Merge pull request microsoft#30699 from andrewbranch/bug/30635

Fix ternaries where "true" is a parenthesized variable and "false" is a function expression

Author: andrewbranch

src/compiler/parser.ts

@@ -3693,9 +3693,11 @@ namespace ts {
             //  - "(x = 10)" is an assignment expression parsed as a signature with a default parameter value.
             //  - "(x,y)" is a comma expression parsed as a signature with two parameters.
             //  - "a ? (b): c" will have "(b):" parsed as a signature with a return type annotation.
+            //  - "a ? (b): function() {}" will too, since function() is a valid JSDoc function type.
             //
             // So we need just a bit of lookahead to ensure that it can only be a signature.
-            if (!allowAmbiguity && token() !== SyntaxKind.EqualsGreaterThanToken && token() !== SyntaxKind.OpenBraceToken) {
+            const hasJSDocFunctionType = node.type && isJSDocFunctionType(node.type);
+            if (!allowAmbiguity && token() !== SyntaxKind.EqualsGreaterThanToken && (hasJSDocFunctionType || token() !== SyntaxKind.OpenBraceToken)) {
                 // Returning undefined here will cause our caller to rewind to where we started from.
                 return undefined;
             }

tests/baselines/reference/parserParenthesizedVariableAndFunctionInTernary.js

@@ -0,0 +1,8 @@
+//// [parserParenthesizedVariableAndFunctionInTernary.ts]
+let a: any;
+const c = true ? (a) : function() {};
+
+
+//// [parserParenthesizedVariableAndFunctionInTernary.js]
+var a;
+var c = true ? (a) : function () { };

tests/baselines/reference/parserParenthesizedVariableAndFunctionInTernary.symbols

@@ -0,0 +1,8 @@
+=== tests/cases/conformance/parser/ecmascript5/parserParenthesizedVariableAndFunctionInTernary.ts ===
+let a: any;
+>a : Symbol(a, Decl(parserParenthesizedVariableAndFunctionInTernary.ts, 0, 3))
+
+const c = true ? (a) : function() {};
+>c : Symbol(c, Decl(parserParenthesizedVariableAndFunctionInTernary.ts, 1, 5))
+>a : Symbol(a, Decl(parserParenthesizedVariableAndFunctionInTernary.ts, 0, 3))
+

tests/baselines/reference/parserParenthesizedVariableAndFunctionInTernary.types

@@ -0,0 +1,12 @@
+=== tests/cases/conformance/parser/ecmascript5/parserParenthesizedVariableAndFunctionInTernary.ts ===
+let a: any;
+>a : any
+
+const c = true ? (a) : function() {};
+>c : any
+>true ? (a) : function() {} : any
+>true : true
+>(a) : any
+>a : any
+>function() {} : () => void
+

tests/cases/conformance/parser/ecmascript5/parserParenthesizedVariableAndFunctionInTernary.ts

@@ -0,0 +1,2 @@
+let a: any;
+const c = true ? (a) : function() {};