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Expand exception to contravariant constraint elision to all type variables #43599

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Merged
merged 3 commits into from
Apr 14, 2021
Merged

Expand exception to contravariant constraint elision to all type variables #43599

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73d37f3
Expand exception to contravariant constraint elision to all type vari…
weswigham Apr 8, 2021
98efc1c
Comment update
weswigham Apr 14, 2021
80e8927
Merge branch 'master' into typevariable-carveout
weswigham Apr 14, 2021
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4 changes: 2 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12929,8 +12929,8 @@ namespace ts {
covariant = !covariant;
}
// Always substitute on type parameters, regardless of variance, since even
// in contravarrying positions, they may be reliant on subtuted constraints to be valid
if ((covariant || type.flags & TypeFlags.TypeParameter) && parent.kind === SyntaxKind.ConditionalType && node === (<ConditionalTypeNode>parent).trueType) {
// in contravariant positions, they may rely on substituted constraints to be valid
if ((covariant || type.flags & TypeFlags.TypeVariable) && parent.kind === SyntaxKind.ConditionalType && node === (<ConditionalTypeNode>parent).trueType) {
const constraint = getImpliedConstraint(type, (<ConditionalTypeNode>parent).checkType, (<ConditionalTypeNode>parent).extendsType);
if (constraint) {
constraints = append(constraints, constraint);
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11 changes: 10 additions & 1 deletion tests/baselines/reference/callOfConditionalTypeWithConcreteBranches.js
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Expand Up @@ -32,9 +32,18 @@ fn2<number>(m => m(42));
// webidl-conversions example where substituion must occur, despite contravariance of the position
// due to the invariant usage in `Parameters`

type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;
type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;

// vscode - another `Parameters` example
export type AddFirstParameterToFunctions<Target> = {
[K in keyof Target]: Target[K] extends (...args: any[]) => void
? (...args: Parameters<Target[K]>) => void
: void
};

//// [callOfConditionalTypeWithConcreteBranches.js]
"use strict";
exports.__esModule = true;
function fn(arg) {
// Expected: OK
// Actual: Cannot convert 10 to number & T
Expand Down
20 changes: 20 additions & 0 deletions tests/baselines/reference/callOfConditionalTypeWithConcreteBranches.symbols
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Expand Up @@ -103,3 +103,23 @@ type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void
>V : Symbol(V, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 7))
>Function : Symbol(Function, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

// vscode - another `Parameters` example
export type AddFirstParameterToFunctions<Target> = {
>AddFirstParameterToFunctions : Symbol(AddFirstParameterToFunctions, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 92))
>Target : Symbol(Target, Decl(callOfConditionalTypeWithConcreteBranches.ts, 36, 41))

[K in keyof Target]: Target[K] extends (...args: any[]) => void
>K : Symbol(K, Decl(callOfConditionalTypeWithConcreteBranches.ts, 37, 3))
>Target : Symbol(Target, Decl(callOfConditionalTypeWithConcreteBranches.ts, 36, 41))
>Target : Symbol(Target, Decl(callOfConditionalTypeWithConcreteBranches.ts, 36, 41))
>K : Symbol(K, Decl(callOfConditionalTypeWithConcreteBranches.ts, 37, 3))
>args : Symbol(args, Decl(callOfConditionalTypeWithConcreteBranches.ts, 37, 42))

? (...args: Parameters<Target[K]>) => void
>args : Symbol(args, Decl(callOfConditionalTypeWithConcreteBranches.ts, 38, 9))
>Parameters : Symbol(Parameters, Decl(lib.es5.d.ts, --, --))
>Target : Symbol(Target, Decl(callOfConditionalTypeWithConcreteBranches.ts, 36, 41))
>K : Symbol(K, Decl(callOfConditionalTypeWithConcreteBranches.ts, 37, 3))

: void
};
12 changes: 12 additions & 0 deletions tests/baselines/reference/callOfConditionalTypeWithConcreteBranches.types
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Expand Up @@ -97,3 +97,15 @@ type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void
>args : any[]
>args : Parameters<V>

// vscode - another `Parameters` example
export type AddFirstParameterToFunctions<Target> = {
>AddFirstParameterToFunctions : AddFirstParameterToFunctions<Target>

[K in keyof Target]: Target[K] extends (...args: any[]) => void
>args : any[]

? (...args: Parameters<Target[K]>) => void
>args : Parameters<Target[K]>

: void
};
9 changes: 8 additions & 1 deletion tests/cases/compiler/callOfConditionalTypeWithConcreteBranches.ts
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Expand Up @@ -31,4 +31,11 @@ fn2<number>(m => m(42));
// webidl-conversions example where substituion must occur, despite contravariance of the position
// due to the invariant usage in `Parameters`

type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;
type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;

// vscode - another `Parameters` example
export type AddFirstParameterToFunctions<Target> = {
[K in keyof Target]: Target[K] extends (...args: any[]) => void
? (...args: Parameters<Target[K]>) => void
: void
};