impl TraitAlias {
+    pub fn trait_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![trait]) }
     pub fn eq_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![=]) }
+    pub fn type_bound_list(&self) -> Option<TypeBoundList> { support::child(&self.syntax) }
     pub fn semicolon_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![;]) }
 }
 
@@ -1573,6 +1587,7 @@ pub enum Item {
     Static(Static),
     Struct(Struct),
     Trait(Trait),
+    TraitAlias(TraitAlias),
     TypeAlias(TypeAlias),
     Union(Union),
     Use(Use),
@@ -2058,6 +2073,17 @@ impl AstNode for Trait {
     }
     fn syntax(&self) -> &SyntaxNode { &self.syntax }
 }
+impl AstNode for TraitAlias {
+    fn can_cast(kind: SyntaxKind) -> bool { kind == TRAIT_ALIAS }
+    fn cast(syntax: SyntaxNode) -> Option<Self> {
+        if Self::can_cast(syntax.kind()) {
+            Some(Self { syntax })
+        } else {
+            None
+        }
+    }
+    fn syntax(&self) -> &SyntaxNode { &self.syntax }
+}
 impl AstNode for TypeAlias {
     fn can_cast(kind: SyntaxKind) -> bool { kind == TYPE_ALIAS }
     fn cast(syntax: SyntaxNode) -> Option<Self> {
@@ -3570,6 +3596,9 @@ impl From<Struct> for Item {
 impl From<Trait> for Item {
     fn from(node: Trait) -> Item { Item::Trait(node) }
 }
+impl From<TraitAlias> for Item {
+    fn from(node: TraitAlias) -> Item { Item::TraitAlias(node) }
+}
 impl From<TypeAlias> for Item {
     fn from(node: TypeAlias) -> Item { Item::TypeAlias(node) }
 }
@@ -3596,6 +3625,7 @@ impl AstNode for Item {
                 | STATIC
                 | STRUCT
                 | TRAIT
+                | TRAIT_ALIAS
                 | TYPE_ALIAS
                 | UNION
                 | USE
@@ -3616,6 +3646,7 @@ impl AstNode for Item {
             STATIC => Item::Static(Static { syntax }),
             STRUCT => Item::Struct(Struct { syntax }),
             TRAIT => Item::Trait(Trait { syntax }),
+            TRAIT_ALIAS => Item::TraitAlias(TraitAlias { syntax }),
             TYPE_ALIAS => Item::TypeAlias(TypeAlias { syntax }),
             UNION => Item::Union(Union { syntax }),
             USE => Item::Use(Use { syntax }),
@@ -3638,6 +3669,7 @@ impl AstNode for Item {
             Item::Static(it) => &it.syntax,
             Item::Struct(it) => &it.syntax,
             Item::Trait(it) => &it.syntax,
+            Item::TraitAlias(it) => &it.syntax,
             Item::TypeAlias(it) => &it.syntax,
             Item::Union(it) => &it.syntax,
             Item::Use(it) => &it.syntax,
@@ -3950,6 +3982,7 @@ impl AstNode for AnyHasAttrs {
                 | STATIC
                 | STRUCT
                 | TRAIT
+                | TRAIT_ALIAS
                 | TYPE_ALIAS
                 | UNION
                 | USE
@@ -4035,6 +4068,7 @@ impl AstNode for AnyHasDocComments {
                 | STATIC
                 | STRUCT
                 | TRAIT
+                | TRAIT_ALIAS
                 | TYPE_ALIAS
                 | UNION
                 | USE
@@ -4056,7 +4090,7 @@ impl AnyHasGenericParams {
 }
 impl AstNode for AnyHasGenericParams {
     fn can_cast(kind: SyntaxKind) -> bool {
-        matches!(kind, ENUM | FN | IMPL | STRUCT | TRAIT | TYPE_ALIAS | UNION)
+        matches!(kind, ENUM | FN | IMPL | STRUCT | TRAIT | TRAIT_ALIAS | TYPE_ALIAS | UNION)
     }
     fn cast(syntax: SyntaxNode) -> Option<Self> {
         Self::can_cast(syntax.kind()).then_some(AnyHasGenericParams { syntax })
@@ -4108,6 +4142,7 @@ impl AstNode for AnyHasName {
                 | STATIC
                 | STRUCT
                 | TRAIT
+                | TRAIT_ALIAS
                 | TYPE_ALIAS
                 | UNION
                 | RENAME
@@ -4163,6 +4198,7 @@ impl AstNode for AnyHasVisibility {
                 | STATIC
                 | STRUCT
                 | TRAIT
+                | TRAIT_ALIAS
                 | TYPE_ALIAS
                 | UNION
                 | USE
@@ -4391,6 +4427,11 @@ impl std::fmt::Display for Trait {
         std::fmt::Display::fmt(self.syntax(), f)
     }
 }
+impl std::fmt::Display for TraitAlias {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(self.syntax(), f)
+    }
+}
 impl std::fmt::Display for TypeAlias {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         std::fmt::Display::fmt(self.syntax(), f)

crates/syntax/src/ast/node_ext.rs

@@ -680,6 +680,51 @@ impl TypeOrConstParam {
     }
 }
 
+#[derive(Debug, Clone)]
+pub enum TraitOrAlias {
+    Trait(ast::Trait),
+    TraitAlias(ast::TraitAlias),
+}
+
+impl TraitOrAlias {
+    pub fn name(&self) -> Option<ast::Name> {
+        match self {
+            TraitOrAlias::Trait(x) => x.name(),
+            TraitOrAlias::TraitAlias(x) => x.name(),
+        }
+    }
+}
+
+impl AstNode for TraitOrAlias {
+    fn can_cast(kind: SyntaxKind) -> bool
+    where
+        Self: Sized,
+    {
+        matches!(kind, SyntaxKind::TRAIT | SyntaxKind::TRAIT_ALIAS)
+    }
+
+    fn cast(syntax: SyntaxNode) -> Option<Self>
+    where
+        Self: Sized,
+    {
+        let res = match syntax.kind() {
+            SyntaxKind::TRAIT => TraitOrAlias::Trait(ast::Trait { syntax }),
+            SyntaxKind::TRAIT_ALIAS => TraitOrAlias::TraitAlias(ast::TraitAlias { syntax }),
+            _ => return None,
+        };
+        Some(res)
+    }
+
+    fn syntax(&self) -> &SyntaxNode {
+        match self {
+            TraitOrAlias::Trait(it) => it.syntax(),
+            TraitOrAlias::TraitAlias(it) => it.syntax(),
+        }
+    }
+}
+
+impl HasAttrs for TraitOrAlias {}
+
 pub enum VisibilityKind {
     In(ast::Path),
     PubCrate,

crates/syntax/src/tests/ast_src.rs

@@ -86,6 +86,7 @@ pub(crate) const KINDS_SRC: KindsSrc<'_> = KindsSrc {
         "STATIC",
         "CONST",
         "TRAIT",
+        "TRAIT_ALIAS",
         "IMPL",
         "TYPE_ALIAS",
         "MACRO_CALL",

crates/syntax/src/tests/sourcegen_ast.rs

@@ -783,6 +783,7 @@ fn extract_struct_traits(ast: &mut AstSrc) {
         "Enum",
         "Variant",
         "Trait",
+        "TraitAlias",
         "Module",
         "Static",
         "Const",