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Only infer readonly tuples for const type parameters when constraints permit (#55229)

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Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>
This commit is contained in:
Anders Hejlsberg
2023-08-26 08:20:55 -07:00
committed by GitHub
parent 51e7a34c2c
commit 753c463821
6 changed files with 854 additions and 5 deletions
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16
src/compiler/checker.ts
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@@ -23674,6 +23674,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return isArrayType(type) || !(type.flags & TypeFlags.Nullable) && isTypeAssignableTo(type, anyReadonlyArrayType);
}
function isMutableArrayLikeType(type: Type): boolean {
// A type is mutable-array-like if it is a reference to the global Array type, or if it is not the
// any, undefined or null type and if it is assignable to Array<any>
return isMutableArrayOrTuple(type) || !(type.flags & (TypeFlags.Any | TypeFlags.Nullable)) && isTypeAssignableTo(type, anyArrayType);
}
function getSingleBaseForNonAugmentingSubtype(type: Type) {
if (!(getObjectFlags(type) & ObjectFlags.Reference) || !(getObjectFlags((type as TypeReference).target) & ObjectFlags.ClassOrInterface)) {
return undefined;
@@ -24338,7 +24344,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
callback(getTypeAtPosition(source, i), getTypeAtPosition(target, i));
}
if (targetRestType) {
callback(getRestTypeAtPosition(source, paramCount), targetRestType);
callback(getRestTypeAtPosition(source, paramCount, /*readonly*/ isConstTypeVariable(targetRestType) && !someType(targetRestType, isMutableArrayLikeType)), targetRestType);
}
}
@@ -30541,7 +30547,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return createTupleType(elementTypes, elementFlags);
}
if (forceTuple || inConstContext || inTupleContext) {
return createArrayLiteralType(createTupleType(elementTypes, elementFlags, /*readonly*/ inConstContext));
return createArrayLiteralType(createTupleType(elementTypes, elementFlags, /*readonly*/ inConstContext && !(contextualType && someType(contextualType, isMutableArrayLikeType))));
}
return createArrayLiteralType(createArrayType(
elementTypes.length ?
@@ -33139,7 +33145,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
names.push((arg as SyntheticExpression).tupleNameSource!);
}
}
return createTupleType(types, flags, inConstContext, length(names) === length(types) ? names : undefined);
return createTupleType(types, flags, inConstContext && !someType(restType, isMutableArrayLikeType), length(names) === length(types) ? names : undefined);
}
function checkTypeArguments(signature: Signature, typeArgumentNodes: readonly TypeNode[], reportErrors: boolean, headMessage?: DiagnosticMessage): Type[] | undefined {
@@ -35455,7 +35461,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return undefined;
}
function getRestTypeAtPosition(source: Signature, pos: number): Type {
function getRestTypeAtPosition(source: Signature, pos: number, readonly?: boolean): Type {
const parameterCount = getParameterCount(source);
const minArgumentCount = getMinArgumentCount(source);
const restType = getEffectiveRestType(source);
@@ -35479,7 +35485,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
names.push(name);
}
}
return createTupleType(types, flags, /*readonly*/ false, length(names) === length(types) ? names : undefined);
return createTupleType(types, flags, readonly, length(names) === length(types) ? names : undefined);
}
// Return the number of parameters in a signature. The rest parameter, if present, counts as one