Merge pull request microsoft#22197 from Microsoft/fixConditionalTypes

ahejlsberg · web-flow · commit bb05122a50fa · 2018-03-01T10:27:15.000-08:00
Conditional type fixes
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -3821,16 +3821,27 @@ namespace ts {
         type: InstantiableType | UnionOrIntersectionType;
     }
 
-    // T extends U ? X : Y (TypeFlags.Conditional)
-    export interface ConditionalType extends InstantiableType {
+    export interface ConditionalRoot {
+        node: ConditionalTypeNode;
         checkType: Type;
         extendsType: Type;
         trueType: Type;
         falseType: Type;
-        /* @internal */
+        isDistributive: boolean;
         inferTypeParameters: TypeParameter[];
-        /* @internal */
-        target?: ConditionalType;
+        outerTypeParameters?: TypeParameter[];
+        instantiations?: Map<Type>;
+        aliasSymbol: Symbol;
+        aliasTypeArguments: Type[];
+    }
+
+    // T extends U ? X : Y (TypeFlags.Conditional)
+    export interface ConditionalType extends InstantiableType {
+        root: ConditionalRoot;
+        checkType: Type;
+        extendsType: Type;
+        resolvedTrueType?: Type;
+        resolvedFalseType?: Type;
         /* @internal */
         mapper?: TypeMapper;
     }
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2192,11 +2192,25 @@ declare namespace ts {
     interface IndexType extends InstantiableType {
         type: InstantiableType | UnionOrIntersectionType;
     }
-    interface ConditionalType extends InstantiableType {
+    interface ConditionalRoot {
+        node: ConditionalTypeNode;
         checkType: Type;
         extendsType: Type;
         trueType: Type;
         falseType: Type;
+        isDistributive: boolean;
+        inferTypeParameters: TypeParameter[];
+        outerTypeParameters?: TypeParameter[];
+        instantiations?: Map<Type>;
+        aliasSymbol: Symbol;
+        aliasTypeArguments: Type[];
+    }
+    interface ConditionalType extends InstantiableType {
+        root: ConditionalRoot;
+        checkType: Type;
+        extendsType: Type;
+        resolvedTrueType?: Type;
+        resolvedFalseType?: Type;
     }
     interface SubstitutionType extends InstantiableType {
         typeParameter: TypeParameter;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
@@ -2192,11 +2192,25 @@ declare namespace ts {
     interface IndexType extends InstantiableType {
         type: InstantiableType | UnionOrIntersectionType;
     }
-    interface ConditionalType extends InstantiableType {
+    interface ConditionalRoot {
+        node: ConditionalTypeNode;
         checkType: Type;
         extendsType: Type;
         trueType: Type;
         falseType: Type;
+        isDistributive: boolean;
+        inferTypeParameters: TypeParameter[];
+        outerTypeParameters?: TypeParameter[];
+        instantiations?: Map<Type>;
+        aliasSymbol: Symbol;
+        aliasTypeArguments: Type[];
+    }
+    interface ConditionalType extends InstantiableType {
+        root: ConditionalRoot;
+        checkType: Type;
+        extendsType: Type;
+        resolvedTrueType?: Type;
+        resolvedFalseType?: Type;
     }
     interface SubstitutionType extends InstantiableType {
         typeParameter: TypeParameter;
diff --git a/tests/baselines/reference/conditionalTypes1.errors.txt b/tests/baselines/reference/conditionalTypes1.errors.txt
@@ -157,7 +157,7 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(275,43): error TS
     
     type T20 = TypeName<string | (() => void)>;  // "string" | "function"
     type T21 = TypeName<any>;  // "string" | "number" | "boolean" | "undefined" | "function" | "object"
-    type T22 = TypeName<never>;  // "string" | "number" | "boolean" | "undefined" | "function" | "object"
+    type T22 = TypeName<never>;  // never
     type T23 = TypeName<{}>;  // "object"
     
     type KnockoutObservable<T> = { object: T };
@@ -329,7 +329,7 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(275,43): error TS
     type Q1 = IsString<number>;  // false
     type Q2 = IsString<"abc">;  // true
     type Q3 = IsString<any>;  // boolean
-    type Q4 = IsString<never>;  // boolean
+    type Q4 = IsString<never>;  // never
     
     type N1 = Not<false>;  // true
     type N2 = Not<true>;  // false
@@ -357,9 +357,9 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(275,43): error TS
     
     type T40 = never extends never ? true : false;  // true
     type T41 = number extends never ? true : false;  // false
-    type T42 = never extends number ? true : false;  // boolean
+    type T42 = never extends number ? true : false;  // true
     
-    type IsNever<T> = T extends never ? true : false;
+    type IsNever<T> = [T] extends [never] ? true : false;
     
     type T50 = IsNever<never>;  // true
     type T51 = IsNever<number>;  // false
diff --git a/tests/baselines/reference/conditionalTypes1.js b/tests/baselines/reference/conditionalTypes1.js
@@ -64,7 +64,7 @@ type TypeName<T> =
 
 type T20 = TypeName<string | (() => void)>;  // "string" | "function"
 type T21 = TypeName<any>;  // "string" | "number" | "boolean" | "undefined" | "function" | "object"
-type T22 = TypeName<never>;  // "string" | "number" | "boolean" | "undefined" | "function" | "object"
+type T22 = TypeName<never>;  // never
 type T23 = TypeName<{}>;  // "object"
 
 type KnockoutObservable<T> = { object: T };
@@ -172,7 +172,7 @@ type IsString<T> = Extends<T, string>;
 type Q1 = IsString<number>;  // false
 type Q2 = IsString<"abc">;  // true
 type Q3 = IsString<any>;  // boolean
-type Q4 = IsString<never>;  // boolean
+type Q4 = IsString<never>;  // never
 
 type N1 = Not<false>;  // true
 type N2 = Not<true>;  // false
@@ -200,9 +200,9 @@ type O9 = Or<boolean, boolean>;  // boolean
 
 type T40 = never extends never ? true : false;  // true
 type T41 = number extends never ? true : false;  // false
-type T42 = never extends number ? true : false;  // boolean
+type T42 = never extends number ? true : false;  // true
 
-type IsNever<T> = T extends never ? true : false;
+type IsNever<T> = [T] extends [never] ? true : false;
 
 type T50 = IsNever<never>;  // true
 type T51 = IsNever<number>;  // false
@@ -551,7 +551,7 @@ declare type O9 = Or<boolean, boolean>;
 declare type T40 = never extends never ? true : false;
 declare type T41 = number extends never ? true : false;
 declare type T42 = never extends number ? true : false;
-declare type IsNever<T> = T extends never ? true : false;
+declare type IsNever<T> = [T] extends [never] ? true : false;
 declare type T50 = IsNever<never>;
 declare type T51 = IsNever<number>;
 declare type T52 = IsNever<any>;
@@ -572,7 +572,7 @@ declare type T82 = Eq2<false, true>;
 declare type T83 = Eq2<false, false>;
 declare type Foo<T> = T extends string ? boolean : number;
 declare type Bar<T> = T extends string ? boolean : number;
-declare const convert: <U>(value: Foo<U>) => Foo<U>;
+declare const convert: <U>(value: Foo<U>) => Bar<U>;
 declare type Baz<T> = Foo<T>;
 declare const convert2: <T>(value: Foo<T>) => Foo<T>;
 declare function f31<T>(): void;
diff --git a/tests/baselines/reference/conditionalTypes1.symbols b/tests/baselines/reference/conditionalTypes1.symbols
@@ -243,7 +243,7 @@ type T21 = TypeName<any>;  // "string" | "number" | "boolean" | "undefined" | "f
 >T21 : Symbol(T21, Decl(conditionalTypes1.ts, 63, 43))
 >TypeName : Symbol(TypeName, Decl(conditionalTypes1.ts, 53, 43))
 
-type T22 = TypeName<never>;  // "string" | "number" | "boolean" | "undefined" | "function" | "object"
+type T22 = TypeName<never>;  // never
 >T22 : Symbol(T22, Decl(conditionalTypes1.ts, 64, 25))
 >TypeName : Symbol(TypeName, Decl(conditionalTypes1.ts, 53, 43))
 
@@ -668,7 +668,7 @@ type Q3 = IsString<any>;  // boolean
 >Q3 : Symbol(Q3, Decl(conditionalTypes1.ts, 171, 26))
 >IsString : Symbol(IsString, Decl(conditionalTypes1.ts, 166, 63))
 
-type Q4 = IsString<never>;  // boolean
+type Q4 = IsString<never>;  // never
 >Q4 : Symbol(Q4, Decl(conditionalTypes1.ts, 172, 24))
 >IsString : Symbol(IsString, Decl(conditionalTypes1.ts, 166, 63))
 
@@ -762,16 +762,16 @@ type T40 = never extends never ? true : false;  // true
 type T41 = number extends never ? true : false;  // false
 >T41 : Symbol(T41, Decl(conditionalTypes1.ts, 199, 46))
 
-type T42 = never extends number ? true : false;  // boolean
+type T42 = never extends number ? true : false;  // true
 >T42 : Symbol(T42, Decl(conditionalTypes1.ts, 200, 47))
 
-type IsNever<T> = T extends never ? true : false;
+type IsNever<T> = [T] extends [never] ? true : false;
 >IsNever : Symbol(IsNever, Decl(conditionalTypes1.ts, 201, 47))
 >T : Symbol(T, Decl(conditionalTypes1.ts, 203, 13))
 >T : Symbol(T, Decl(conditionalTypes1.ts, 203, 13))
 
 type T50 = IsNever<never>;  // true
->T50 : Symbol(T50, Decl(conditionalTypes1.ts, 203, 49))
+>T50 : Symbol(T50, Decl(conditionalTypes1.ts, 203, 53))
 >IsNever : Symbol(IsNever, Decl(conditionalTypes1.ts, 201, 47))
 
 type T51 = IsNever<number>;  // false
diff --git a/tests/baselines/reference/conditionalTypes1.types b/tests/baselines/reference/conditionalTypes1.types
@@ -254,8 +254,8 @@ type T21 = TypeName<any>;  // "string" | "number" | "boolean" | "undefined" | "f
 >T21 : "string" | "number" | "boolean" | "undefined" | "object" | "function"
 >TypeName : TypeName<T>
 
-type T22 = TypeName<never>;  // "string" | "number" | "boolean" | "undefined" | "function" | "object"
->T22 : "string" | "number" | "boolean" | "undefined" | "object" | "function"
+type T22 = TypeName<never>;  // never
+>T22 : never
 >TypeName : TypeName<T>
 
 type T23 = TypeName<{}>;  // "object"
@@ -741,8 +741,8 @@ type Q3 = IsString<any>;  // boolean
 >Q3 : boolean
 >IsString : Extends<T, string>
 
-type Q4 = IsString<never>;  // boolean
->Q4 : boolean
+type Q4 = IsString<never>;  // never
+>Q4 : never
 >IsString : Extends<T, string>
 
 type N1 = Not<false>;  // true
@@ -865,12 +865,12 @@ type T41 = number extends never ? true : false;  // false
 >true : true
 >false : false
 
-type T42 = never extends number ? true : false;  // boolean
->T42 : boolean
+type T42 = never extends number ? true : false;  // true
+>T42 : true
 >true : true
 >false : false
 
-type IsNever<T> = T extends never ? true : false;
+type IsNever<T> = [T] extends [never] ? true : false;
 >IsNever : IsNever<T>
 >T : T
 >T : T
@@ -1010,8 +1010,8 @@ type Bar<T> = T extends string ? boolean : number;
 >T : T
 
 const convert = <U>(value: Foo<U>): Bar<U> => value;
->convert : <U>(value: Foo<U>) => Foo<U>
-><U>(value: Foo<U>): Bar<U> => value : <U>(value: Foo<U>) => Foo<U>
+>convert : <U>(value: Foo<U>) => Bar<U>
+><U>(value: Foo<U>): Bar<U> => value : <U>(value: Foo<U>) => Bar<U>
 >U : U
 >value : Foo<U>
 >Foo : Foo<T>
@@ -1095,7 +1095,7 @@ function f33<T, U>() {
 >U : U
 
     type T2 = Bar<T & U>;
->T2 : Foo<T & U>
+>T2 : Bar<T & U>
 >Bar : Bar<T>
 >T : T
 >U : U
@@ -1106,7 +1106,7 @@ function f33<T, U>() {
 
     var z: T2;
 >z : Foo<T & U>
->T2 : Foo<T & U>
+>T2 : Bar<T & U>
 }
 
 // Repro from #21823
@@ -1236,7 +1236,7 @@ function f50() {
 >T : T
 
     type Omit<T extends object> = { [P in keyof T]: If<Eq<T[P], never>, never, P>; }[keyof T];
->Omit : { [P in keyof T]: (T[P] extends never ? boolean : false) extends false ? P : never; }[keyof T]
+>Omit : { [P in keyof T]: (T[P] extends never ? never : false) extends false ? P : never; }[keyof T]
 >T : T
 >P : P
 >T : T
@@ -1263,7 +1263,7 @@ function f50() {
 
     type A = Omit<{ a: void; b: never; }>;  // 'a'
 >A : "a"
->Omit : { [P in keyof T]: (T[P] extends never ? boolean : false) extends false ? P : never; }[keyof T]
+>Omit : { [P in keyof T]: (T[P] extends never ? never : false) extends false ? P : never; }[keyof T]
 >a : void
 >b : never
 
diff --git a/tests/baselines/reference/inferTypes1.errors.txt b/tests/baselines/reference/inferTypes1.errors.txt
@@ -50,7 +50,7 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322:
     type T13 = ReturnType<(<T extends U, U extends number[]>() => T)>;  // number[]
     type T14 = ReturnType<typeof f1>;  // { a: number, b: string }
     type T15 = ReturnType<any>;  // any
-    type T16 = ReturnType<never>;  // any
+    type T16 = ReturnType<never>;  // never
     type T17 = ReturnType<string>;  // Error
                           ~~~~~~
 !!! error TS2344: Type 'string' does not satisfy the constraint '(...args: any[]) => any'.
@@ -61,7 +61,7 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322:
     
     type U10 = InstanceType<typeof C>;  // C
     type U11 = InstanceType<any>;  // any
-    type U12 = InstanceType<never>;  // any
+    type U12 = InstanceType<never>;  // never
     type U13 = InstanceType<string>;  // Error
                             ~~~~~~
 !!! error TS2344: Type 'string' does not satisfy the constraint 'new (...args: any[]) => any'.
@@ -72,7 +72,7 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322:
     
     type ArgumentType<T extends (x: any) => any> = T extends (a: infer A) => any ? A : any;
     
-    type T20 = ArgumentType<() => void>;  // never
+    type T20 = ArgumentType<() => void>;  // {}
     type T21 = ArgumentType<(x: string) => number>;  // string
     type T22 = ArgumentType<(x?: string) => number>;  // string | undefined
     type T23 = ArgumentType<(...args: string[]) => number>;  // string
@@ -84,7 +84,7 @@ tests/cases/conformance/types/conditional/inferTypes1.ts(134,40): error TS2322:
 !!! error TS2344: Type 'Function' does not satisfy the constraint '(x: any) => any'.
 !!! error TS2344:   Type 'Function' provides no match for the signature '(x: any): any'.
     type T26 = ArgumentType<any>;  // any
-    type T27 = ArgumentType<never>;  // any
+    type T27 = ArgumentType<never>;  // never
     
     type X1<T extends { x: any, y: any }> = T extends { x: infer X, y: infer Y } ? [X, Y] : any;
     
diff --git a/tests/baselines/reference/inferTypes1.js b/tests/baselines/reference/inferTypes1.js
@@ -28,26 +28,26 @@ type T12 = ReturnType<(<T>() => T)>;  // {}
 type T13 = ReturnType<(<T extends U, U extends number[]>() => T)>;  // number[]
 type T14 = ReturnType<typeof f1>;  // { a: number, b: string }
 type T15 = ReturnType<any>;  // any
-type T16 = ReturnType<never>;  // any
+type T16 = ReturnType<never>;  // never
 type T17 = ReturnType<string>;  // Error
 type T18 = ReturnType<Function>;  // Error
 
 type U10 = InstanceType<typeof C>;  // C
 type U11 = InstanceType<any>;  // any
-type U12 = InstanceType<never>;  // any
+type U12 = InstanceType<never>;  // never
 type U13 = InstanceType<string>;  // Error
 type U14 = InstanceType<Function>;  // Error
 
 type ArgumentType<T extends (x: any) => any> = T extends (a: infer A) => any ? A : any;
 
-type T20 = ArgumentType<() => void>;  // never
+type T20 = ArgumentType<() => void>;  // {}
 type T21 = ArgumentType<(x: string) => number>;  // string
 type T22 = ArgumentType<(x?: string) => number>;  // string | undefined
 type T23 = ArgumentType<(...args: string[]) => number>;  // string
 type T24 = ArgumentType<(x: string, y: string) => number>;  // Error
 type T25 = ArgumentType<Function>;  // Error
 type T26 = ArgumentType<any>;  // any
-type T27 = ArgumentType<never>;  // any
+type T27 = ArgumentType<never>;  // never
 
 type X1<T extends { x: any, y: any }> = T extends { x: infer X, y: infer Y } ? [X, Y] : any;
 
diff --git a/tests/baselines/reference/inferTypes1.symbols b/tests/baselines/reference/inferTypes1.symbols
@@ -106,7 +106,7 @@ type T15 = ReturnType<any>;  // any
 >T15 : Symbol(T15, Decl(inferTypes1.ts, 27, 33))
 >ReturnType : Symbol(ReturnType, Decl(lib.d.ts, --, --))
 
-type T16 = ReturnType<never>;  // any
+type T16 = ReturnType<never>;  // never
 >T16 : Symbol(T16, Decl(inferTypes1.ts, 28, 27))
 >ReturnType : Symbol(ReturnType, Decl(lib.d.ts, --, --))
 
@@ -128,7 +128,7 @@ type U11 = InstanceType<any>;  // any
 >U11 : Symbol(U11, Decl(inferTypes1.ts, 33, 34))
 >InstanceType : Symbol(InstanceType, Decl(lib.d.ts, --, --))
 
-type U12 = InstanceType<never>;  // any
+type U12 = InstanceType<never>;  // never
 >U12 : Symbol(U12, Decl(inferTypes1.ts, 34, 29))
 >InstanceType : Symbol(InstanceType, Decl(lib.d.ts, --, --))
 
@@ -150,7 +150,7 @@ type ArgumentType<T extends (x: any) => any> = T extends (a: infer A) => any ? A
 >A : Symbol(A, Decl(inferTypes1.ts, 39, 66))
 >A : Symbol(A, Decl(inferTypes1.ts, 39, 66))
 
-type T20 = ArgumentType<() => void>;  // never
+type T20 = ArgumentType<() => void>;  // {}
 >T20 : Symbol(T20, Decl(inferTypes1.ts, 39, 87))
 >ArgumentType : Symbol(ArgumentType, Decl(inferTypes1.ts, 37, 34))
 
@@ -184,7 +184,7 @@ type T26 = ArgumentType<any>;  // any
 >T26 : Symbol(T26, Decl(inferTypes1.ts, 46, 34))
 >ArgumentType : Symbol(ArgumentType, Decl(inferTypes1.ts, 37, 34))
 
-type T27 = ArgumentType<never>;  // any
+type T27 = ArgumentType<never>;  // never
 >T27 : Symbol(T27, Decl(inferTypes1.ts, 47, 29))
 >ArgumentType : Symbol(ArgumentType, Decl(inferTypes1.ts, 37, 34))
 
diff --git a/tests/baselines/reference/inferTypes1.types b/tests/baselines/reference/inferTypes1.types
diff --git a/tests/baselines/reference/mappedTypeRecursiveInference.types b/tests/baselines/reference/mappedTypeRecursiveInference.types
diff --git a/tests/cases/conformance/types/conditional/conditionalTypes1.ts b/tests/cases/conformance/types/conditional/conditionalTypes1.ts
diff --git a/tests/cases/conformance/types/conditional/inferTypes1.ts b/tests/cases/conformance/types/conditional/inferTypes1.ts
