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ahejlsbergahejlsberg
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Merge pull request microsoft#31662 from microsoft/fixTypeAliasInference
Fix contravariant type alias inference
2 parents b8dcf27 + bb412ab commit 82ea885

5 files changed

Lines changed: 171 additions & 17 deletions

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‎src/compiler/checker.ts‎

Lines changed: 14 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -15171,11 +15171,7 @@ namespace ts {
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if (source.aliasSymbol && source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol) {
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// Source and target are types originating in the same generic type alias declaration.
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// Simply infer from source type arguments to target type arguments.
15174-
const sourceTypes = source.aliasTypeArguments;
15175-
const targetTypes = target.aliasTypeArguments!;
15176-
for (let i = 0; i < sourceTypes.length; i++) {
15177-
inferFromTypes(sourceTypes[i], targetTypes[i]);
15178-
}
15174+
inferFromTypeArguments(source.aliasTypeArguments, target.aliasTypeArguments!, getAliasVariances(source.aliasSymbol));
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return;
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}
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if (source.flags & TypeFlags.Union && target.flags & TypeFlags.Union && !(source.flags & TypeFlags.EnumLiteral && target.flags & TypeFlags.EnumLiteral) ||
@@ -15281,18 +15277,7 @@ namespace ts {
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}
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if (getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(target) & ObjectFlags.Reference && (<TypeReference>source).target === (<TypeReference>target).target) {
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// If source and target are references to the same generic type, infer from type arguments
15284-
const sourceTypes = (<TypeReference>source).typeArguments || emptyArray;
15285-
const targetTypes = (<TypeReference>target).typeArguments || emptyArray;
15286-
const count = sourceTypes.length < targetTypes.length ? sourceTypes.length : targetTypes.length;
15287-
const variances = getVariances((<TypeReference>source).target);
15288-
for (let i = 0; i < count; i++) {
15289-
if (i < variances.length && (variances[i] & VarianceFlags.VarianceMask) === VarianceFlags.Contravariant) {
15290-
inferFromContravariantTypes(sourceTypes[i], targetTypes[i]);
15291-
}
15292-
else {
15293-
inferFromTypes(sourceTypes[i], targetTypes[i]);
15294-
}
15295-
}
15280+
inferFromTypeArguments((<TypeReference>source).typeArguments || emptyArray, (<TypeReference>target).typeArguments || emptyArray, getVariances((<TypeReference>source).target));
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}
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else if (source.flags & TypeFlags.Index && target.flags & TypeFlags.Index) {
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contravariant = !contravariant;
@@ -15412,6 +15397,18 @@ namespace ts {
1541215397
}
1541315398
}
1541415399

15400+
function inferFromTypeArguments(sourceTypes: readonly Type[], targetTypes: readonly Type[], variances: readonly VarianceFlags[]) {
15401+
const count = sourceTypes.length < targetTypes.length ? sourceTypes.length : targetTypes.length;
15402+
for (let i = 0; i < count; i++) {
15403+
if (i < variances.length && (variances[i] & VarianceFlags.VarianceMask) === VarianceFlags.Contravariant) {
15404+
inferFromContravariantTypes(sourceTypes[i], targetTypes[i]);
15405+
}
15406+
else {
15407+
inferFromTypes(sourceTypes[i], targetTypes[i]);
15408+
}
15409+
}
15410+
}
15411+
1541515412
function inferFromContravariantTypes(source: Type, target: Type) {
1541615413
if (strictFunctionTypes || priority & InferencePriority.AlwaysStrict) {
1541715414
contravariant = !contravariant;

‎tests/baselines/reference/contravariantTypeAliasInference.js‎

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
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//// [contravariantTypeAliasInference.ts]
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type Func1<T> = (x: T) => void;
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type Func2<T> = ((x: T) => void) | undefined;
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declare let f1: Func1<string>;
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declare let f2: Func1<"a">;
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declare function foo<T>(f1: Func1<T>, f2: Func1<T>): void;
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foo(f1, f2);
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declare let g1: Func2<string>;
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declare let g2: Func2<"a">;
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declare function bar<T>(g1: Func2<T>, g2: Func2<T>): void;
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bar(f1, f2);
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bar(g1, g2);
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//// [contravariantTypeAliasInference.js]
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"use strict";
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foo(f1, f2);
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bar(f1, f2);
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bar(g1, g2);

‎tests/baselines/reference/contravariantTypeAliasInference.symbols‎

Lines changed: 64 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,64 @@
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=== tests/cases/compiler/contravariantTypeAliasInference.ts ===
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type Func1<T> = (x: T) => void;
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>Func1 : Symbol(Func1, Decl(contravariantTypeAliasInference.ts, 0, 0))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 0, 11))
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>x : Symbol(x, Decl(contravariantTypeAliasInference.ts, 0, 17))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 0, 11))
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type Func2<T> = ((x: T) => void) | undefined;
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>Func2 : Symbol(Func2, Decl(contravariantTypeAliasInference.ts, 0, 31))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 1, 11))
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>x : Symbol(x, Decl(contravariantTypeAliasInference.ts, 1, 18))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 1, 11))
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declare let f1: Func1<string>;
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>f1 : Symbol(f1, Decl(contravariantTypeAliasInference.ts, 3, 11))
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>Func1 : Symbol(Func1, Decl(contravariantTypeAliasInference.ts, 0, 0))
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18+
declare let f2: Func1<"a">;
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>f2 : Symbol(f2, Decl(contravariantTypeAliasInference.ts, 4, 11))
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>Func1 : Symbol(Func1, Decl(contravariantTypeAliasInference.ts, 0, 0))
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declare function foo<T>(f1: Func1<T>, f2: Func1<T>): void;
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>foo : Symbol(foo, Decl(contravariantTypeAliasInference.ts, 4, 27))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 6, 21))
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>f1 : Symbol(f1, Decl(contravariantTypeAliasInference.ts, 6, 24))
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>Func1 : Symbol(Func1, Decl(contravariantTypeAliasInference.ts, 0, 0))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 6, 21))
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>f2 : Symbol(f2, Decl(contravariantTypeAliasInference.ts, 6, 37))
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>Func1 : Symbol(Func1, Decl(contravariantTypeAliasInference.ts, 0, 0))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 6, 21))
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foo(f1, f2);
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>foo : Symbol(foo, Decl(contravariantTypeAliasInference.ts, 4, 27))
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>f1 : Symbol(f1, Decl(contravariantTypeAliasInference.ts, 3, 11))
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>f2 : Symbol(f2, Decl(contravariantTypeAliasInference.ts, 4, 11))
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declare let g1: Func2<string>;
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>g1 : Symbol(g1, Decl(contravariantTypeAliasInference.ts, 10, 11))
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>Func2 : Symbol(Func2, Decl(contravariantTypeAliasInference.ts, 0, 31))
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declare let g2: Func2<"a">;
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>g2 : Symbol(g2, Decl(contravariantTypeAliasInference.ts, 11, 11))
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>Func2 : Symbol(Func2, Decl(contravariantTypeAliasInference.ts, 0, 31))
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45+
declare function bar<T>(g1: Func2<T>, g2: Func2<T>): void;
46+
>bar : Symbol(bar, Decl(contravariantTypeAliasInference.ts, 11, 27))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 13, 21))
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>g1 : Symbol(g1, Decl(contravariantTypeAliasInference.ts, 13, 24))
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>Func2 : Symbol(Func2, Decl(contravariantTypeAliasInference.ts, 0, 31))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 13, 21))
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>g2 : Symbol(g2, Decl(contravariantTypeAliasInference.ts, 13, 37))
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>Func2 : Symbol(Func2, Decl(contravariantTypeAliasInference.ts, 0, 31))
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>T : Symbol(T, Decl(contravariantTypeAliasInference.ts, 13, 21))
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55+
bar(f1, f2);
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>bar : Symbol(bar, Decl(contravariantTypeAliasInference.ts, 11, 27))
57+
>f1 : Symbol(f1, Decl(contravariantTypeAliasInference.ts, 3, 11))
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>f2 : Symbol(f2, Decl(contravariantTypeAliasInference.ts, 4, 11))
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bar(g1, g2);
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>bar : Symbol(bar, Decl(contravariantTypeAliasInference.ts, 11, 27))
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>g1 : Symbol(g1, Decl(contravariantTypeAliasInference.ts, 10, 11))
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>g2 : Symbol(g2, Decl(contravariantTypeAliasInference.ts, 11, 11))
64+

‎tests/baselines/reference/contravariantTypeAliasInference.types‎

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@@ -0,0 +1,49 @@
1+
=== tests/cases/compiler/contravariantTypeAliasInference.ts ===
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type Func1<T> = (x: T) => void;
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>Func1 : Func1<T>
4+
>x : T
5+
6+
type Func2<T> = ((x: T) => void) | undefined;
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>Func2 : Func2<T>
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>x : T
9+
10+
declare let f1: Func1<string>;
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>f1 : Func1<string>
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declare let f2: Func1<"a">;
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>f2 : Func1<"a">
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16+
declare function foo<T>(f1: Func1<T>, f2: Func1<T>): void;
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>foo : <T>(f1: Func1<T>, f2: Func1<T>) => void
18+
>f1 : Func1<T>
19+
>f2 : Func1<T>
20+
21+
foo(f1, f2);
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>foo(f1, f2) : void
23+
>foo : <T>(f1: Func1<T>, f2: Func1<T>) => void
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>f1 : Func1<string>
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>f2 : Func1<"a">
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27+
declare let g1: Func2<string>;
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>g1 : Func2<string>
29+
30+
declare let g2: Func2<"a">;
31+
>g2 : Func2<"a">
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33+
declare function bar<T>(g1: Func2<T>, g2: Func2<T>): void;
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>bar : <T>(g1: Func2<T>, g2: Func2<T>) => void
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>g1 : Func2<T>
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>g2 : Func2<T>
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bar(f1, f2);
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>bar(f1, f2) : void
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>bar : <T>(g1: Func2<T>, g2: Func2<T>) => void
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>f1 : Func1<string>
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>f2 : Func1<"a">
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bar(g1, g2);
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>bar(g1, g2) : void
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>bar : <T>(g1: Func2<T>, g2: Func2<T>) => void
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>g1 : Func2<string>
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>g2 : Func2<"a">
49+

‎tests/cases/compiler/contravariantTypeAliasInference.ts‎

Lines changed: 19 additions & 0 deletions
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@@ -0,0 +1,19 @@
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// @strict: true
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type Func1<T> = (x: T) => void;
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type Func2<T> = ((x: T) => void) | undefined;
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declare let f1: Func1<string>;
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declare let f2: Func1<"a">;
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declare function foo<T>(f1: Func1<T>, f2: Func1<T>): void;
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foo(f1, f2);
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declare let g1: Func2<string>;
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declare let g2: Func2<"a">;
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declare function bar<T>(g1: Func2<T>, g2: Func2<T>): void;
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bar(f1, f2);
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bar(g1, g2);

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