Merge pull request #20934 from Veykril/veykril/push-qtzmsqkzntpo

fix: Improve error recovery when parsing malformed function return types

Author: Veykril

crates/parser/src/grammar/expressions/atom.rs

@@ -588,6 +588,12 @@ fn closure_expr(p: &mut Parser<'_>) -> CompletedMarker {
     }
     params::param_list_closure(p);
     if opt_ret_type(p) {
+        // test_err closure_ret_recovery
+        // fn foo() { || -> A> { let x = 1; } }
+        while p.at(T![>]) {
+            // recover from unbalanced return type brackets
+            p.err_and_bump("expected a curly brace");
+        }
         // test lambda_ret_block
         // fn main() { || -> i32 { 92 }(); }
         block_expr(p);

crates/parser/src/grammar/items.rs

@@ -424,6 +424,14 @@ fn fn_(p: &mut Parser<'_>, m: Marker) {
     // fn bar() -> () {}
     opt_ret_type(p);
 
+    // test_err fn_ret_recovery
+    // fn foo() -> A>]) { let x = 1; }
+    // fn foo() -> A>]) where T: Copy { let x = 1; }
+    while p.at(T![')']) | p.at(T![']']) | p.at(T![>]) {
+        // recover from unbalanced return type brackets
+        p.err_and_bump("expected a curly brace");
+    }
+
     // test function_where_clause
     // fn foo<T>() where T: Copy {}
     generic_params::opt_where_clause(p);

crates/parser/test_data/generated/runner.rs

@@ -749,6 +749,10 @@ mod err {
     #[test]
     fn bad_asm_expr() { run_and_expect_errors("test_data/parser/inline/err/bad_asm_expr.rs"); }
     #[test]
+    fn closure_ret_recovery() {
+        run_and_expect_errors("test_data/parser/inline/err/closure_ret_recovery.rs");
+    }
+    #[test]
     fn comma_after_default_values_syntax() {
         run_and_expect_errors("test_data/parser/inline/err/comma_after_default_values_syntax.rs");
     }
@@ -773,6 +777,10 @@ mod err {
         run_and_expect_errors("test_data/parser/inline/err/fn_pointer_type_missing_fn.rs");
     }
     #[test]
+    fn fn_ret_recovery() {
+        run_and_expect_errors("test_data/parser/inline/err/fn_ret_recovery.rs");
+    }
+    #[test]
     fn gen_fn() {
         run_and_expect_errors_with_edition(
             "test_data/parser/inline/err/gen_fn.rs",

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

@@ -0,0 +1,52 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE " "
+        CLOSURE_EXPR
+          PARAM_LIST
+            PIPE "|"
+            PIPE "|"
+          WHITESPACE " "
+          RET_TYPE
+            THIN_ARROW "->"
+            WHITESPACE " "
+            PATH_TYPE
+              PATH
+                PATH_SEGMENT
+                  NAME_REF
+                    IDENT "A"
+          ERROR
+            R_ANGLE ">"
+          WHITESPACE " "
+          BLOCK_EXPR
+            STMT_LIST
+              L_CURLY "{"
+              WHITESPACE " "
+              LET_STMT
+                LET_KW "let"
+                WHITESPACE " "
+                IDENT_PAT
+                  NAME
+                    IDENT "x"
+                WHITESPACE " "
+                EQ "="
+                WHITESPACE " "
+                LITERAL
+                  INT_NUMBER "1"
+                SEMICOLON ";"
+              WHITESPACE " "
+              R_CURLY "}"
+        WHITESPACE " "
+        R_CURLY "}"
+  WHITESPACE "\n"
+error 18: expected a curly brace

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

@@ -0,0 +1 @@
+fn foo() { || -> A> { let x = 1; } }

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

@@ -0,0 +1,112 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    RET_TYPE
+      THIN_ARROW "->"
+      WHITESPACE " "
+      PATH_TYPE
+        PATH
+          PATH_SEGMENT
+            NAME_REF
+              IDENT "A"
+    ERROR
+      R_ANGLE ">"
+    ERROR
+      R_BRACK "]"
+    ERROR
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE " "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          IDENT_PAT
+            NAME
+              IDENT "x"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          LITERAL
+            INT_NUMBER "1"
+          SEMICOLON ";"
+        WHITESPACE " "
+        R_CURLY "}"
+  WHITESPACE "\n"
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    RET_TYPE
+      THIN_ARROW "->"
+      WHITESPACE " "
+      PATH_TYPE
+        PATH
+          PATH_SEGMENT
+            NAME_REF
+              IDENT "A"
+    ERROR
+      R_ANGLE ">"
+    ERROR
+      R_BRACK "]"
+    ERROR
+      R_PAREN ")"
+    WHITESPACE " "
+    WHERE_CLAUSE
+      WHERE_KW "where"
+      WHITESPACE " "
+      WHERE_PRED
+        PATH_TYPE
+          PATH
+            PATH_SEGMENT
+              NAME_REF
+                IDENT "T"
+        COLON ":"
+        WHITESPACE " "
+        TYPE_BOUND_LIST
+          TYPE_BOUND
+            PATH_TYPE
+              PATH
+                PATH_SEGMENT
+                  NAME_REF
+                    IDENT "Copy"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE " "
+        LET_STMT
+          LET_KW "let"
+          WHITESPACE " "
+          IDENT_PAT
+            NAME
+              IDENT "x"
+          WHITESPACE " "
+          EQ "="
+          WHITESPACE " "
+          LITERAL
+            INT_NUMBER "1"
+          SEMICOLON ";"
+        WHITESPACE " "
+        R_CURLY "}"
+  WHITESPACE "\n"
+error 13: expected a curly brace
+error 14: expected a curly brace
+error 15: expected a curly brace
+error 45: expected a curly brace
+error 46: expected a curly brace
+error 47: expected a curly brace

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

@@ -0,0 +1,2 @@
+fn foo() -> A>]) { let x = 1; }
+fn foo() -> A>]) where T: Copy { let x = 1; }