Allow rest parameter trailing commas in ambient contexts (microsoft#23139)

Andy · web-flow · commit 6286c7577df8 · 2018-04-04T11:33:29.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -26662,7 +26662,9 @@ namespace ts {
                     if (i !== (parameterCount - 1)) {
                         return grammarErrorOnNode(parameter.dotDotDotToken, Diagnostics.A_rest_parameter_must_be_last_in_a_parameter_list);
                     }
-                    checkGrammarForDisallowedTrailingComma(parameters, Diagnostics.A_rest_parameter_or_binding_pattern_may_not_have_a_trailing_comma);
+                    if (!(parameter.flags & NodeFlags.Ambient)) { // Allow `...foo,` in ambient declarations; see GH#23070
+                        checkGrammarForDisallowedTrailingComma(parameters, Diagnostics.A_rest_parameter_or_binding_pattern_may_not_have_a_trailing_comma);
+                    }
 
                     if (isBindingPattern(parameter.name)) {
                         return grammarErrorOnNode(parameter.name, Diagnostics.A_rest_element_cannot_contain_a_binding_pattern);
diff --git a/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.errors.txt b/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.errors.txt
@@ -10,6 +10,9 @@ tests/cases/conformance/es7/trailingCommasInFunctionParametersAndArguments.ts(5,
                        ~
 !!! error TS1013: A rest parameter or binding pattern may not have a trailing comma.
     
+    // Allowed for ambient declarations
+    declare function f25(...args,): void;
+    
     f2(...[],);
     
     // Not confused by overloads
diff --git a/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.js b/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.js
@@ -5,6 +5,9 @@ f1(1,);
 
 function f2(...args,) {}
 
+// Allowed for ambient declarations
+declare function f25(...args,): void;
+
 f2(...[],);
 
 // Not confused by overloads
diff --git a/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.symbols b/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.symbols
@@ -10,47 +10,52 @@ function f2(...args,) {}
 >f2 : Symbol(f2, Decl(trailingCommasInFunctionParametersAndArguments.ts, 2, 7))
 >args : Symbol(args, Decl(trailingCommasInFunctionParametersAndArguments.ts, 4, 12))
 
+// Allowed for ambient declarations
+declare function f25(...args,): void;
+>f25 : Symbol(f25, Decl(trailingCommasInFunctionParametersAndArguments.ts, 4, 24))
+>args : Symbol(args, Decl(trailingCommasInFunctionParametersAndArguments.ts, 7, 21))
+
 f2(...[],);
 >f2 : Symbol(f2, Decl(trailingCommasInFunctionParametersAndArguments.ts, 2, 7))
 
 // Not confused by overloads
 declare function f3(x, ): number;
->f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 6, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 33))
->x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 20))
+>f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 12, 33))
+>x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 12, 20))
 
 declare function f3(x, y,): string;
->f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 6, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 33))
->x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 10, 20))
->y : Symbol(y, Decl(trailingCommasInFunctionParametersAndArguments.ts, 10, 22))
+>f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 12, 33))
+>x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 13, 20))
+>y : Symbol(y, Decl(trailingCommasInFunctionParametersAndArguments.ts, 13, 22))
 
 <number>f3(1,);
->f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 6, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 33))
+>f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 12, 33))
 
 <string>f3(1, 2,);
->f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 6, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 33))
+>f3 : Symbol(f3, Decl(trailingCommasInFunctionParametersAndArguments.ts, 9, 11), Decl(trailingCommasInFunctionParametersAndArguments.ts, 12, 33))
 
 // Works for constructors too
 class X {
->X : Symbol(X, Decl(trailingCommasInFunctionParametersAndArguments.ts, 13, 18))
+>X : Symbol(X, Decl(trailingCommasInFunctionParametersAndArguments.ts, 16, 18))
 
     constructor(a,) { }
->a : Symbol(a, Decl(trailingCommasInFunctionParametersAndArguments.ts, 17, 16))
+>a : Symbol(a, Decl(trailingCommasInFunctionParametersAndArguments.ts, 20, 16))
 
     // See trailingCommasInGetter.ts
     set x(value,) { }
->x : Symbol(X.x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 17, 23))
->value : Symbol(value, Decl(trailingCommasInFunctionParametersAndArguments.ts, 19, 10))
+>x : Symbol(X.x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 20, 23))
+>value : Symbol(value, Decl(trailingCommasInFunctionParametersAndArguments.ts, 22, 10))
 }
 interface Y {
->Y : Symbol(Y, Decl(trailingCommasInFunctionParametersAndArguments.ts, 20, 1))
+>Y : Symbol(Y, Decl(trailingCommasInFunctionParametersAndArguments.ts, 23, 1))
 
     new(x,);
->x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 22, 8))
+>x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 25, 8))
 
     (x,);
->x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 23, 5))
+>x : Symbol(x, Decl(trailingCommasInFunctionParametersAndArguments.ts, 26, 5))
 }
 
 new X(1,);
->X : Symbol(X, Decl(trailingCommasInFunctionParametersAndArguments.ts, 13, 18))
+>X : Symbol(X, Decl(trailingCommasInFunctionParametersAndArguments.ts, 16, 18))
 
diff --git a/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.types b/tests/baselines/reference/trailingCommasInFunctionParametersAndArguments.types
@@ -12,6 +12,11 @@ function f2(...args,) {}
 >f2 : (...args: any[]) => void
 >args : any[]
 
+// Allowed for ambient declarations
+declare function f25(...args,): void;
+>f25 : (...args: any[]) => void
+>args : any[]
+
 f2(...[],);
 >f2(...[],) : void
 >f2 : (...args: any[]) => void
diff --git a/tests/cases/conformance/es7/trailingCommasInFunctionParametersAndArguments.ts b/tests/cases/conformance/es7/trailingCommasInFunctionParametersAndArguments.ts
@@ -6,6 +6,9 @@ f1(1,);
 
 function f2(...args,) {}
 
+// Allowed for ambient declarations
+declare function f25(...args,): void;
+
 f2(...[],);
 
 // Not confused by overloads

Original file line number	Diff line number	Diff line change
`@@ -10,6 +10,9 @@ tests/cases/conformance/es7/trailingCommasInFunctionParametersAndArguments.ts(5,`
`10`	`10`	`~`
`11`	`11`	`!!! error TS1013: A rest parameter or binding pattern may not have a trailing comma.`
`12`	`12`
	`13`	`+ // Allowed for ambient declarations`
	`14`	`+ declare function f25(...args,): void;`
	`15`	`+`
`13`	`16`	`f2(...[],);`
`14`	`17`
`15`	`18`	`// Not confused by overloads`