Less restrictive Parameters<T> and ReturnType<T>

src/lib/es5.d.ts

@@ -1451,22 +1451,22 @@ type NonNullable<T> = T extends null | undefined ? never : T;
 /**
  * Obtain the parameters of a function type in a tuple
  */
-type Parameters<T extends (...args: any[]) => any> = T extends (...args: infer P) => any ? P : never;
+type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : never;
 
 /**
  * Obtain the parameters of a constructor function type in a tuple
  */
-type ConstructorParameters<T extends new (...args: any[]) => any> = T extends new (...args: infer P) => any ? P : never;
+type ConstructorParameters<T extends new (...args: any) => any> = T extends new (...args: infer P) => any ? P : never;
 
 /**
  * Obtain the return type of a function type
  */
-type ReturnType<T extends (...args: any[]) => any> = T extends (...args: any[]) => infer R ? R : any;
+type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;
 
 /**
  * Obtain the return type of a constructor function type
  */
-type InstanceType<T extends new (...args: any[]) => any> = T extends new (...args: any[]) => infer R ? R : any;
+type InstanceType<T extends new (...args: any) => any> = T extends new (...args: any) => infer R ? R : any;
 
 /**
  * Marker for contextual 'this' type

tests/baselines/reference/genericRestParameters1.errors.txt

@@ -1,19 +1,13 @@
 tests/cases/conformance/types/rest/genericRestParameters1.ts(22,1): error TS2556: Expected 3 arguments, but got 1 or more.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(31,1): error TS2556: Expected 3 arguments, but got 1 or more.
-tests/cases/conformance/types/rest/genericRestParameters1.ts(133,40): error TS2344: Type '(...args: T) => void' does not satisfy the constraint '(...args: any[]) => any'.
-  Types of parameters 'args' and 'args' are incompatible.
-    Type 'any[]' is not assignable to type 'T'.
-tests/cases/conformance/types/rest/genericRestParameters1.ts(134,51): error TS2344: Type 'new (...args: T) => void' does not satisfy the constraint 'new (...args: any[]) => any'.
-  Types of parameters 'args' and 'args' are incompatible.
-    Type 'any[]' is not assignable to type 'T'.
-tests/cases/conformance/types/rest/genericRestParameters1.ts(135,23): error TS2344: Type 'Function' does not satisfy the constraint '(...args: any[]) => any'.
-  Type 'Function' provides no match for the signature '(...args: any[]): any'.
+tests/cases/conformance/types/rest/genericRestParameters1.ts(135,23): error TS2344: Type 'Function' does not satisfy the constraint '(...args: any) => any'.
+  Type 'Function' provides no match for the signature '(...args: any): any'.
 tests/cases/conformance/types/rest/genericRestParameters1.ts(164,1): error TS2322: Type '(a: never) => void' is not assignable to type '(...args: any[]) => void'.
   Types of parameters 'a' and 'args' are incompatible.
     Type 'any' is not assignable to type 'never'.
 
 
-==== tests/cases/conformance/types/rest/genericRestParameters1.ts (6 errors) ====
+==== tests/cases/conformance/types/rest/genericRestParameters1.ts (4 errors) ====
     declare let f1: (...x: [number, string, boolean]) => void;
     declare let f2: (x0: number, x1: string, x2: boolean) => void;
 
@@ -152,19 +146,11 @@ tests/cases/conformance/types/rest/genericRestParameters1.ts(164,1): error TS232
     type T05<T> = Parameters<(...args: T[]) => void>;
     type T06<T> = ConstructorParameters<new (...args: []) => void>;
     type T07<T extends any[]> = Parameters<(...args: T) => void>;
-                                           ~~~~~~~~~~~~~~~~~~~~
-!!! error TS2344: Type '(...args: T) => void' does not satisfy the constraint '(...args: any[]) => any'.
-!!! error TS2344:   Types of parameters 'args' and 'args' are incompatible.
-!!! error TS2344:     Type 'any[]' is not assignable to type 'T'.
     type T08<T extends any[]> = ConstructorParameters<new (...args: T) => void>;
-                                                      ~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2344: Type 'new (...args: T) => void' does not satisfy the constraint 'new (...args: any[]) => any'.
-!!! error TS2344:   Types of parameters 'args' and 'args' are incompatible.
-!!! error TS2344:     Type 'any[]' is not assignable to type 'T'.
     type T09 = Parameters<Function>;
                           ~~~~~~~~
-!!! error TS2344: Type 'Function' does not satisfy the constraint '(...args: any[]) => any'.
-!!! error TS2344:   Type 'Function' provides no match for the signature '(...args: any[]): any'.
+!!! error TS2344: Type 'Function' does not satisfy the constraint '(...args: any) => any'.
+!!! error TS2344:   Type 'Function' provides no match for the signature '(...args: any): any'.
 
     type Record1 = {
       move: [number, 'left' | 'right'];

tests/baselines/reference/inferTypes1.errors.txt

@@ -1,23 +1,23 @@
-tests/cases/conformance/types/conditional/inferTypes1.ts(31,23): error TS2344: Type 'string' does not satisfy the constraint '(...args: any[]) => any'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(32,23): error TS2344: Type 'Function' does not satisfy the constraint '(...args: any[]) => any'.
-  Type 'Function' provides no match for the signature '(...args: any[]): any'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(37,25): error TS2344: Type 'string' does not satisfy the constraint 'new (...args: any[]) => any'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(38,25): error TS2344: Type 'Function' does not satisfy the constraint 'new (...args: any[]) => any'.
-  Type 'Function' provides no match for the signature 'new (...args: any[]): any'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(46,25): error TS2344: Type '(x: string, y: string) => number' does not satisfy the constraint '(x: any) => any'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(47,25): error TS2344: Type 'Function' does not satisfy the constraint '(x: any) => any'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(31,23): error TS2344: Type 'string' does not satisfy the constraint '(...args: any) => any'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(32,23): error TS2344: Type 'Function' does not satisfy the constraint '(...args: any) => any'.
+  Type 'Function' provides no match for the signature '(...args: any): any'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(38,25): error TS2344: Type 'string' does not satisfy the constraint 'new (...args: any) => any'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(39,25): error TS2344: Type 'Function' does not satisfy the constraint 'new (...args: any) => any'.
+  Type 'Function' provides no match for the signature 'new (...args: any): any'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(47,25): error TS2344: Type '(x: string, y: string) => number' does not satisfy the constraint '(x: any) => any'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(48,25): error TS2344: Type 'Function' does not satisfy the constraint '(x: any) => any'.
   Type 'Function' provides no match for the signature '(x: any): any'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(73,12): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
-tests/cases/conformance/types/conditional/inferTypes1.ts(74,15): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
-tests/cases/conformance/types/conditional/inferTypes1.ts(74,41): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
-tests/cases/conformance/types/conditional/inferTypes1.ts(74,51): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
-tests/cases/conformance/types/conditional/inferTypes1.ts(75,15): error TS2304: Cannot find name 'U'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(75,15): error TS4081: Exported type alias 'T62' has or is using private name 'U'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(75,43): error TS2304: Cannot find name 'U'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(75,43): error TS4081: Exported type alias 'T62' has or is using private name 'U'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(82,44): error TS2344: Type 'U' does not satisfy the constraint 'string'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(74,12): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
+tests/cases/conformance/types/conditional/inferTypes1.ts(75,15): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
+tests/cases/conformance/types/conditional/inferTypes1.ts(75,41): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
+tests/cases/conformance/types/conditional/inferTypes1.ts(75,51): error TS1338: 'infer' declarations are only permitted in the 'extends' clause of a conditional type.
+tests/cases/conformance/types/conditional/inferTypes1.ts(76,15): error TS2304: Cannot find name 'U'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(76,15): error TS4081: Exported type alias 'T62' has or is using private name 'U'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(76,43): error TS2304: Cannot find name 'U'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(76,43): error TS4081: Exported type alias 'T62' has or is using private name 'U'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(83,44): error TS2344: Type 'U' does not satisfy the constraint 'string'.
   Type 'number' is not assignable to type 'string'.
-tests/cases/conformance/types/conditional/inferTypes1.ts(144,40): error TS2322: Type 'T' is not assignable to type 'string | number | symbol'.
+tests/cases/conformance/types/conditional/inferTypes1.ts(145,40): error TS2322: Type 'T' is not assignable to type 'string | number | symbol'.
   Type 'T' is not assignable to type 'symbol'.
 
 
@@ -54,22 +54,23 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(144,40): error TS2322:
     type T16 = ReturnType<never>;  // never
     type T17 = ReturnType<string>;  // Error
                           ~~~~~~
-!!! error TS2344: Type 'string' does not satisfy the constraint '(...args: any[]) => any'.
+!!! error TS2344: Type 'string' does not satisfy the constraint '(...args: any) => any'.
     type T18 = ReturnType<Function>;  // Error
                           ~~~~~~~~
-!!! error TS2344: Type 'Function' does not satisfy the constraint '(...args: any[]) => any'.
-!!! error TS2344:   Type 'Function' provides no match for the signature '(...args: any[]): any'.
+!!! error TS2344: Type 'Function' does not satisfy the constraint '(...args: any) => any'.
+!!! error TS2344:   Type 'Function' provides no match for the signature '(...args: any): any'.
+    type T19<T extends any[]> = ReturnType<(x: string, ...args: T) => T[]>;  // T[]
 
     type U10 = InstanceType<typeof C>;  // C
     type U11 = InstanceType<any>;  // any
     type U12 = InstanceType<never>;  // never
     type U13 = InstanceType<string>;  // Error
                             ~~~~~~
-!!! error TS2344: Type 'string' does not satisfy the constraint 'new (...args: any[]) => any'.
+!!! error TS2344: Type 'string' does not satisfy the constraint 'new (...args: any) => any'.
     type U14 = InstanceType<Function>;  // Error
                             ~~~~~~~~
-!!! error TS2344: Type 'Function' does not satisfy the constraint 'new (...args: any[]) => any'.
-!!! error TS2344:   Type 'Function' provides no match for the signature 'new (...args: any[]): any'.
+!!! error TS2344: Type 'Function' does not satisfy the constraint 'new (...args: any) => any'.
+!!! error TS2344:   Type 'Function' provides no match for the signature 'new (...args: any): any'.
 
     type ArgumentType<T extends (x: any) => any> = T extends (a: infer A) => any ? A : any;
 
@@ -226,4 +227,14 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(144,40): error TS2322:
 
     type Test1 = EnsureIsString<"hello">;  // "hello"
     type Test2 = EnsureIsString<42>;  // never
+
+    // Repros from #26856
+
+    function invoker <K extends string | number | symbol, A extends any[]> (key: K, ...args: A) {
+        return <T extends Record<K, (...args: A) => any>> (obj: T): ReturnType<T[K]> => obj[key](...args)
+    }
+
+    const result = invoker('test', true)({ test: (a: boolean) => 123 })
+
+    type Foo2<A extends any[]> = ReturnType<(...args: A) => string>;
 

tests/baselines/reference/inferTypes1.js

@@ -31,6 +31,7 @@ type T15 = ReturnType<any>;  // any
 type T16 = ReturnType<never>;  // never
 type T17 = ReturnType<string>;  // Error
 type T18 = ReturnType<Function>;  // Error
+type T19<T extends any[]> = ReturnType<(x: string, ...args: T) => T[]>;  // T[]
 
 type U10 = InstanceType<typeof C>;  // C
 type U11 = InstanceType<any>;  // any
@@ -166,6 +167,16 @@ type EnsureIsString<T> = T extends MustBeString<infer U> ? U : never;
 
 type Test1 = EnsureIsString<"hello">;  // "hello"
 type Test2 = EnsureIsString<42>;  // never
+
+// Repros from #26856
+
+function invoker <K extends string | number | symbol, A extends any[]> (key: K, ...args: A) {
+    return <T extends Record<K, (...args: A) => any>> (obj: T): ReturnType<T[K]> => obj[key](...args)
+}
+
+const result = invoker('test', true)({ test: (a: boolean) => 123 })
+
+type Foo2<A extends any[]> = ReturnType<(...args: A) => string>;
 
 
 //// [inferTypes1.js]
@@ -182,3 +193,12 @@ var C = /** @class */ (function () {
 }());
 var z1 = ex.customClass;
 var z2 = ex.obj.nested.attr;
+// Repros from #26856
+function invoker(key) {
+    var args = [];
+    for (var _i = 1; _i < arguments.length; _i++) {
+        args[_i - 1] = arguments[_i];
+    }
+    return function (obj) { return obj[key].apply(obj, args); };
+}
+var result = invoker('test', true)({ test: function (a) { return 123; } });