Array.prototype.concat definition improvement

src/lib/es5.d.ts

@@ -1070,7 +1070,7 @@ interface ReadonlyArray<T> {
       * Combines two or more arrays.
       * @param items Additional items to add to the end of array1.
       */
-    concat(...items: ConcatArray<T>[]): T[];
+    concat<U>(...items: (ConcatArray<T> | ConcatArray<U>)[]): (T | U)[];
     /**
       * Combines two or more arrays.
       * @param items Additional items to add to the end of array1.
@@ -1198,7 +1198,7 @@ interface Array<T> {
       * Combines two or more arrays.
       * @param items Additional items to add to the end of array1.
       */
-    concat(...items: ConcatArray<T>[]): T[];
+    concat<U>(...items: (ConcatArray<T> | ConcatArray<U>)[]): (T | U)[];
     /**
       * Combines two or more arrays.
       * @param items Additional items to add to the end of array1.

tests/baselines/reference/arrayConcat2.types

@@ -5,17 +5,17 @@ var a: string[] = [];
 
 a.concat("hello", 'world');
 >a.concat("hello", 'world') : string[]
->a.concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>a.concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >a : string[]
->concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >"hello" : "hello"
 >'world' : "world"
 
 a.concat('Hello');
 >a.concat('Hello') : string[]
->a.concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>a.concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >a : string[]
->concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >'Hello' : "Hello"
 
 var b = new Array<string>();
@@ -25,8 +25,8 @@ var b = new Array<string>();
 
 b.concat('hello');
 >b.concat('hello') : string[]
->b.concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>b.concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >b : string[]
->concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >'hello' : "hello"
 

tests/baselines/reference/arrayConcat3.types

@@ -10,10 +10,10 @@ function doStuff<T extends object, T1 extends T>(a: Array<Fn<T>>, b: Array<Fn<T1
 >b : Fn<T1>[]
 
     b.concat(a);
->b.concat(a) : Fn<T1>[]
->b.concat : { (...items: ConcatArray<Fn<T1>>[]): Fn<T1>[]; (...items: (Fn<T1> | ConcatArray<Fn<T1>>)[]): Fn<T1>[]; }
+>b.concat(a) : (Fn<T> | Fn<T1>)[]
+>b.concat : { <U>(...items: (ConcatArray<Fn<T1>> | ConcatArray<U>)[]): (Fn<T1> | U)[]; (...items: (Fn<T1> | ConcatArray<Fn<T1>>)[]): Fn<T1>[]; }
 >b : Fn<T1>[]
->concat : { (...items: ConcatArray<Fn<T1>>[]): Fn<T1>[]; (...items: (Fn<T1> | ConcatArray<Fn<T1>>)[]): Fn<T1>[]; }
+>concat : { <U>(...items: (ConcatArray<Fn<T1>> | ConcatArray<U>)[]): (Fn<T1> | U)[]; (...items: (Fn<T1> | ConcatArray<Fn<T1>>)[]): Fn<T1>[]; }
 >a : Fn<T>[]
 }
 

tests/baselines/reference/arrayConcatMap.types

@@ -4,9 +4,9 @@ var x = [].concat([{ a: 1 }], [{ a: 2 }])
 >[].concat([{ a: 1 }], [{ a: 2 }])          .map(b => b.a) : any[]
 >[].concat([{ a: 1 }], [{ a: 2 }])          .map : <U>(callbackfn: (value: any, index: number, array: any[]) => U, thisArg?: any) => U[]
 >[].concat([{ a: 1 }], [{ a: 2 }]) : any[]
->[].concat : { (...items: ConcatArray<any>[]): any[]; (...items: any[]): any[]; }
+>[].concat : { <U>(...items: (ConcatArray<any> | ConcatArray<U>)[]): any[]; (...items: any[]): any[]; }
 >[] : undefined[]
->concat : { (...items: ConcatArray<any>[]): any[]; (...items: any[]): any[]; }
+>concat : { <U>(...items: (ConcatArray<any> | ConcatArray<U>)[]): any[]; (...items: any[]): any[]; }
 >[{ a: 1 }] : { a: number; }[]
 >{ a: 1 } : { a: number; }
 >a : number

tests/baselines/reference/arrayOfSubtypeIsAssignableToReadonlyArray.errors.txt

@@ -3,9 +3,12 @@ tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(13,1): error T
     Property 'b' is missing in type 'A'.
 tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(18,1): error TS2322: Type 'C<A>' is not assignable to type 'ReadonlyArray<B>'.
   Types of property 'concat' are incompatible.
-    Type '{ (...items: ConcatArray<A>[]): A[]; (...items: (A | ConcatArray<A>)[]): A[]; }' is not assignable to type '{ (...items: ConcatArray<B>[]): B[]; (...items: (B | ConcatArray<B>)[]): B[]; }'.
-      Type 'A[]' is not assignable to type 'B[]'.
-        Type 'A' is not assignable to type 'B'.
+    Type '{ <U>(...items: (ConcatArray<A> | ConcatArray<U>)[]): (A | U)[]; (...items: (A | ConcatArray<A>)[]): A[]; }' is not assignable to type '{ <U>(...items: (ConcatArray<B> | ConcatArray<U>)[]): (B | U)[]; (...items: (B | ConcatArray<B>)[]): B[]; }'.
+      Types of parameters 'items' and 'items' are incompatible.
+        Type 'B | ConcatArray<B>' is not assignable to type 'ConcatArray<any> | ConcatArray<A>'.
+          Type 'B' is not assignable to type 'ConcatArray<any> | ConcatArray<A>'.
+            Type 'B' is not assignable to type 'ConcatArray<A>'.
+              Property 'length' is missing in type 'B'.
 
 
 ==== tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts (2 errors) ====
@@ -34,7 +37,10 @@ tests/cases/compiler/arrayOfSubtypeIsAssignableToReadonlyArray.ts(18,1): error T
     ~~~
 !!! error TS2322: Type 'C<A>' is not assignable to type 'ReadonlyArray<B>'.
 !!! error TS2322:   Types of property 'concat' are incompatible.
-!!! error TS2322:     Type '{ (...items: ConcatArray<A>[]): A[]; (...items: (A | ConcatArray<A>)[]): A[]; }' is not assignable to type '{ (...items: ConcatArray<B>[]): B[]; (...items: (B | ConcatArray<B>)[]): B[]; }'.
-!!! error TS2322:       Type 'A[]' is not assignable to type 'B[]'.
-!!! error TS2322:         Type 'A' is not assignable to type 'B'.
+!!! error TS2322:     Type '{ <U>(...items: (ConcatArray<A> | ConcatArray<U>)[]): (A | U)[]; (...items: (A | ConcatArray<A>)[]): A[]; }' is not assignable to type '{ <U>(...items: (ConcatArray<B> | ConcatArray<U>)[]): (B | U)[]; (...items: (B | ConcatArray<B>)[]): B[]; }'.
+!!! error TS2322:       Types of parameters 'items' and 'items' are incompatible.
+!!! error TS2322:         Type 'B | ConcatArray<B>' is not assignable to type 'ConcatArray<any> | ConcatArray<A>'.
+!!! error TS2322:           Type 'B' is not assignable to type 'ConcatArray<any> | ConcatArray<A>'.
+!!! error TS2322:             Type 'B' is not assignable to type 'ConcatArray<A>'.
+!!! error TS2322:               Property 'length' is missing in type 'B'.
 

tests/baselines/reference/concatError.types

@@ -15,19 +15,19 @@ fa = fa.concat([0]);
 >fa = fa.concat([0]) : number[]
 >fa : number[]
 >fa.concat([0]) : number[]
->fa.concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>fa.concat : { <U>(...items: (ConcatArray<number> | ConcatArray<U>)[]): (number | U)[]; (...items: (number | ConcatArray<number>)[]): number[]; }
 >fa : number[]
->concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>concat : { <U>(...items: (ConcatArray<number> | ConcatArray<U>)[]): (number | U)[]; (...items: (number | ConcatArray<number>)[]): number[]; }
 >[0] : number[]
 >0 : 0
 
 fa = fa.concat(0);
 >fa = fa.concat(0) : number[]
 >fa : number[]
 >fa.concat(0) : number[]
->fa.concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>fa.concat : { <U>(...items: (ConcatArray<number> | ConcatArray<U>)[]): (number | U)[]; (...items: (number | ConcatArray<number>)[]): number[]; }
 >fa : number[]
->concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>concat : { <U>(...items: (ConcatArray<number> | ConcatArray<U>)[]): (number | U)[]; (...items: (number | ConcatArray<number>)[]): number[]; }
 >0 : 0
 
 

tests/baselines/reference/concatTuples.types

@@ -10,9 +10,9 @@ ijs = ijs.concat([[3, 4], [5, 6]]);
 >ijs = ijs.concat([[3, 4], [5, 6]]) : [number, number][]
 >ijs : [number, number][]
 >ijs.concat([[3, 4], [5, 6]]) : [number, number][]
->ijs.concat : { (...items: ConcatArray<[number, number]>[]): [number, number][]; (...items: ([number, number] | ConcatArray<[number, number]>)[]): [number, number][]; }
+>ijs.concat : { <U>(...items: (ConcatArray<[number, number]> | ConcatArray<U>)[]): ([number, number] | U)[]; (...items: ([number, number] | ConcatArray<[number, number]>)[]): [number, number][]; }
 >ijs : [number, number][]
->concat : { (...items: ConcatArray<[number, number]>[]): [number, number][]; (...items: ([number, number] | ConcatArray<[number, number]>)[]): [number, number][]; }
+>concat : { <U>(...items: (ConcatArray<[number, number]> | ConcatArray<U>)[]): ([number, number] | U)[]; (...items: ([number, number] | ConcatArray<[number, number]>)[]): [number, number][]; }
 >[[3, 4], [5, 6]] : [number, number][]
 >[3, 4] : [number, number]
 >3 : 3

tests/baselines/reference/contextualExpressionTypecheckingDoesntBlowStack.types

@@ -72,12 +72,12 @@ export default class Operation {
 >result = (result || []).concat(innerResult) : IValidationError[]
 >result : IValidationError[] | null
 >(result || []).concat(innerResult) : IValidationError[]
->(result || []).concat : { (...items: ConcatArray<IValidationError>[]): IValidationError[]; (...items: (IValidationError | ConcatArray<IValidationError>)[]): IValidationError[]; }
+>(result || []).concat : { <U>(...items: (ConcatArray<IValidationError> | ConcatArray<U>)[]): (IValidationError | U)[]; (...items: (IValidationError | ConcatArray<IValidationError>)[]): IValidationError[]; }
 >(result || []) : IValidationError[]
 >result || [] : IValidationError[]
 >result : IValidationError[] | null
 >[] : never[]
->concat : { (...items: ConcatArray<IValidationError>[]): IValidationError[]; (...items: (IValidationError | ConcatArray<IValidationError>)[]): IValidationError[]; }
+>concat : { <U>(...items: (ConcatArray<IValidationError> | ConcatArray<U>)[]): (IValidationError | U)[]; (...items: (IValidationError | ConcatArray<IValidationError>)[]): IValidationError[]; }
 >innerResult : any
             }
         }

tests/baselines/reference/emitSkipsThisWithRestParameter.types

@@ -18,10 +18,10 @@ function rebase(fn: (base: any, ...args: any[]) => any): (...args: any[]) => any
 >apply : (this: Function, thisArg: any, argArray?: any) => any
 >this : any
 >[ this ].concat(args) : any[]
->[ this ].concat : { (...items: ConcatArray<any>[]): any[]; (...items: any[]): any[]; }
+>[ this ].concat : { <U>(...items: (ConcatArray<any> | ConcatArray<U>)[]): any[]; (...items: any[]): any[]; }
 >[ this ] : any[]
 >this : any
->concat : { (...items: ConcatArray<any>[]): any[]; (...items: any[]): any[]; }
+>concat : { <U>(...items: (ConcatArray<any> | ConcatArray<U>)[]): any[]; (...items: any[]): any[]; }
 >args : any[]
 
     };

tests/baselines/reference/intersectionTypeInference3.types

@@ -24,13 +24,13 @@ declare const b: Set<A>;
 const c1 = Array.from(a).concat(Array.from(b));
 >c1 : Nominal<"A", string>[]
 >Array.from(a).concat(Array.from(b)) : Nominal<"A", string>[]
->Array.from(a).concat : { (...items: ConcatArray<Nominal<"A", string>>[]): Nominal<"A", string>[]; (...items: (Nominal<"A", string> | ConcatArray<Nominal<"A", string>>)[]): Nominal<"A", string>[]; }
+>Array.from(a).concat : { <U>(...items: (ConcatArray<Nominal<"A", string>> | ConcatArray<U>)[]): (Nominal<"A", string> | U)[]; (...items: (Nominal<"A", string> | ConcatArray<Nominal<"A", string>>)[]): Nominal<"A", string>[]; }
 >Array.from(a) : Nominal<"A", string>[]
 >Array.from : { <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(iterable: Iterable<T> | ArrayLike<T>): T[]; <T, U>(iterable: Iterable<T> | ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
 >Array : ArrayConstructor
 >from : { <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(iterable: Iterable<T> | ArrayLike<T>): T[]; <T, U>(iterable: Iterable<T> | ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
 >a : Set<Nominal<"A", string>>
->concat : { (...items: ConcatArray<Nominal<"A", string>>[]): Nominal<"A", string>[]; (...items: (Nominal<"A", string> | ConcatArray<Nominal<"A", string>>)[]): Nominal<"A", string>[]; }
+>concat : { <U>(...items: (ConcatArray<Nominal<"A", string>> | ConcatArray<U>)[]): (Nominal<"A", string> | U)[]; (...items: (Nominal<"A", string> | ConcatArray<Nominal<"A", string>>)[]): Nominal<"A", string>[]; }
 >Array.from(b) : Nominal<"A", string>[]
 >Array.from : { <T>(arrayLike: ArrayLike<T>): T[]; <T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; <T>(iterable: Iterable<T> | ArrayLike<T>): T[]; <T, U>(iterable: Iterable<T> | ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): U[]; }
 >Array : ArrayConstructor

tests/baselines/reference/iteratorSpreadInArray6.types

@@ -38,10 +38,10 @@ var array: number[] = [0, 1];
 >1 : 1
 
 array.concat([...new SymbolIterator]);
->array.concat([...new SymbolIterator]) : any
->array.concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>array.concat([...new SymbolIterator]) : (number | symbol)[]
+>array.concat : { <U>(...items: (ConcatArray<number> | ConcatArray<U>)[]): (number | U)[]; (...items: (number | ConcatArray<number>)[]): number[]; }
 >array : number[]
->concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>concat : { <U>(...items: (ConcatArray<number> | ConcatArray<U>)[]): (number | U)[]; (...items: (number | ConcatArray<number>)[]): number[]; }
 >[...new SymbolIterator] : symbol[]
 >...new SymbolIterator : symbol
 >new SymbolIterator : SymbolIterator

tests/baselines/reference/iteratorSpreadInArray7.types

@@ -36,9 +36,9 @@ var array: symbol[];
 
 array.concat([...new SymbolIterator]);
 >array.concat([...new SymbolIterator]) : symbol[]
->array.concat : { (...items: ConcatArray<symbol>[]): symbol[]; (...items: (symbol | ConcatArray<symbol>)[]): symbol[]; }
+>array.concat : { <U>(...items: (ConcatArray<symbol> | ConcatArray<U>)[]): (symbol | U)[]; (...items: (symbol | ConcatArray<symbol>)[]): symbol[]; }
 >array : symbol[]
->concat : { (...items: ConcatArray<symbol>[]): symbol[]; (...items: (symbol | ConcatArray<symbol>)[]): symbol[]; }
+>concat : { <U>(...items: (ConcatArray<symbol> | ConcatArray<U>)[]): (symbol | U)[]; (...items: (symbol | ConcatArray<symbol>)[]): symbol[]; }
 >[...new SymbolIterator] : symbol[]
 >...new SymbolIterator : symbol
 >new SymbolIterator : SymbolIterator

tests/baselines/reference/mappedTypesArraysTuples.types

@@ -196,9 +196,9 @@ function f2<T extends any[]>(a: Boxified<T>) {
     let y: Box<any>[] = a.concat(a);
 >y : Box<any>[]
 >a.concat(a) : Box<any>[]
->a.concat : { (...items: ConcatArray<Box<any>>[]): Box<any>[]; (...items: (Box<any> | ConcatArray<Box<any>>)[]): Box<any>[]; }
+>a.concat : { <U>(...items: (ConcatArray<Box<any>> | ConcatArray<U>)[]): (Box<any> | U)[]; (...items: (Box<any> | ConcatArray<Box<any>>)[]): Box<any>[]; }
 >a : Boxified<T>
->concat : { (...items: ConcatArray<Box<any>>[]): Box<any>[]; (...items: (Box<any> | ConcatArray<Box<any>>)[]): Box<any>[]; }
+>concat : { <U>(...items: (ConcatArray<Box<any>> | ConcatArray<U>)[]): (Box<any> | U)[]; (...items: (Box<any> | ConcatArray<Box<any>>)[]): Box<any>[]; }
 >a : Boxified<T>
 }
 

tests/baselines/reference/parserRealSource4.types

@@ -418,14 +418,14 @@ module TypeScript {
 
             return this.primaryTable.getAllKeys().concat(this.secondaryTable.getAllKeys());
 >this.primaryTable.getAllKeys().concat(this.secondaryTable.getAllKeys()) : string[]
->this.primaryTable.getAllKeys().concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>this.primaryTable.getAllKeys().concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >this.primaryTable.getAllKeys() : string[]
 >this.primaryTable.getAllKeys : () => string[]
 >this.primaryTable : IHashTable
 >this : this
 >primaryTable : IHashTable
 >getAllKeys : () => string[]
->concat : { (...items: ConcatArray<string>[]): string[]; (...items: (string | ConcatArray<string>)[]): string[]; }
+>concat : { <U>(...items: (ConcatArray<string> | ConcatArray<U>)[]): (string | U)[]; (...items: (string | ConcatArray<string>)[]): string[]; }
 >this.secondaryTable.getAllKeys() : string[]
 >this.secondaryTable.getAllKeys : () => string[]
 >this.secondaryTable : IHashTable

tests/baselines/reference/parserharness.types

@@ -4775,9 +4775,9 @@ module Harness {
 >lines = lines.concat(v.file.lines) : any[]
 >lines : any[]
 >lines.concat(v.file.lines) : any[]
->lines.concat : { (...items: ConcatArray<any>[]): any[]; (...items: any[]): any[]; }
+>lines.concat : { <U>(...items: (ConcatArray<any> | ConcatArray<U>)[]): any[]; (...items: any[]): any[]; }
 >lines : any[]
->concat : { (...items: ConcatArray<any>[]): any[]; (...items: any[]): any[]; }
+>concat : { <U>(...items: (ConcatArray<any> | ConcatArray<U>)[]): any[]; (...items: any[]): any[]; }
 >v.file.lines : string[]
 >v.file : WriterAggregator
 >v : { filename: string; file: WriterAggregator; }