Merge pull request #27522 from jack-williams/trailing-void-args-are-o…

…ptional

Fix #4260 : Allow trailing arguments that accept void to be omitted

src/compiler/checker.ts

@@ -18816,6 +18816,10 @@ namespace ts {
             return findIndex(args, isSpreadArgument);
         }
 
+        function acceptsVoid(t: Type): boolean {
+            return !!(t.flags & TypeFlags.Void);
+        }
+
         function hasCorrectArity(node: CallLikeExpression, args: ReadonlyArray<Expression>, signature: Signature, signatureHelpTrailingComma = false) {
             let argCount: number;
             let callIsIncomplete = false; // In incomplete call we want to be lenient when we have too few arguments
@@ -18877,8 +18881,16 @@ namespace ts {
 
             // If the call is incomplete, we should skip the lower bound check.
             // JSX signatures can have extra parameters provided by the library which we don't check
-            const hasEnoughArguments = argCount >= effectiveMinimumArguments;
-            return callIsIncomplete || hasEnoughArguments;
+            if (callIsIncomplete || argCount >= effectiveMinimumArguments) {
+                return true;
+            }
+            for (let i = argCount; i < effectiveMinimumArguments; i++) {
+                const type = getTypeAtPosition(signature, i);
+                if (filterType(type, acceptsVoid).flags & TypeFlags.Never) {
+                    return false;
+                }
+            }
+            return true;
         }
 
         function hasCorrectTypeArgumentArity(signature: Signature, typeArguments: NodeArray<TypeNode> | undefined) {

tests/baselines/reference/callWithMissingVoid.errors.txt

@@ -0,0 +1,131 @@
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(16,1): error TS2554: Expected 1 arguments, but got 0.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(19,1): error TS2554: Expected 1 arguments, but got 0.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(22,1): error TS2554: Expected 1 arguments, but got 0.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(35,31): error TS2554: Expected 1 arguments, but got 0.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(36,35): error TS2554: Expected 1 arguments, but got 0.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(37,33): error TS2554: Expected 1 arguments, but got 0.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(48,1): error TS2554: Expected 3 arguments, but got 1.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(55,1): error TS2554: Expected 4 arguments, but got 2.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(56,1): error TS2554: Expected 4 arguments, but got 3.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(57,1): error TS2554: Expected 4 arguments, but got 1.
+tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts(75,1): error TS2554: Expected 3 arguments, but got 1.
+
+
+==== tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts (11 errors) ====
+    // From #4260
+    class X<T> {
+        f(t: T) {
+            return { a: t };
+        }
+    }
+
+    declare const x: X<void>;
+    x.f() // no error because f expects void
+
+    declare const xUnion: X<void | number>;
+    xUnion.f(42) // no error because f accepts number
+    xUnion.f() // no error because f accepts void
+
+    declare const xAny: X<any>;
+    xAny.f() // error, any still expects an argument
+    ~~~~~~~~
+!!! error TS2554: Expected 1 arguments, but got 0.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:3:7: An argument for 't' was not provided.
+
+    declare const xUnknown: X<unknown>;
+    xUnknown.f() // error, unknown still expects an argument
+    ~~~~~~~~~~~~
+!!! error TS2554: Expected 1 arguments, but got 0.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:3:7: An argument for 't' was not provided.
+
+    declare const xNever: X<never>;
+    xNever.f() // error, never still expects an argument
+    ~~~~~~~~~~
+!!! error TS2554: Expected 1 arguments, but got 0.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:3:7: An argument for 't' was not provided.
+
+
+    // Promise has previously been updated to work without arguments, but to show this fixes the issue too.
+
+    class MyPromise<X> {
+        constructor(executor: (resolve: (value: X) => void) => void) {
+
+        }
+    }
+
+    new MyPromise<void>(resolve => resolve()); // no error
+    new MyPromise<void | number>(resolve => resolve()); // no error
+    new MyPromise<any>(resolve => resolve()); // error, `any` arguments cannot be omitted
+                                  ~~~~~~~~~
+!!! error TS2554: Expected 1 arguments, but got 0.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:28:38: An argument for 'value' was not provided.
+    new MyPromise<unknown>(resolve => resolve()); // error, `unknown` arguments cannot be omitted
+                                      ~~~~~~~~~
+!!! error TS2554: Expected 1 arguments, but got 0.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:28:38: An argument for 'value' was not provided.
+    new MyPromise<never>(resolve => resolve()); // error, `never` arguments cannot be omitted
+                                    ~~~~~~~~~
+!!! error TS2554: Expected 1 arguments, but got 0.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:28:38: An argument for 'value' was not provided.
+
+
+    // Multiple parameters
+
+    function a(x: number, y: string, z: void): void  {
+
+    }
+
+    a(4, "hello"); // ok
+    a(4, "hello", void 0); // ok
+    a(4); // not ok
+    ~~~~
+!!! error TS2554: Expected 3 arguments, but got 1.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:42:23: An argument for 'y' was not provided.
+
+    function b(x: number, y: string, z: void, what: number): void  {
+
+    }
+
+    b(4, "hello", void 0, 2); // ok
+    b(4, "hello"); // not ok
+    ~~~~~~~~~~~~~
+!!! error TS2554: Expected 4 arguments, but got 2.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:50:34: An argument for 'z' was not provided.
+    b(4, "hello", void 0); // not ok
+    ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2554: Expected 4 arguments, but got 3.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:50:43: An argument for 'what' was not provided.
+    b(4); // not ok
+    ~~~~
+!!! error TS2554: Expected 4 arguments, but got 1.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:50:23: An argument for 'y' was not provided.
+
+    function c(x: number | void, y: void, z: void | string | number): void  {
+
+    }
+
+    c(3, void 0, void 0); // ok
+    c(3, void 0); // ok
+    c(3); // ok
+    c(); // ok
+
+
+    // Spread Parameters
+
+    declare function call<TS extends unknown[]>(
+        handler: (...args: TS) => unknown,
+        ...args: TS): void;
+
+    call((x: number, y: number) => x + y) // error
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2554: Expected 3 arguments, but got 1.
+!!! related TS6210 tests/cases/conformance/expressions/functionCalls/callWithMissingVoid.ts:73:5: An argument for 'args' was not provided.
+    call((x: number, y: number) => x + y, 4, 2) // ok
+
+    call((x: number, y: void) => x, 4, void 0) // ok
+    call((x: number, y: void) => x, 4) // ok
+    call((x: void, y: void) => 42) // ok
+    call((x: number | void, y: number | void) => 42) // ok
+    call((x: number | void, y: number | void) => 42, 4) // ok
+    call((x: number | void, y: number | void) => 42, 4, 2) // ok
+

tests/baselines/reference/callWithMissingVoid.js

@@ -0,0 +1,140 @@
+//// [callWithMissingVoid.ts]
+// From #4260
+class X<T> {
+    f(t: T) {
+        return { a: t };
+    }
+}
+
+declare const x: X<void>;
+x.f() // no error because f expects void
+
+declare const xUnion: X<void | number>;
+xUnion.f(42) // no error because f accepts number
+xUnion.f() // no error because f accepts void
+
+declare const xAny: X<any>;
+xAny.f() // error, any still expects an argument
+
+declare const xUnknown: X<unknown>;
+xUnknown.f() // error, unknown still expects an argument
+
+declare const xNever: X<never>;
+xNever.f() // error, never still expects an argument
+
+
+// Promise has previously been updated to work without arguments, but to show this fixes the issue too.
+
+class MyPromise<X> {
+    constructor(executor: (resolve: (value: X) => void) => void) {
+
+    }
+}
+
+new MyPromise<void>(resolve => resolve()); // no error
+new MyPromise<void | number>(resolve => resolve()); // no error
+new MyPromise<any>(resolve => resolve()); // error, `any` arguments cannot be omitted
+new MyPromise<unknown>(resolve => resolve()); // error, `unknown` arguments cannot be omitted
+new MyPromise<never>(resolve => resolve()); // error, `never` arguments cannot be omitted
+
+
+// Multiple parameters
+
+function a(x: number, y: string, z: void): void  {
+
+}
+
+a(4, "hello"); // ok
+a(4, "hello", void 0); // ok
+a(4); // not ok
+
+function b(x: number, y: string, z: void, what: number): void  {
+
+}
+
+b(4, "hello", void 0, 2); // ok
+b(4, "hello"); // not ok
+b(4, "hello", void 0); // not ok
+b(4); // not ok
+
+function c(x: number | void, y: void, z: void | string | number): void  {
+
+}
+
+c(3, void 0, void 0); // ok
+c(3, void 0); // ok
+c(3); // ok
+c(); // ok
+
+
+// Spread Parameters
+
+declare function call<TS extends unknown[]>(
+    handler: (...args: TS) => unknown,
+    ...args: TS): void;
+
+call((x: number, y: number) => x + y) // error
+call((x: number, y: number) => x + y, 4, 2) // ok
+
+call((x: number, y: void) => x, 4, void 0) // ok
+call((x: number, y: void) => x, 4) // ok
+call((x: void, y: void) => 42) // ok
+call((x: number | void, y: number | void) => 42) // ok
+call((x: number | void, y: number | void) => 42, 4) // ok
+call((x: number | void, y: number | void) => 42, 4, 2) // ok
+
+
+//// [callWithMissingVoid.js]
+"use strict";
+// From #4260
+var X = /** @class */ (function () {
+    function X() {
+    }
+    X.prototype.f = function (t) {
+        return { a: t };
+    };
+    return X;
+}());
+x.f(); // no error because f expects void
+xUnion.f(42); // no error because f accepts number
+xUnion.f(); // no error because f accepts void
+xAny.f(); // error, any still expects an argument
+xUnknown.f(); // error, unknown still expects an argument
+xNever.f(); // error, never still expects an argument
+// Promise has previously been updated to work without arguments, but to show this fixes the issue too.
+var MyPromise = /** @class */ (function () {
+    function MyPromise(executor) {
+    }
+    return MyPromise;
+}());
+new MyPromise(function (resolve) { return resolve(); }); // no error
+new MyPromise(function (resolve) { return resolve(); }); // no error
+new MyPromise(function (resolve) { return resolve(); }); // error, `any` arguments cannot be omitted
+new MyPromise(function (resolve) { return resolve(); }); // error, `unknown` arguments cannot be omitted
+new MyPromise(function (resolve) { return resolve(); }); // error, `never` arguments cannot be omitted
+// Multiple parameters
+function a(x, y, z) {
+}
+a(4, "hello"); // ok
+a(4, "hello", void 0); // ok
+a(4); // not ok
+function b(x, y, z, what) {
+}
+b(4, "hello", void 0, 2); // ok
+b(4, "hello"); // not ok
+b(4, "hello", void 0); // not ok
+b(4); // not ok
+function c(x, y, z) {
+}
+c(3, void 0, void 0); // ok
+c(3, void 0); // ok
+c(3); // ok
+c(); // ok
+call(function (x, y) { return x + y; }); // error
+call(function (x, y) { return x + y; }, 4, 2); // ok
+call(function (x, y) { return x; }, 4, void 0); // ok
+call(function (x, y) { return x; }, 4); // ok
+call(function (x, y) { return 42; }); // ok
+call(function (x, y) { return 42; }); // ok
+call(function (x, y) { return 42; }, 4); // ok
+call(function (x, y) { return 42; }, 4, 2); // ok