Don't parse DotDotDotToken in JSX attribute values (#55284)

src/compiler/parser.ts

@@ -6214,7 +6214,9 @@ namespace Parser {
         let dotDotDotToken: DotDotDotToken | undefined;
         let expression: Expression | undefined;
         if (token() !== SyntaxKind.CloseBraceToken) {
-            dotDotDotToken = parseOptionalToken(SyntaxKind.DotDotDotToken);
+            if (!inExpressionContext) {
+                dotDotDotToken = parseOptionalToken(SyntaxKind.DotDotDotToken);
+            }
             // Only an AssignmentExpression is valid here per the JSX spec,
             // but we can unambiguously parse a comma sequence and provide
             // a better error message in grammar checking.

tests/baselines/reference/jsxParsingErrorImmediateSpreadInAttributeValue.errors.txt

@@ -0,0 +1,21 @@
+a.tsx(11,7): error TS1109: Expression expected.
+a.tsx(11,11): error TS1003: Identifier expected.
+
+
+==== a.tsx (2 errors) ====
+    declare const React: any
+    declare namespace JSX {
+        interface IntrinsicElements {
+            [k: string]: any
+        }
+    }
+    
+    const X: any
+    const a: any
+    
+    <X a={...a} />
+          ~~~
+!!! error TS1109: Expression expected.
+              ~
+!!! error TS1003: Identifier expected.
+    

tests/baselines/reference/jsxParsingErrorImmediateSpreadInAttributeValue.js

@@ -0,0 +1,20 @@
+//// [tests/cases/conformance/jsx/jsxParsingErrorImmediateSpreadInAttributeValue.tsx] ////
+
+//// [a.tsx]
+declare const React: any
+declare namespace JSX {
+    interface IntrinsicElements {
+        [k: string]: any
+    }
+}
+
+const X: any
+const a: any
+
+<X a={...a} />
+
+
+//// [a.js]
+var X;
+var a;
+React.createElement(X, { a: , a: true });

tests/baselines/reference/jsxParsingErrorImmediateSpreadInAttributeValue.symbols

@@ -0,0 +1,28 @@
+//// [tests/cases/conformance/jsx/jsxParsingErrorImmediateSpreadInAttributeValue.tsx] ////
+
+=== a.tsx ===
+declare const React: any
+>React : Symbol(React, Decl(a.tsx, 0, 13))
+
+declare namespace JSX {
+>JSX : Symbol(JSX, Decl(a.tsx, 0, 24))
+
+    interface IntrinsicElements {
+>IntrinsicElements : Symbol(IntrinsicElements, Decl(a.tsx, 1, 23))
+
+        [k: string]: any
+>k : Symbol(k, Decl(a.tsx, 3, 9))
+    }
+}
+
+const X: any
+>X : Symbol(X, Decl(a.tsx, 7, 5))
+
+const a: any
+>a : Symbol(a, Decl(a.tsx, 8, 5))
+
+<X a={...a} />
+>X : Symbol(X, Decl(a.tsx, 7, 5))
+>a : Symbol(a, Decl(a.tsx, 10, 2), Decl(a.tsx, 10, 9))
+>a : Symbol(a, Decl(a.tsx, 10, 2), Decl(a.tsx, 10, 9))
+

tests/baselines/reference/jsxParsingErrorImmediateSpreadInAttributeValue.types

@@ -0,0 +1,26 @@
+//// [tests/cases/conformance/jsx/jsxParsingErrorImmediateSpreadInAttributeValue.tsx] ////
+
+=== a.tsx ===
+declare const React: any
+>React : any
+
+declare namespace JSX {
+    interface IntrinsicElements {
+        [k: string]: any
+>k : string
+    }
+}
+
+const X: any
+>X : any
+
+const a: any
+>a : any
+
+<X a={...a} />
+><X a={...a} /> : any
+>X : any
+>a : any
+> : any
+>a : any
+

tests/cases/conformance/jsx/jsxParsingErrorImmediateSpreadInAttributeValue.tsx

@@ -0,0 +1,14 @@
+// @jsx: react
+// @filename: a.tsx
+
+declare const React: any
+declare namespace JSX {
+    interface IntrinsicElements {
+        [k: string]: any
+    }
+}
+
+const X: any
+const a: any
+
+<X a={...a} />