Improve logic that chooses co- vs. contra-variant inferences

src/compiler/checker.ts

@@ -26339,12 +26339,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     // all co-variant inferences are subtypes of it (i.e. it isn't one of a conflicting set of candidates), it is
                     // a subtype of some contra-variant inference, and no other type parameter is constrained to this type parameter
                     // and has inferences that would conflict. Otherwise, we prefer the contra-variant inference.
+                    // Similarly ignore co-variant `any` inference when both are available as almost everything is assignable to it
+                    // and it would spoil the overall inference.
                     const preferCovariantType = inferredCovariantType && (!inferredContravariantType ||
-                        !(inferredCovariantType.flags & TypeFlags.Never) &&
-                            some(inference.contraCandidates, t => isTypeSubtypeOf(inferredCovariantType, t)) &&
+                        !(inferredCovariantType.flags & (TypeFlags.Never | TypeFlags.Any)) &&
+                            some(inference.contraCandidates, t => isTypeAssignableTo(inferredCovariantType, t)) &&
                             every(context.inferences, other =>
                                 other !== inference && getConstraintOfTypeParameter(other.typeParameter) !== inference.typeParameter ||
-                                every(other.candidates, t => isTypeSubtypeOf(t, inferredCovariantType))));
+                                every(other.candidates, t => isTypeAssignableTo(t, inferredCovariantType))));
                     inferredType = preferCovariantType ? inferredCovariantType : inferredContravariantType;
                     fallbackType = preferCovariantType ? inferredContravariantType : inferredCovariantType;
                 }

tests/baselines/reference/coAndContraVariantInferences7.symbols

@@ -0,0 +1,77 @@
+//// [tests/cases/compiler/coAndContraVariantInferences7.ts] ////
+
+=== coAndContraVariantInferences7.ts ===
+type Request<TSchema extends Schema> = {
+>Request : Symbol(Request, Decl(coAndContraVariantInferences7.ts, 0, 0))
+>TSchema : Symbol(TSchema, Decl(coAndContraVariantInferences7.ts, 0, 13))
+>Schema : Symbol(Schema, Decl(coAndContraVariantInferences7.ts, 2, 2))
+
+  query: TSchema["query"];
+>query : Symbol(query, Decl(coAndContraVariantInferences7.ts, 0, 40))
+>TSchema : Symbol(TSchema, Decl(coAndContraVariantInferences7.ts, 0, 13))
+
+};
+
+type Schema = { query?: unknown; body?: unknown };
+>Schema : Symbol(Schema, Decl(coAndContraVariantInferences7.ts, 2, 2))
+>query : Symbol(query, Decl(coAndContraVariantInferences7.ts, 4, 15))
+>body : Symbol(body, Decl(coAndContraVariantInferences7.ts, 4, 32))
+
+declare function route<TSchema extends Schema>(obj: {
+>route : Symbol(route, Decl(coAndContraVariantInferences7.ts, 4, 50))
+>TSchema : Symbol(TSchema, Decl(coAndContraVariantInferences7.ts, 6, 23))
+>Schema : Symbol(Schema, Decl(coAndContraVariantInferences7.ts, 2, 2))
+>obj : Symbol(obj, Decl(coAndContraVariantInferences7.ts, 6, 47))
+
+  pre: (a: TSchema) => void;
+>pre : Symbol(pre, Decl(coAndContraVariantInferences7.ts, 6, 53))
+>a : Symbol(a, Decl(coAndContraVariantInferences7.ts, 7, 8))
+>TSchema : Symbol(TSchema, Decl(coAndContraVariantInferences7.ts, 6, 23))
+
+  schema: TSchema;
+>schema : Symbol(schema, Decl(coAndContraVariantInferences7.ts, 7, 28))
+>TSchema : Symbol(TSchema, Decl(coAndContraVariantInferences7.ts, 6, 23))
+
+  handle: (req: Request<TSchema>) => void;
+>handle : Symbol(handle, Decl(coAndContraVariantInferences7.ts, 8, 18))
+>req : Symbol(req, Decl(coAndContraVariantInferences7.ts, 9, 11))
+>Request : Symbol(Request, Decl(coAndContraVariantInferences7.ts, 0, 0))
+>TSchema : Symbol(TSchema, Decl(coAndContraVariantInferences7.ts, 6, 23))
+
+}): void;
+
+const validate = (_: { query?: unknown; body?: unknown }) => {};
+>validate : Symbol(validate, Decl(coAndContraVariantInferences7.ts, 12, 5))
+>_ : Symbol(_, Decl(coAndContraVariantInferences7.ts, 12, 18))
+>query : Symbol(query, Decl(coAndContraVariantInferences7.ts, 12, 22))
+>body : Symbol(body, Decl(coAndContraVariantInferences7.ts, 12, 39))
+
+route({
+>route : Symbol(route, Decl(coAndContraVariantInferences7.ts, 4, 50))
+
+  pre: validate,
+>pre : Symbol(pre, Decl(coAndContraVariantInferences7.ts, 14, 7))
+>validate : Symbol(validate, Decl(coAndContraVariantInferences7.ts, 12, 5))
+
+  schema: {
+>schema : Symbol(schema, Decl(coAndContraVariantInferences7.ts, 15, 16))
+
+    query: "",
+>query : Symbol(query, Decl(coAndContraVariantInferences7.ts, 16, 11))
+
+  },
+  handle: (req) => {
+>handle : Symbol(handle, Decl(coAndContraVariantInferences7.ts, 18, 4))
+>req : Symbol(req, Decl(coAndContraVariantInferences7.ts, 19, 11))
+
+    const test: string = req.query;
+>test : Symbol(test, Decl(coAndContraVariantInferences7.ts, 20, 9))
+>req.query : Symbol(query, Decl(coAndContraVariantInferences7.ts, 0, 40))
+>req : Symbol(req, Decl(coAndContraVariantInferences7.ts, 19, 11))
+>query : Symbol(query, Decl(coAndContraVariantInferences7.ts, 0, 40))
+
+  },
+});
+
+export {};
+

tests/baselines/reference/coAndContraVariantInferences7.types

@@ -0,0 +1,107 @@
+//// [tests/cases/compiler/coAndContraVariantInferences7.ts] ////
+
+=== coAndContraVariantInferences7.ts ===
+type Request<TSchema extends Schema> = {
+>Request : Request<TSchema>
+>        : ^^^^^^^^^^^^^^^^
+
+  query: TSchema["query"];
+>query : TSchema["query"]
+>      : ^^^^^^^^^^^^^^^^
+
+};
+
+type Schema = { query?: unknown; body?: unknown };
+>Schema : Schema
+>       : ^^^^^^
+>query : unknown
+>      : ^^^^^^^
+>body : unknown
+>     : ^^^^^^^
+
+declare function route<TSchema extends Schema>(obj: {
+>route : <TSchema extends Schema>(obj: { pre: (a: TSchema) => void; schema: TSchema; handle: (req: Request<TSchema>) => void; }) => void
+>      : ^       ^^^^^^^^^^^^^^^^^   ^^                                                                                        ^^^^^    
+>obj : { pre: (a: TSchema) => void; schema: TSchema; handle: (req: Request<TSchema>) => void; }
+>    : ^^^^^^^                    ^^^^^^^^^^       ^^^^^^^^^^                               ^^^
+
+  pre: (a: TSchema) => void;
+>pre : (a: TSchema) => void
+>    : ^ ^^       ^^^^^    
+>a : TSchema
+>  : ^^^^^^^
+
+  schema: TSchema;
+>schema : TSchema
+>       : ^^^^^^^
+
+  handle: (req: Request<TSchema>) => void;
+>handle : (req: Request<TSchema>) => void
+>       : ^   ^^                ^^^^^    
+>req : Request<TSchema>
+>    : ^^^^^^^^^^^^^^^^
+
+}): void;
+
+const validate = (_: { query?: unknown; body?: unknown }) => {};
+>validate : (_: { query?: unknown; body?: unknown; }) => void
+>         : ^ ^^                                    ^^^^^^^^^
+>(_: { query?: unknown; body?: unknown }) => {} : (_: { query?: unknown; body?: unknown; }) => void
+>                                               : ^ ^^                                    ^^^^^^^^^
+>_ : { query?: unknown; body?: unknown; }
+>  : ^^^^^^^^^^       ^^^^^^^^^       ^^^
+>query : unknown
+>      : ^^^^^^^
+>body : unknown
+>     : ^^^^^^^
+
+route({
+>route({  pre: validate,  schema: {    query: "",  },  handle: (req) => {    const test: string = req.query;  },}) : void
+>                                                                                                                  : ^^^^
+>route : <TSchema extends Schema>(obj: { pre: (a: TSchema) => void; schema: TSchema; handle: (req: Request<TSchema>) => void; }) => void
+>      : ^       ^^^^^^^^^^^^^^^^^   ^^                                                                                        ^^^^^^^^^
+>{  pre: validate,  schema: {    query: "",  },  handle: (req) => {    const test: string = req.query;  },} : { pre: (_: { query?: unknown; body?: unknown; }) => void; schema: { query: string; }; handle: (req: Request<{ query: string; }>) => void; }
+>                                                                                                           : ^^^^^^^^ ^^                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+  pre: validate,
+>pre : (_: { query?: unknown; body?: unknown; }) => void
+>    : ^ ^^                                    ^^^^^^^^^
+>validate : (_: { query?: unknown; body?: unknown; }) => void
+>         : ^ ^^                                    ^^^^^^^^^
+
+  schema: {
+>schema : { query: string; }
+>       : ^^^^^^^^^^^^^^^^^^
+>{    query: "",  } : { query: string; }
+>                   : ^^^^^^^^^^^^^^^^^^
+
+    query: "",
+>query : string
+>      : ^^^^^^
+>"" : ""
+>   : ^^
+
+  },
+  handle: (req) => {
+>handle : (req: Request<{ query: string; }>) => void
+>       : ^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>(req) => {    const test: string = req.query;  } : (req: Request<{ query: string; }>) => void
+>                                                 : ^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>req : Request<{ query: string; }>
+>    : ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    const test: string = req.query;
+>test : string
+>     : ^^^^^^
+>req.query : string
+>          : ^^^^^^
+>req : Request<{ query: string; }>
+>    : ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>query : string
+>      : ^^^^^^
+
+  },
+});
+
+export {};
+

tests/baselines/reference/coAndContraVariantInferences8.symbols

@@ -0,0 +1,29 @@
+//// [tests/cases/compiler/coAndContraVariantInferences8.ts] ////
+
+=== coAndContraVariantInferences8.ts ===
+// https://github.com/microsoft/TypeScript/issues/58468
+
+declare const fn: (() => void) | ((a: number) => void);
+>fn : Symbol(fn, Decl(coAndContraVariantInferences8.ts, 2, 13))
+>a : Symbol(a, Decl(coAndContraVariantInferences8.ts, 2, 35))
+
+declare const x: number;
+>x : Symbol(x, Decl(coAndContraVariantInferences8.ts, 4, 13))
+
+declare const y: any;
+>y : Symbol(y, Decl(coAndContraVariantInferences8.ts, 5, 13))
+
+fn.call(null, x);
+>fn.call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
+>fn : Symbol(fn, Decl(coAndContraVariantInferences8.ts, 2, 13))
+>call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(coAndContraVariantInferences8.ts, 4, 13))
+
+fn.call(null, y);
+>fn.call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
+>fn : Symbol(fn, Decl(coAndContraVariantInferences8.ts, 2, 13))
+>call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
+>y : Symbol(y, Decl(coAndContraVariantInferences8.ts, 5, 13))
+
+export {};
+

tests/baselines/reference/coAndContraVariantInferences8.types

@@ -0,0 +1,43 @@
+//// [tests/cases/compiler/coAndContraVariantInferences8.ts] ////
+
+=== coAndContraVariantInferences8.ts ===
+// https://github.com/microsoft/TypeScript/issues/58468
+
+declare const fn: (() => void) | ((a: number) => void);
+>fn : (() => void) | ((a: number) => void)
+>   : ^^^^^^^    ^^^^^^ ^^      ^^^^^    ^
+>a : number
+>  : ^^^^^^
+
+declare const x: number;
+>x : number
+>  : ^^^^^^
+
+declare const y: any;
+>y : any
+
+fn.call(null, x);
+>fn.call(null, x) : void
+>                 : ^^^^
+>fn.call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
+>        : ^ ^^ ^^^^^^^^^^^^^^^^ ^^    ^^                          ^^       ^^ ^^^^^    ^^ ^^^^^^
+>fn : (() => void) | ((a: number) => void)
+>   : ^^^^^^^^^^^^^^^^^ ^^      ^^^^^^^^^^
+>call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
+>     : ^ ^^ ^^^^^^^^^^^^^^^^ ^^    ^^                          ^^       ^^ ^^^^^    ^^ ^^^^^^
+>x : number
+>  : ^^^^^^
+
+fn.call(null, y);
+>fn.call(null, y) : void
+>                 : ^^^^
+>fn.call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
+>        : ^ ^^ ^^^^^^^^^^^^^^^^ ^^    ^^                          ^^       ^^ ^^^^^    ^^ ^^^^^^
+>fn : (() => void) | ((a: number) => void)
+>   : ^^^^^^^^^^^^^^^^^ ^^      ^^^^^^^^^^
+>call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
+>     : ^ ^^ ^^^^^^^^^^^^^^^^ ^^    ^^                          ^^       ^^ ^^^^^    ^^ ^^^^^^
+>y : any
+
+export {};
+

tests/cases/compiler/coAndContraVariantInferences7.ts

@@ -0,0 +1,28 @@
+// @strict: true
+// @noEmit: true
+
+type Request<TSchema extends Schema> = {
+  query: TSchema["query"];
+};
+
+type Schema = { query?: unknown; body?: unknown };
+
+declare function route<TSchema extends Schema>(obj: {
+  pre: (a: TSchema) => void;
+  schema: TSchema;
+  handle: (req: Request<TSchema>) => void;
+}): void;
+
+const validate = (_: { query?: unknown; body?: unknown }) => {};
+
+route({
+  pre: validate,
+  schema: {
+    query: "",
+  },
+  handle: (req) => {
+    const test: string = req.query;
+  },
+});
+
+export {};

tests/cases/compiler/coAndContraVariantInferences8.ts

@@ -0,0 +1,14 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/TypeScript/issues/58468
+
+declare const fn: (() => void) | ((a: number) => void);
+
+declare const x: number;
+declare const y: any;
+
+fn.call(null, x);
+fn.call(null, y);
+
+export {};