Improve logic for choosing between co- and contra-variant inferences

src/compiler/checker.ts

@@ -22329,12 +22329,11 @@ namespace ts {
                 if (signature) {
                     const inferredCovariantType = inference.candidates ? getCovariantInference(inference, signature) : undefined;
                     if (inference.contraCandidates) {
-                        const inferredContravariantType = getContravariantInference(inference);
                         // If we have both co- and contra-variant inferences, we prefer the contra-variant inference
-                        // unless the co-variant inference is a subtype and not 'never'.
+                        // unless the co-variant inference is a subtype of some contra-variant inference and not 'never'.
                         inferredType = inferredCovariantType && !(inferredCovariantType.flags & TypeFlags.Never) &&
-                            isTypeSubtypeOf(inferredCovariantType, inferredContravariantType) ?
-                            inferredCovariantType : inferredContravariantType;
+                            some(inference.contraCandidates, t => isTypeSubtypeOf(inferredCovariantType, t)) ?
+                            inferredCovariantType : getContravariantInference(inference);
                     }
                     else if (inferredCovariantType) {
                         inferredType = inferredCovariantType;

tests/baselines/reference/coAndContraVariantInferences.js

@@ -0,0 +1,74 @@
+//// [coAndContraVariantInferences.ts]
+type A = { kind: 'a' };
+type B = { kind: 'b' };
+
+declare const a: A;
+declare const b: B;
+
+declare function fab(arg: A | B): void;
+
+declare function foo<T>(x: { kind: T }, f: (arg: { kind: T }) => void): void;
+
+foo(a, fab);
+foo(b, fab);
+
+// Repro from #45603
+
+interface Action<TName extends string,TPayload> {
+    name: TName,
+    payload: TPayload
+}
+
+const actionA = { payload: 'any-string' } as Action<'ACTION_A', string>;
+const actionB = { payload: true } as Action<'ACTION_B', boolean>;
+
+function call<TName extends string,TPayload>(
+  action: Action<TName,TPayload>,
+  fn: (action: Action<TName,TPayload>)=> any,
+) {
+  fn(action);
+}
+
+const printFn = (action: typeof actionA | typeof actionB)=> console.log(action);
+
+call(actionA, printFn);
+call(actionB, printFn);
+
+
+//// [coAndContraVariantInferences.js]
+"use strict";
+foo(a, fab);
+foo(b, fab);
+var actionA = { payload: 'any-string' };
+var actionB = { payload: true };
+function call(action, fn) {
+    fn(action);
+}
+var printFn = function (action) { return console.log(action); };
+call(actionA, printFn);
+call(actionB, printFn);
+
+
+//// [coAndContraVariantInferences.d.ts]
+declare type A = {
+    kind: 'a';
+};
+declare type B = {
+    kind: 'b';
+};
+declare const a: A;
+declare const b: B;
+declare function fab(arg: A | B): void;
+declare function foo<T>(x: {
+    kind: T;
+}, f: (arg: {
+    kind: T;
+}) => void): void;
+interface Action<TName extends string, TPayload> {
+    name: TName;
+    payload: TPayload;
+}
+declare const actionA: Action<"ACTION_A", string>;
+declare const actionB: Action<"ACTION_B", boolean>;
+declare function call<TName extends string, TPayload>(action: Action<TName, TPayload>, fn: (action: Action<TName, TPayload>) => any): void;
+declare const printFn: (action: typeof actionA | typeof actionB) => void;

tests/baselines/reference/coAndContraVariantInferences.symbols

@@ -0,0 +1,114 @@
+=== tests/cases/compiler/coAndContraVariantInferences.ts ===
+type A = { kind: 'a' };
+>A : Symbol(A, Decl(coAndContraVariantInferences.ts, 0, 0))
+>kind : Symbol(kind, Decl(coAndContraVariantInferences.ts, 0, 10))
+
+type B = { kind: 'b' };
+>B : Symbol(B, Decl(coAndContraVariantInferences.ts, 0, 23))
+>kind : Symbol(kind, Decl(coAndContraVariantInferences.ts, 1, 10))
+
+declare const a: A;
+>a : Symbol(a, Decl(coAndContraVariantInferences.ts, 3, 13))
+>A : Symbol(A, Decl(coAndContraVariantInferences.ts, 0, 0))
+
+declare const b: B;
+>b : Symbol(b, Decl(coAndContraVariantInferences.ts, 4, 13))
+>B : Symbol(B, Decl(coAndContraVariantInferences.ts, 0, 23))
+
+declare function fab(arg: A | B): void;
+>fab : Symbol(fab, Decl(coAndContraVariantInferences.ts, 4, 19))
+>arg : Symbol(arg, Decl(coAndContraVariantInferences.ts, 6, 21))
+>A : Symbol(A, Decl(coAndContraVariantInferences.ts, 0, 0))
+>B : Symbol(B, Decl(coAndContraVariantInferences.ts, 0, 23))
+
+declare function foo<T>(x: { kind: T }, f: (arg: { kind: T }) => void): void;
+>foo : Symbol(foo, Decl(coAndContraVariantInferences.ts, 6, 39))
+>T : Symbol(T, Decl(coAndContraVariantInferences.ts, 8, 21))
+>x : Symbol(x, Decl(coAndContraVariantInferences.ts, 8, 24))
+>kind : Symbol(kind, Decl(coAndContraVariantInferences.ts, 8, 28))
+>T : Symbol(T, Decl(coAndContraVariantInferences.ts, 8, 21))
+>f : Symbol(f, Decl(coAndContraVariantInferences.ts, 8, 39))
+>arg : Symbol(arg, Decl(coAndContraVariantInferences.ts, 8, 44))
+>kind : Symbol(kind, Decl(coAndContraVariantInferences.ts, 8, 50))
+>T : Symbol(T, Decl(coAndContraVariantInferences.ts, 8, 21))
+
+foo(a, fab);
+>foo : Symbol(foo, Decl(coAndContraVariantInferences.ts, 6, 39))
+>a : Symbol(a, Decl(coAndContraVariantInferences.ts, 3, 13))
+>fab : Symbol(fab, Decl(coAndContraVariantInferences.ts, 4, 19))
+
+foo(b, fab);
+>foo : Symbol(foo, Decl(coAndContraVariantInferences.ts, 6, 39))
+>b : Symbol(b, Decl(coAndContraVariantInferences.ts, 4, 13))
+>fab : Symbol(fab, Decl(coAndContraVariantInferences.ts, 4, 19))
+
+// Repro from #45603
+
+interface Action<TName extends string,TPayload> {
+>Action : Symbol(Action, Decl(coAndContraVariantInferences.ts, 11, 12))
+>TName : Symbol(TName, Decl(coAndContraVariantInferences.ts, 15, 17))
+>TPayload : Symbol(TPayload, Decl(coAndContraVariantInferences.ts, 15, 38))
+
+    name: TName,
+>name : Symbol(Action.name, Decl(coAndContraVariantInferences.ts, 15, 49))
+>TName : Symbol(TName, Decl(coAndContraVariantInferences.ts, 15, 17))
+
+    payload: TPayload
+>payload : Symbol(Action.payload, Decl(coAndContraVariantInferences.ts, 16, 16))
+>TPayload : Symbol(TPayload, Decl(coAndContraVariantInferences.ts, 15, 38))
+}
+
+const actionA = { payload: 'any-string' } as Action<'ACTION_A', string>;
+>actionA : Symbol(actionA, Decl(coAndContraVariantInferences.ts, 20, 5))
+>payload : Symbol(payload, Decl(coAndContraVariantInferences.ts, 20, 17))
+>Action : Symbol(Action, Decl(coAndContraVariantInferences.ts, 11, 12))
+
+const actionB = { payload: true } as Action<'ACTION_B', boolean>;
+>actionB : Symbol(actionB, Decl(coAndContraVariantInferences.ts, 21, 5))
+>payload : Symbol(payload, Decl(coAndContraVariantInferences.ts, 21, 17))
+>Action : Symbol(Action, Decl(coAndContraVariantInferences.ts, 11, 12))
+
+function call<TName extends string,TPayload>(
+>call : Symbol(call, Decl(coAndContraVariantInferences.ts, 21, 65))
+>TName : Symbol(TName, Decl(coAndContraVariantInferences.ts, 23, 14))
+>TPayload : Symbol(TPayload, Decl(coAndContraVariantInferences.ts, 23, 35))
+
+  action: Action<TName,TPayload>,
+>action : Symbol(action, Decl(coAndContraVariantInferences.ts, 23, 45))
+>Action : Symbol(Action, Decl(coAndContraVariantInferences.ts, 11, 12))
+>TName : Symbol(TName, Decl(coAndContraVariantInferences.ts, 23, 14))
+>TPayload : Symbol(TPayload, Decl(coAndContraVariantInferences.ts, 23, 35))
+
+  fn: (action: Action<TName,TPayload>)=> any,
+>fn : Symbol(fn, Decl(coAndContraVariantInferences.ts, 24, 33))
+>action : Symbol(action, Decl(coAndContraVariantInferences.ts, 25, 7))
+>Action : Symbol(Action, Decl(coAndContraVariantInferences.ts, 11, 12))
+>TName : Symbol(TName, Decl(coAndContraVariantInferences.ts, 23, 14))
+>TPayload : Symbol(TPayload, Decl(coAndContraVariantInferences.ts, 23, 35))
+
+) {
+  fn(action);
+>fn : Symbol(fn, Decl(coAndContraVariantInferences.ts, 24, 33))
+>action : Symbol(action, Decl(coAndContraVariantInferences.ts, 23, 45))
+}
+
+const printFn = (action: typeof actionA | typeof actionB)=> console.log(action);
+>printFn : Symbol(printFn, Decl(coAndContraVariantInferences.ts, 30, 5))
+>action : Symbol(action, Decl(coAndContraVariantInferences.ts, 30, 17))
+>actionA : Symbol(actionA, Decl(coAndContraVariantInferences.ts, 20, 5))
+>actionB : Symbol(actionB, Decl(coAndContraVariantInferences.ts, 21, 5))
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>action : Symbol(action, Decl(coAndContraVariantInferences.ts, 30, 17))
+
+call(actionA, printFn);
+>call : Symbol(call, Decl(coAndContraVariantInferences.ts, 21, 65))
+>actionA : Symbol(actionA, Decl(coAndContraVariantInferences.ts, 20, 5))
+>printFn : Symbol(printFn, Decl(coAndContraVariantInferences.ts, 30, 5))
+
+call(actionB, printFn);
+>call : Symbol(call, Decl(coAndContraVariantInferences.ts, 21, 65))
+>actionB : Symbol(actionB, Decl(coAndContraVariantInferences.ts, 21, 5))
+>printFn : Symbol(printFn, Decl(coAndContraVariantInferences.ts, 30, 5))
+

tests/baselines/reference/coAndContraVariantInferences.types

@@ -0,0 +1,104 @@
+=== tests/cases/compiler/coAndContraVariantInferences.ts ===
+type A = { kind: 'a' };
+>A : A
+>kind : "a"
+
+type B = { kind: 'b' };
+>B : B
+>kind : "b"
+
+declare const a: A;
+>a : A
+
+declare const b: B;
+>b : B
+
+declare function fab(arg: A | B): void;
+>fab : (arg: A | B) => void
+>arg : A | B
+
+declare function foo<T>(x: { kind: T }, f: (arg: { kind: T }) => void): void;
+>foo : <T>(x: {    kind: T;}, f: (arg: {    kind: T;}) => void) => void
+>x : { kind: T; }
+>kind : T
+>f : (arg: {    kind: T;}) => void
+>arg : { kind: T; }
+>kind : T
+
+foo(a, fab);
+>foo(a, fab) : void
+>foo : <T>(x: { kind: T; }, f: (arg: { kind: T; }) => void) => void
+>a : A
+>fab : (arg: A | B) => void
+
+foo(b, fab);
+>foo(b, fab) : void
+>foo : <T>(x: { kind: T; }, f: (arg: { kind: T; }) => void) => void
+>b : B
+>fab : (arg: A | B) => void
+
+// Repro from #45603
+
+interface Action<TName extends string,TPayload> {
+    name: TName,
+>name : TName
+
+    payload: TPayload
+>payload : TPayload
+}
+
+const actionA = { payload: 'any-string' } as Action<'ACTION_A', string>;
+>actionA : Action<"ACTION_A", string>
+>{ payload: 'any-string' } as Action<'ACTION_A', string> : Action<"ACTION_A", string>
+>{ payload: 'any-string' } : { payload: string; }
+>payload : string
+>'any-string' : "any-string"
+
+const actionB = { payload: true } as Action<'ACTION_B', boolean>;
+>actionB : Action<"ACTION_B", boolean>
+>{ payload: true } as Action<'ACTION_B', boolean> : Action<"ACTION_B", boolean>
+>{ payload: true } : { payload: true; }
+>payload : true
+>true : true
+
+function call<TName extends string,TPayload>(
+>call : <TName extends string, TPayload>(action: Action<TName, TPayload>, fn: (action: Action<TName, TPayload>) => any) => void
+
+  action: Action<TName,TPayload>,
+>action : Action<TName, TPayload>
+
+  fn: (action: Action<TName,TPayload>)=> any,
+>fn : (action: Action<TName, TPayload>) => any
+>action : Action<TName, TPayload>
+
+) {
+  fn(action);
+>fn(action) : any
+>fn : (action: Action<TName, TPayload>) => any
+>action : Action<TName, TPayload>
+}
+
+const printFn = (action: typeof actionA | typeof actionB)=> console.log(action);
+>printFn : (action: typeof actionA | typeof actionB) => void
+>(action: typeof actionA | typeof actionB)=> console.log(action) : (action: typeof actionA | typeof actionB) => void
+>action : Action<"ACTION_A", string> | Action<"ACTION_B", boolean>
+>actionA : Action<"ACTION_A", string>
+>actionB : Action<"ACTION_B", boolean>
+>console.log(action) : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>action : Action<"ACTION_A", string> | Action<"ACTION_B", boolean>
+
+call(actionA, printFn);
+>call(actionA, printFn) : void
+>call : <TName extends string, TPayload>(action: Action<TName, TPayload>, fn: (action: Action<TName, TPayload>) => any) => void
+>actionA : Action<"ACTION_A", string>
+>printFn : (action: Action<"ACTION_A", string> | Action<"ACTION_B", boolean>) => void
+
+call(actionB, printFn);
+>call(actionB, printFn) : void
+>call : <TName extends string, TPayload>(action: Action<TName, TPayload>, fn: (action: Action<TName, TPayload>) => any) => void
+>actionB : Action<"ACTION_B", boolean>
+>printFn : (action: Action<"ACTION_A", string> | Action<"ACTION_B", boolean>) => void
+

tests/cases/compiler/coAndContraVariantInferences.ts

@@ -0,0 +1,37 @@
+// @strict: true
+// @declaration: true
+
+type A = { kind: 'a' };
+type B = { kind: 'b' };
+
+declare const a: A;
+declare const b: B;
+
+declare function fab(arg: A | B): void;
+
+declare function foo<T>(x: { kind: T }, f: (arg: { kind: T }) => void): void;
+
+foo(a, fab);
+foo(b, fab);
+
+// Repro from #45603
+
+interface Action<TName extends string,TPayload> {
+    name: TName,
+    payload: TPayload
+}
+
+const actionA = { payload: 'any-string' } as Action<'ACTION_A', string>;
+const actionB = { payload: true } as Action<'ACTION_B', boolean>;
+
+function call<TName extends string,TPayload>(
+  action: Action<TName,TPayload>,
+  fn: (action: Action<TName,TPayload>)=> any,
+) {
+  fn(action);
+}
+
+const printFn = (action: typeof actionA | typeof actionB)=> console.log(action);
+
+call(actionA, printFn);
+call(actionB, printFn);