Demo: make colon always terminate in conditional expression on true side

src/compiler/parser.ts

@@ -4369,7 +4369,7 @@ namespace ts {
             }
 
             // It wasn't an assignment or a lambda.  This is a conditional expression:
-            return parseConditionalExpressionRest(expr, pos);
+            return parseConditionalExpressionRest(expr, pos, disallowReturnTypeInArrowFunction);
         }
 
         function isYieldExpression(): boolean {
@@ -4463,7 +4463,7 @@ namespace ts {
             // it out, but don't allow any ambiguity, and return 'undefined' if this could be an
             // expression instead.
             return triState === Tristate.True ?
-                parseParenthesizedArrowFunctionExpression(/*allowAmbiguity*/ true, /*disallowReturnTypeInArrowFunction*/ false) :
+                parseParenthesizedArrowFunctionExpression(/*allowAmbiguity*/ true, disallowReturnTypeInArrowFunction) :
                 tryParse(() => parsePossibleParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction));
         }
 
@@ -4702,13 +4702,8 @@ namespace ts {
             // This is a valid arrow function with "z" as the return type.
             //
             // But, if we're in the true side of a conditional expression, this colon
-            // terminates the expression, so we cannot allow a return type if we aren't
+            // terminates the expression, so we cannot allow a return type, even if we aren't
             // certain whether or not the preceding text was parsed as a parameter list.
-            //
-            // For example,
-            //     a() ? (b: number, c?: string): void => d() : e
-            // is determined by isParenthesizedArrowFunctionExpression to unambiguously
-            // be an arrow expression, so we allow a return type.
             if (disallowReturnTypeInArrowFunction && token() === SyntaxKind.ColonToken) {
                 return undefined;
             }
@@ -4788,7 +4783,7 @@ namespace ts {
             return node;
         }
 
-        function parseConditionalExpressionRest(leftOperand: Expression, pos: number): Expression {
+        function parseConditionalExpressionRest(leftOperand: Expression, pos: number, disallowReturnTypeInArrowFunction: boolean): Expression {
             // Note: we are passed in an expression which was produced from parseBinaryExpressionOrHigher.
             const questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
             if (!questionToken) {
@@ -4805,7 +4800,7 @@ namespace ts {
                     doOutsideOfContext(disallowInAndDecoratorContext, () => parseAssignmentExpressionOrHigher(/*disallowReturnTypeInArrowFunction*/ true)),
                     colonToken = parseExpectedToken(SyntaxKind.ColonToken),
                     nodeIsPresent(colonToken)
-                        ? parseAssignmentExpressionOrHigher(/*disallowReturnTypeInArrowFunction*/ true)
+                        ? parseAssignmentExpressionOrHigher(disallowReturnTypeInArrowFunction) // inherit disallowReturnTypeInArrowFunction in false side
                         : createMissingNode(SyntaxKind.Identifier, /*reportAtCurrentPosition*/ false, Diagnostics._0_expected, tokenToString(SyntaxKind.ColonToken))
                 ),
                 pos

tests/baselines/reference/parserArrowFunctionExpression10.errors.txt

@@ -1,20 +1,17 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,1): error TS2304: Cannot find name 'a'.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,6): error TS2304: Cannot find name 'b'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,17): error TS2304: Cannot find name 'd'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,20): error TS1005: ';' expected.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,22): error TS2304: Cannot find name 'e'.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,27): error TS2304: Cannot find name 'f'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts (5 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts (4 errors) ====
     a ? (b) : c => (d) : e => f
     ~
 !!! error TS2304: Cannot find name 'a'.
          ~
 !!! error TS2304: Cannot find name 'b'.
-                    ~
-!!! error TS2304: Cannot find name 'd'.
-                       ~
-!!! error TS1005: ';' expected.
+                         ~
+!!! error TS2304: Cannot find name 'e'.
                               ~
 !!! error TS2304: Cannot find name 'f'.
 

tests/baselines/reference/parserArrowFunctionExpression10.js

@@ -3,5 +3,4 @@ a ? (b) : c => (d) : e => f
 
 
 //// [parserArrowFunctionExpression10.js]
-a ? (b) : function (c) { return (d); };
-(function (e) { return f; });
+a ? (b) : function (c) { return function (d) { return f; }; };

tests/baselines/reference/parserArrowFunctionExpression10.symbols

@@ -1,5 +1,6 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts ===
 a ? (b) : c => (d) : e => f
 >c : Symbol(c, Decl(parserArrowFunctionExpression10.ts, 0, 9))
->e : Symbol(e, Decl(parserArrowFunctionExpression10.ts, 0, 20))
+>d : Symbol(d, Decl(parserArrowFunctionExpression10.ts, 0, 16))
+>e : Symbol(e)
 

tests/baselines/reference/parserArrowFunctionExpression10.types

@@ -1,14 +1,12 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts ===
 a ? (b) : c => (d) : e => f
->a ? (b) : c => (d) : any
+>a ? (b) : c => (d) : e => f : any
 >a : any
 >(b) : any
 >b : any
->c => (d) : (c: any) => any
+>c => (d) : e => f : (c: any) => (d: any) => e
 >c : any
->(d) : any
+>(d) : e => f : (d: any) => e
 >d : any
->e => f : (e: any) => any
->e : any
 >f : any
 

tests/baselines/reference/parserArrowFunctionExpression14.errors.txt

@@ -1,14 +1,23 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,1): error TS2304: Cannot find name 'a'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,30): error TS1109: Expression expected.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,37): error TS1109: Expression expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,40): error TS2304: Cannot find name 'd'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,44): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,46): error TS2304: Cannot find name 'e'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts (3 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts (6 errors) ====
     a() ? (b: number, c?: string): void => d() : e;
     ~
 !!! error TS2304: Cannot find name 'a'.
+                                 ~
+!!! error TS1109: Expression expected.
+                                        ~~
+!!! error TS1109: Expression expected.
                                            ~
 !!! error TS2304: Cannot find name 'd'.
+                                               ~
+!!! error TS1005: ';' expected.
                                                  ~
 !!! error TS2304: Cannot find name 'e'.
 

tests/baselines/reference/parserArrowFunctionExpression14.js

@@ -3,4 +3,6 @@ a() ? (b: number, c?: string): void => d() : e;
 
 
 //// [parserArrowFunctionExpression14.js]
-a() ? function (b, c) { return d(); } : e;
+a() ?  : void ;
+d();
+e;

tests/baselines/reference/parserArrowFunctionExpression14.symbols

@@ -1,5 +1,4 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts ===
 a() ? (b: number, c?: string): void => d() : e;
->b : Symbol(b, Decl(parserArrowFunctionExpression14.ts, 0, 7))
->c : Symbol(c, Decl(parserArrowFunctionExpression14.ts, 0, 17))
-
+No type information for this code.
+No type information for this code.

tests/baselines/reference/parserArrowFunctionExpression14.types

@@ -1,11 +1,11 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts ===
 a() ? (b: number, c?: string): void => d() : e;
->a() ? (b: number, c?: string): void => d() : e : any
+>a() ? (b: number, c?: string): void : any
 >a() : any
 >a : any
->(b: number, c?: string): void => d() : (b: number, c?: string) => void
->b : number
->c : string
+> : any
+>void : undefined
+> : any
 >d() : any
 >d : any
 >e : any

tests/baselines/reference/parserArrowFunctionExpression15.errors.txt

@@ -0,0 +1,14 @@
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,10): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,28): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,34): error TS1005: ';' expected.
+
+
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts (3 errors) ====
+    false ? (param): string => param : null
+             ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                               ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                     ~
+!!! error TS1005: ';' expected.
+

tests/baselines/reference/parserArrowFunctionExpression15.js

@@ -0,0 +1,7 @@
+//// [parserArrowFunctionExpression15.ts]
+false ? (param): string => param : null
+
+
+//// [parserArrowFunctionExpression15.js]
+false ? (param) : function (string) { return param; };
+null;

tests/baselines/reference/parserArrowFunctionExpression15.symbols

@@ -0,0 +1,4 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
+false ? (param): string => param : null
+>string : Symbol(string, Decl(parserArrowFunctionExpression15.ts, 0, 16))
+

tests/baselines/reference/parserArrowFunctionExpression15.types

@@ -0,0 +1,11 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
+false ? (param): string => param : null
+>false ? (param): string => param : any
+>false : false
+>(param) : any
+>param : any
+>string => param : (string: any) => any
+>string : any
+>param : any
+>null : null
+

tests/baselines/reference/parserArrowFunctionExpression16.errors.txt

@@ -0,0 +1,14 @@
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,17): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,35): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,48): error TS1005: ';' expected.
+
+
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts (3 errors) ====
+    true ? false ? (param): string => param : null : null
+                    ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                      ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                                   ~
+!!! error TS1005: ';' expected.
+

tests/baselines/reference/parserArrowFunctionExpression16.js

@@ -0,0 +1,7 @@
+//// [parserArrowFunctionExpression16.ts]
+true ? false ? (param): string => param : null : null
+
+
+//// [parserArrowFunctionExpression16.js]
+true ? false ? (param) : function (string) { return param; } : null;
+null;

tests/baselines/reference/parserArrowFunctionExpression16.symbols

@@ -0,0 +1,4 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
+true ? false ? (param): string => param : null : null
+>string : Symbol(string, Decl(parserArrowFunctionExpression16.ts, 0, 23))
+

tests/baselines/reference/parserArrowFunctionExpression16.types

@@ -0,0 +1,14 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
+true ? false ? (param): string => param : null : null
+>true ? false ? (param): string => param : null : any
+>true : true
+>false ? (param): string => param : any
+>false : false
+>(param) : any
+>param : any
+>string => param : (string: any) => any
+>string : any
+>param : any
+>null : null
+>null : null
+

tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts

@@ -0,0 +1 @@
+false ? (param): string => param : null

tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts

@@ -0,0 +1 @@
+true ? false ? (param): string => param : null : null