feat: Implement default-field-values only in parser

crates/parser/src/grammar/expressions.rs

@@ -678,6 +678,8 @@ fn path_expr(p: &mut Parser<'_>, r: Restrictions) -> (CompletedMarker, BlockLike
 //     S { x };
 //     S { x, y: 32, };
 //     S { x, y: 32, ..Default::default() };
+//     S { x, y: 32, .. };
+//     S { .. };
 //     S { x: ::default() };
 //     TupleStruct { 0: 1 };
 // }
@@ -709,6 +711,8 @@ pub(crate) fn record_expr_field_list(p: &mut Parser<'_>) {
                 // fn main() {
                 //     S { field ..S::default() }
                 //     S { 0 ..S::default() }
+                //     S { field .. }
+                //     S { 0 .. }
                 // }
                 name_ref_or_index(p);
                 p.error("expected `:`");
@@ -739,7 +743,13 @@ pub(crate) fn record_expr_field_list(p: &mut Parser<'_>) {
                 //     S { .. } = S {};
                 // }
 
-                // We permit `.. }` on the left-hand side of a destructuring assignment.
+                // test struct_initializer_with_defaults
+                // fn foo() {
+                //     let _s = S { .. };
+                // }
+
+                // We permit `.. }` on the left-hand side of a destructuring assignment
+                // or defaults values.
                 if !p.at(T!['}']) {
                     expr(p);
 
@@ -750,6 +760,12 @@ pub(crate) fn record_expr_field_list(p: &mut Parser<'_>) {
                         //     S { ..x, a: 0 }
                         // }
 
+                        // test_err comma_after_default_values_syntax
+                        // fn foo() {
+                        //     S { .., };
+                        //     S { .., a: 0 }
+                        // }
+
                         // Do not bump, so we can support additional fields after this comma.
                         p.error("cannot use a comma after the base struct");
                     }

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

@@ -135,6 +135,11 @@ pub(crate) fn record_field_list(p: &mut Parser<'_>) {
             name(p);
             p.expect(T![:]);
             types::type_(p);
+            // test record_field_default_values
+            // struct S { f: f32 = 0.0 }
+            if p.eat(T![=]) {
+                expressions::expr(p);
+            }
             m.complete(p, RECORD_FIELD);
         } else {
             m.abandon(p);

crates/parser/test_data/generated/runner.rs

@@ -482,6 +482,10 @@ mod ok {
         run_and_expect_no_errors("test_data/parser/inline/ok/record_field_attrs.rs");
     }
     #[test]
+    fn record_field_default_values() {
+        run_and_expect_no_errors("test_data/parser/inline/ok/record_field_default_values.rs");
+    }
+    #[test]
     fn record_field_list() {
         run_and_expect_no_errors("test_data/parser/inline/ok/record_field_list.rs");
     }
@@ -544,6 +548,10 @@ mod ok {
         run_and_expect_no_errors("test_data/parser/inline/ok/stmt_postfix_expr_ambiguity.rs");
     }
     #[test]
+    fn struct_initializer_with_defaults() {
+        run_and_expect_no_errors("test_data/parser/inline/ok/struct_initializer_with_defaults.rs");
+    }
+    #[test]
     fn struct_item() { run_and_expect_no_errors("test_data/parser/inline/ok/struct_item.rs"); }
     #[test]
     fn trait_alias() { run_and_expect_no_errors("test_data/parser/inline/ok/trait_alias.rs"); }
@@ -719,6 +727,10 @@ mod err {
         );
     }
     #[test]
+    fn comma_after_default_values_syntax() {
+        run_and_expect_errors("test_data/parser/inline/err/comma_after_default_values_syntax.rs");
+    }
+    #[test]
     fn crate_visibility_empty_recover() {
         run_and_expect_errors("test_data/parser/inline/err/crate_visibility_empty_recover.rs");
     }

crates/parser/test_data/parser/inline/err/comma_after_default_values_syntax.rast

@@ -0,0 +1,59 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              DOT2 ".."
+              ERROR
+                COMMA ","
+              WHITESPACE " "
+              R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
+        RECORD_EXPR
+          PATH
+            PATH_SEGMENT
+              NAME_REF
+                IDENT "S"
+          WHITESPACE " "
+          RECORD_EXPR_FIELD_LIST
+            L_CURLY "{"
+            WHITESPACE " "
+            DOT2 ".."
+            ERROR
+              COMMA ","
+            WHITESPACE " "
+            RECORD_EXPR_FIELD
+              NAME_REF
+                IDENT "a"
+              COLON ":"
+              WHITESPACE " "
+              LITERAL
+                INT_NUMBER "0"
+            WHITESPACE " "
+            R_CURLY "}"
+        WHITESPACE "\n"
+        R_CURLY "}"
+  WHITESPACE "\n"
+error 21: expected expression
+error 36: expected expression
+error 37: expected COMMA

crates/parser/test_data/parser/inline/err/comma_after_default_values_syntax.rs

@@ -0,0 +1,4 @@
+fn foo() {
+    S { .., };
+    S { .., a: 0 }
+}

crates/parser/test_data/parser/inline/err/record_literal_before_ellipsis_recovery.rast

@@ -44,6 +44,56 @@ SOURCE_FILE
               WHITESPACE " "
               R_CURLY "}"
         WHITESPACE "\n    "
+        EXPR_STMT
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              RECORD_EXPR_FIELD
+                NAME_REF
+                  INT_NUMBER "0"
+              WHITESPACE " "
+              DOT2 ".."
+              CALL_EXPR
+                PATH_EXPR
+                  PATH
+                    PATH
+                      PATH_SEGMENT
+                        NAME_REF
+                          IDENT "S"
+                    COLON2 "::"
+                    PATH_SEGMENT
+                      NAME_REF
+                        IDENT "default"
+                ARG_LIST
+                  L_PAREN "("
+                  R_PAREN ")"
+              WHITESPACE " "
+              R_CURLY "}"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              RECORD_EXPR_FIELD
+                NAME_REF
+                  IDENT "field"
+              WHITESPACE " "
+              DOT2 ".."
+              WHITESPACE " "
+              R_CURLY "}"
+        WHITESPACE "\n    "
         RECORD_EXPR
           PATH
             PATH_SEGMENT
@@ -58,20 +108,6 @@ SOURCE_FILE
                 INT_NUMBER "0"
             WHITESPACE " "
             DOT2 ".."
-            CALL_EXPR
-              PATH_EXPR
-                PATH
-                  PATH
-                    PATH_SEGMENT
-                      NAME_REF
-                        IDENT "S"
-                  COLON2 "::"
-                  PATH_SEGMENT
-                    NAME_REF
-                      IDENT "default"
-              ARG_LIST
-                L_PAREN "("
-                R_PAREN ")"
             WHITESPACE " "
             R_CURLY "}"
         WHITESPACE "\n"
@@ -82,3 +118,9 @@ error 25: expected COMMA
 error 42: expected SEMICOLON
 error 52: expected `:`
 error 52: expected COMMA
+error 69: expected SEMICOLON
+error 83: expected `:`
+error 83: expected COMMA
+error 88: expected SEMICOLON
+error 98: expected `:`
+error 98: expected COMMA

crates/parser/test_data/parser/inline/err/record_literal_before_ellipsis_recovery.rs

@@ -1,4 +1,6 @@
 fn main() {
     S { field ..S::default() }
     S { 0 ..S::default() }
+    S { field .. }
+    S { 0 .. }
 }

crates/parser/test_data/parser/inline/ok/record_field_default_values.rast

@@ -0,0 +1,28 @@
+SOURCE_FILE
+  STRUCT
+    STRUCT_KW "struct"
+    WHITESPACE " "
+    NAME
+      IDENT "S"
+    WHITESPACE " "
+    RECORD_FIELD_LIST
+      L_CURLY "{"
+      WHITESPACE " "
+      RECORD_FIELD
+        NAME
+          IDENT "f"
+        COLON ":"
+        WHITESPACE " "
+        PATH_TYPE
+          PATH
+            PATH_SEGMENT
+              NAME_REF
+                IDENT "f32"
+        WHITESPACE " "
+        EQ "="
+        WHITESPACE " "
+        LITERAL
+          FLOAT_NUMBER "0.0"
+      WHITESPACE " "
+      R_CURLY "}"
+  WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/record_field_default_values.rs

@@ -0,0 +1 @@
+struct S { f: f32 = 0.0 }

crates/parser/test_data/parser/inline/ok/record_lit.rast

@@ -120,6 +120,53 @@ SOURCE_FILE
               R_CURLY "}"
           SEMICOLON ";"
         WHITESPACE "\n    "
+        EXPR_STMT
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              RECORD_EXPR_FIELD
+                PATH_EXPR
+                  PATH
+                    PATH_SEGMENT
+                      NAME_REF
+                        IDENT "x"
+              COMMA ","
+              WHITESPACE " "
+              RECORD_EXPR_FIELD
+                NAME_REF
+                  IDENT "y"
+                COLON ":"
+                WHITESPACE " "
+                LITERAL
+                  INT_NUMBER "32"
+              COMMA ","
+              WHITESPACE " "
+              DOT2 ".."
+              WHITESPACE " "
+              R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              DOT2 ".."
+              WHITESPACE " "
+              R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n    "
         EXPR_STMT
           RECORD_EXPR
             PATH

crates/parser/test_data/parser/inline/ok/record_lit.rs

@@ -3,6 +3,8 @@ fn foo() {
     S { x };
     S { x, y: 32, };
     S { x, y: 32, ..Default::default() };
+    S { x, y: 32, .. };
+    S { .. };
     S { x: ::default() };
     TupleStruct { 0: 1 };
 }

crates/parser/test_data/parser/inline/ok/struct_initializer_with_defaults.rast

@@ -0,0 +1,39 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE "\n    "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          IDENT_PAT
+            NAME
+              IDENT "_s"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          RECORD_EXPR
+            PATH
+              PATH_SEGMENT
+                NAME_REF
+                  IDENT "S"
+            WHITESPACE " "
+            RECORD_EXPR_FIELD_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              DOT2 ".."
+              WHITESPACE " "
+              R_CURLY "}"
+          SEMICOLON ";"
+        WHITESPACE "\n"
+        R_CURLY "}"
+  WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/struct_initializer_with_defaults.rs

@@ -0,0 +1,3 @@
+fn foo() {
+    let _s = S { .. };
+}

crates/syntax/rust.ungram

@@ -241,7 +241,7 @@ RecordFieldList =
 
 RecordField =
   Attr* Visibility?
-  Name ':' Type
+  Name ':' Type ('=' Expr)?
 
 TupleFieldList =
   '(' fields:(TupleField (',' TupleField)* ','?)? ')'

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

@@ -1538,10 +1538,14 @@ impl ast::HasDocComments for RecordField {}
 impl ast::HasName for RecordField {}
 impl ast::HasVisibility for RecordField {}
 impl RecordField {
+    #[inline]
+    pub fn expr(&self) -> Option<Expr> { support::child(&self.syntax) }
     #[inline]
     pub fn ty(&self) -> Option<Type> { support::child(&self.syntax) }
     #[inline]
     pub fn colon_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![:]) }
+    #[inline]
+    pub fn eq_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![=]) }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]