Add inference priority level for conditional types in contravariant positions (#35199)

ahejlsberg · web-flow · commit 94d4023043dd · 2019-11-21T13:05:44.000-08:00
* Add inference priority level for conditional types in contravariant positions

* Accept new API baselines

* Add regression tests

* Accept new baselines
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -17552,9 +17552,12 @@ namespace ts {
                     inferFromTypes(getTrueTypeFromConditionalType(<ConditionalType>source), getTrueTypeFromConditionalType(<ConditionalType>target));
                     inferFromTypes(getFalseTypeFromConditionalType(<ConditionalType>source), getFalseTypeFromConditionalType(<ConditionalType>target));
                 }
-                else if (target.flags & TypeFlags.Conditional && !contravariant) {
+                else if (target.flags & TypeFlags.Conditional) {
+                    const savePriority = priority;
+                    priority |= contravariant ? InferencePriority.ContravariantConditional : 0;
                     const targetTypes = [getTrueTypeFromConditionalType(<ConditionalType>target), getFalseTypeFromConditionalType(<ConditionalType>target)];
                     inferToMultipleTypes(source, targetTypes, target.flags);
+                    priority = savePriority;
                 }
                 else if (target.flags & TypeFlags.UnionOrIntersection) {
                     inferToMultipleTypes(source, (<UnionOrIntersectionType>target).types, target.flags);
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -4740,11 +4740,12 @@ namespace ts {
         HomomorphicMappedType        = 1 << 1,  // Reverse inference for homomorphic mapped type
         PartialHomomorphicMappedType = 1 << 2,  // Partial reverse inference for homomorphic mapped type
         MappedTypeConstraint         = 1 << 3,  // Reverse inference for mapped type
-        ReturnType                   = 1 << 4,  // Inference made from return type of generic function
-        LiteralKeyof                 = 1 << 5,  // Inference made from a string literal to a keyof T
-        NoConstraints                = 1 << 6,  // Don't infer from constraints of instantiable types
-        AlwaysStrict                 = 1 << 7,  // Always use strict rules for contravariant inferences
-        MaxValue                     = 1 << 8,  // Seed for inference priority tracking
+        ContravariantConditional     = 1 << 4,  // Conditional type in contravariant position
+        ReturnType                   = 1 << 5,  // Inference made from return type of generic function
+        LiteralKeyof                 = 1 << 6,  // Inference made from a string literal to a keyof T
+        NoConstraints                = 1 << 7,  // Don't infer from constraints of instantiable types
+        AlwaysStrict                 = 1 << 8,  // Always use strict rules for contravariant inferences
+        MaxValue                     = 1 << 9,  // Seed for inference priority tracking
 
         PriorityImpliesCombination = ReturnType | MappedTypeConstraint | LiteralKeyof,  // These priorities imply that the resulting type should be a combination of all candidates
         Circularity = -1,  // Inference circularity (value less than all other priorities)
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2500,12 +2500,13 @@ declare namespace ts {
         HomomorphicMappedType = 2,
         PartialHomomorphicMappedType = 4,
         MappedTypeConstraint = 8,
-        ReturnType = 16,
-        LiteralKeyof = 32,
-        NoConstraints = 64,
-        AlwaysStrict = 128,
-        MaxValue = 256,
-        PriorityImpliesCombination = 56,
+        ContravariantConditional = 16,
+        ReturnType = 32,
+        LiteralKeyof = 64,
+        NoConstraints = 128,
+        AlwaysStrict = 256,
+        MaxValue = 512,
+        PriorityImpliesCombination = 104,
         Circularity = -1
     }
     /** @deprecated Use FileExtensionInfo instead. */
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
@@ -2500,12 +2500,13 @@ declare namespace ts {
         HomomorphicMappedType = 2,
         PartialHomomorphicMappedType = 4,
         MappedTypeConstraint = 8,
-        ReturnType = 16,
-        LiteralKeyof = 32,
-        NoConstraints = 64,
-        AlwaysStrict = 128,
-        MaxValue = 256,
-        PriorityImpliesCombination = 56,
+        ContravariantConditional = 16,
+        ReturnType = 32,
+        LiteralKeyof = 64,
+        NoConstraints = 128,
+        AlwaysStrict = 256,
+        MaxValue = 512,
+        PriorityImpliesCombination = 104,
         Circularity = -1
     }
     /** @deprecated Use FileExtensionInfo instead. */
diff --git a/tests/baselines/reference/conditionalTypes2.errors.txt b/tests/baselines/reference/conditionalTypes2.errors.txt
@@ -273,4 +273,47 @@ tests/cases/conformance/types/conditional/conditionalTypes2.ts(75,12): error TS2
     type Hmm<T, U extends T> = U extends T ? { [K in keyof U]: number } : never;
     type What = Hmm<{}, { a: string }>
     const w: What = { a: 4 };
+    
+    // Repro from #33568
+    
+    declare function save(_response: IRootResponse<string>): void;
+    
+    exportCommand(save);
+    
+    declare function exportCommand<TResponse>(functionToCall: IExportCallback<TResponse>): void;
+    
+    interface IExportCallback<TResponse> {
+    	(response: IRootResponse<TResponse>): void;
+    }
+    
+    type IRootResponse<TResponse> =
+    	TResponse extends IRecord ? IRecordResponse<TResponse> : IResponse<TResponse>;
+    
+    interface IRecord {
+    	readonly Id: string;
+    }
+    
+    declare type IRecordResponse<T extends IRecord> = IResponse<T> & {
+    	sendRecord(): void;
+    };
+    
+    declare type IResponse<T> = {
+    	sendValue(name: keyof GetAllPropertiesOfType<T, string>): void;
+    };
+    
+    declare type GetPropertyNamesOfType<T, RestrictToType> = {
+    	[PropertyName in Extract<keyof T, string>]: T[PropertyName] extends RestrictToType ? PropertyName : never
+    }[Extract<keyof T, string>];
+    
+    declare type GetAllPropertiesOfType<T, RestrictToType> = Pick<
+    	T,
+    	GetPropertyNamesOfType<Required<T>, RestrictToType>
+    >;
+    
+    // Repro from #33568
+    
+    declare function ff(x: Foo3<string>): void;
+    declare function gg<T>(f: (x: Foo3<T>) => void): void;
+    type Foo3<T> = T extends number ? { n: T } : { x: T };
+    gg(ff);
     
diff --git a/tests/baselines/reference/conditionalTypes2.js b/tests/baselines/reference/conditionalTypes2.js
@@ -194,6 +194,49 @@ type PCCB = ProductComplementComplement['b'];
 type Hmm<T, U extends T> = U extends T ? { [K in keyof U]: number } : never;
 type What = Hmm<{}, { a: string }>
 const w: What = { a: 4 };
+
+// Repro from #33568
+
+declare function save(_response: IRootResponse<string>): void;
+
+exportCommand(save);
+
+declare function exportCommand<TResponse>(functionToCall: IExportCallback<TResponse>): void;
+
+interface IExportCallback<TResponse> {
+	(response: IRootResponse<TResponse>): void;
+}
+
+type IRootResponse<TResponse> =
+	TResponse extends IRecord ? IRecordResponse<TResponse> : IResponse<TResponse>;
+
+interface IRecord {
+	readonly Id: string;
+}
+
+declare type IRecordResponse<T extends IRecord> = IResponse<T> & {
+	sendRecord(): void;
+};
+
+declare type IResponse<T> = {
+	sendValue(name: keyof GetAllPropertiesOfType<T, string>): void;
+};
+
+declare type GetPropertyNamesOfType<T, RestrictToType> = {
+	[PropertyName in Extract<keyof T, string>]: T[PropertyName] extends RestrictToType ? PropertyName : never
+}[Extract<keyof T, string>];
+
+declare type GetAllPropertiesOfType<T, RestrictToType> = Pick<
+	T,
+	GetPropertyNamesOfType<Required<T>, RestrictToType>
+>;
+
+// Repro from #33568
+
+declare function ff(x: Foo3<string>): void;
+declare function gg<T>(f: (x: Foo3<T>) => void): void;
+type Foo3<T> = T extends number ? { n: T } : { x: T };
+gg(ff);
 
 
 //// [conditionalTypes2.js]
@@ -272,6 +315,8 @@ function foo(value) {
     }
 }
 var w = { a: 4 };
+exportCommand(save);
+gg(ff);
 
 
 //// [conditionalTypes2.d.ts]
@@ -406,3 +451,29 @@ declare type What = Hmm<{}, {
     a: string;
 }>;
 declare const w: What;
+declare function save(_response: IRootResponse<string>): void;
+declare function exportCommand<TResponse>(functionToCall: IExportCallback<TResponse>): void;
+interface IExportCallback<TResponse> {
+    (response: IRootResponse<TResponse>): void;
+}
+declare type IRootResponse<TResponse> = TResponse extends IRecord ? IRecordResponse<TResponse> : IResponse<TResponse>;
+interface IRecord {
+    readonly Id: string;
+}
+declare type IRecordResponse<T extends IRecord> = IResponse<T> & {
+    sendRecord(): void;
+};
+declare type IResponse<T> = {
+    sendValue(name: keyof GetAllPropertiesOfType<T, string>): void;
+};
+declare type GetPropertyNamesOfType<T, RestrictToType> = {
+    [PropertyName in Extract<keyof T, string>]: T[PropertyName] extends RestrictToType ? PropertyName : never;
+}[Extract<keyof T, string>];
+declare type GetAllPropertiesOfType<T, RestrictToType> = Pick<T, GetPropertyNamesOfType<Required<T>, RestrictToType>>;
+declare function ff(x: Foo3<string>): void;
+declare function gg<T>(f: (x: Foo3<T>) => void): void;
+declare type Foo3<T> = T extends number ? {
+    n: T;
+} : {
+    x: T;
+};
diff --git a/tests/baselines/reference/conditionalTypes2.symbols b/tests/baselines/reference/conditionalTypes2.symbols
@@ -707,3 +707,137 @@ const w: What = { a: 4 };
 >What : Symbol(What, Decl(conditionalTypes2.ts, 192, 76))
 >a : Symbol(a, Decl(conditionalTypes2.ts, 194, 17))
 
+// Repro from #33568
+
+declare function save(_response: IRootResponse<string>): void;
+>save : Symbol(save, Decl(conditionalTypes2.ts, 194, 25))
+>_response : Symbol(_response, Decl(conditionalTypes2.ts, 198, 22))
+>IRootResponse : Symbol(IRootResponse, Decl(conditionalTypes2.ts, 206, 1))
+
+exportCommand(save);
+>exportCommand : Symbol(exportCommand, Decl(conditionalTypes2.ts, 200, 20))
+>save : Symbol(save, Decl(conditionalTypes2.ts, 194, 25))
+
+declare function exportCommand<TResponse>(functionToCall: IExportCallback<TResponse>): void;
+>exportCommand : Symbol(exportCommand, Decl(conditionalTypes2.ts, 200, 20))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 202, 31))
+>functionToCall : Symbol(functionToCall, Decl(conditionalTypes2.ts, 202, 42))
+>IExportCallback : Symbol(IExportCallback, Decl(conditionalTypes2.ts, 202, 92))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 202, 31))
+
+interface IExportCallback<TResponse> {
+>IExportCallback : Symbol(IExportCallback, Decl(conditionalTypes2.ts, 202, 92))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 204, 26))
+
+	(response: IRootResponse<TResponse>): void;
+>response : Symbol(response, Decl(conditionalTypes2.ts, 205, 2))
+>IRootResponse : Symbol(IRootResponse, Decl(conditionalTypes2.ts, 206, 1))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 204, 26))
+}
+
+type IRootResponse<TResponse> =
+>IRootResponse : Symbol(IRootResponse, Decl(conditionalTypes2.ts, 206, 1))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 208, 19))
+
+	TResponse extends IRecord ? IRecordResponse<TResponse> : IResponse<TResponse>;
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 208, 19))
+>IRecord : Symbol(IRecord, Decl(conditionalTypes2.ts, 209, 79))
+>IRecordResponse : Symbol(IRecordResponse, Decl(conditionalTypes2.ts, 213, 1))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 208, 19))
+>IResponse : Symbol(IResponse, Decl(conditionalTypes2.ts, 217, 2))
+>TResponse : Symbol(TResponse, Decl(conditionalTypes2.ts, 208, 19))
+
+interface IRecord {
+>IRecord : Symbol(IRecord, Decl(conditionalTypes2.ts, 209, 79))
+
+	readonly Id: string;
+>Id : Symbol(IRecord.Id, Decl(conditionalTypes2.ts, 211, 19))
+}
+
+declare type IRecordResponse<T extends IRecord> = IResponse<T> & {
+>IRecordResponse : Symbol(IRecordResponse, Decl(conditionalTypes2.ts, 213, 1))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 215, 29))
+>IRecord : Symbol(IRecord, Decl(conditionalTypes2.ts, 209, 79))
+>IResponse : Symbol(IResponse, Decl(conditionalTypes2.ts, 217, 2))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 215, 29))
+
+	sendRecord(): void;
+>sendRecord : Symbol(sendRecord, Decl(conditionalTypes2.ts, 215, 66))
+
+};
+
+declare type IResponse<T> = {
+>IResponse : Symbol(IResponse, Decl(conditionalTypes2.ts, 217, 2))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 219, 23))
+
+	sendValue(name: keyof GetAllPropertiesOfType<T, string>): void;
+>sendValue : Symbol(sendValue, Decl(conditionalTypes2.ts, 219, 29))
+>name : Symbol(name, Decl(conditionalTypes2.ts, 220, 11))
+>GetAllPropertiesOfType : Symbol(GetAllPropertiesOfType, Decl(conditionalTypes2.ts, 225, 28))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 219, 23))
+
+};
+
+declare type GetPropertyNamesOfType<T, RestrictToType> = {
+>GetPropertyNamesOfType : Symbol(GetPropertyNamesOfType, Decl(conditionalTypes2.ts, 221, 2))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 223, 36))
+>RestrictToType : Symbol(RestrictToType, Decl(conditionalTypes2.ts, 223, 38))
+
+	[PropertyName in Extract<keyof T, string>]: T[PropertyName] extends RestrictToType ? PropertyName : never
+>PropertyName : Symbol(PropertyName, Decl(conditionalTypes2.ts, 224, 2))
+>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 223, 36))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 223, 36))
+>PropertyName : Symbol(PropertyName, Decl(conditionalTypes2.ts, 224, 2))
+>RestrictToType : Symbol(RestrictToType, Decl(conditionalTypes2.ts, 223, 38))
+>PropertyName : Symbol(PropertyName, Decl(conditionalTypes2.ts, 224, 2))
+
+}[Extract<keyof T, string>];
+>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 223, 36))
+
+declare type GetAllPropertiesOfType<T, RestrictToType> = Pick<
+>GetAllPropertiesOfType : Symbol(GetAllPropertiesOfType, Decl(conditionalTypes2.ts, 225, 28))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 227, 36))
+>RestrictToType : Symbol(RestrictToType, Decl(conditionalTypes2.ts, 227, 38))
+>Pick : Symbol(Pick, Decl(lib.es5.d.ts, --, --))
+
+	T,
+>T : Symbol(T, Decl(conditionalTypes2.ts, 227, 36))
+
+	GetPropertyNamesOfType<Required<T>, RestrictToType>
+>GetPropertyNamesOfType : Symbol(GetPropertyNamesOfType, Decl(conditionalTypes2.ts, 221, 2))
+>Required : Symbol(Required, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 227, 36))
+>RestrictToType : Symbol(RestrictToType, Decl(conditionalTypes2.ts, 227, 38))
+
+>;
+
+// Repro from #33568
+
+declare function ff(x: Foo3<string>): void;
+>ff : Symbol(ff, Decl(conditionalTypes2.ts, 230, 2))
+>x : Symbol(x, Decl(conditionalTypes2.ts, 234, 20))
+>Foo3 : Symbol(Foo3, Decl(conditionalTypes2.ts, 235, 54))
+
+declare function gg<T>(f: (x: Foo3<T>) => void): void;
+>gg : Symbol(gg, Decl(conditionalTypes2.ts, 234, 43))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 235, 20))
+>f : Symbol(f, Decl(conditionalTypes2.ts, 235, 23))
+>x : Symbol(x, Decl(conditionalTypes2.ts, 235, 27))
+>Foo3 : Symbol(Foo3, Decl(conditionalTypes2.ts, 235, 54))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 235, 20))
+
+type Foo3<T> = T extends number ? { n: T } : { x: T };
+>Foo3 : Symbol(Foo3, Decl(conditionalTypes2.ts, 235, 54))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 236, 10))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 236, 10))
+>n : Symbol(n, Decl(conditionalTypes2.ts, 236, 35))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 236, 10))
+>x : Symbol(x, Decl(conditionalTypes2.ts, 236, 46))
+>T : Symbol(T, Decl(conditionalTypes2.ts, 236, 10))
+
+gg(ff);
+>gg : Symbol(gg, Decl(conditionalTypes2.ts, 234, 43))
+>ff : Symbol(ff, Decl(conditionalTypes2.ts, 230, 2))
+
diff --git a/tests/baselines/reference/conditionalTypes2.types b/tests/baselines/reference/conditionalTypes2.types
diff --git a/tests/cases/conformance/types/conditional/conditionalTypes2.ts b/tests/cases/conformance/types/conditional/conditionalTypes2.ts

Original file line number	Diff line number	Diff line change
`@@ -17552,9 +17552,12 @@ namespace ts {`
`17552`	`17552`	`inferFromTypes(getTrueTypeFromConditionalType(<ConditionalType>source), getTrueTypeFromConditionalType(<ConditionalType>target));`
`17553`	`17553`	`inferFromTypes(getFalseTypeFromConditionalType(<ConditionalType>source), getFalseTypeFromConditionalType(<ConditionalType>target));`
`17554`	`17554`	`}`
`17555`		`- else if (target.flags & TypeFlags.Conditional && !contravariant) {`
	`17555`	`+ else if (target.flags & TypeFlags.Conditional) {`
	`17556`	`+ const savePriority = priority;`
	`17557`	`+ priority \|= contravariant ? InferencePriority.ContravariantConditional : 0;`
`17556`	`17558`	`const targetTypes = [getTrueTypeFromConditionalType(<ConditionalType>target), getFalseTypeFromConditionalType(<ConditionalType>target)];`
`17557`	`17559`	`inferToMultipleTypes(source, targetTypes, target.flags);`
	`17560`	`+ priority = savePriority;`
`17558`	`17561`	`}`
`17559`	`17562`	`else if (target.flags & TypeFlags.UnionOrIntersection) {`
`17560`	`17563`	`inferToMultipleTypes(source, (<UnionOrIntersectionType>target).types, target.flags);`