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Compare type parameters, constraints, and defaults in signature identity

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This commit is contained in:
Anders Hejlsberg 2019-06-26 18:09:30 -10:00
parent be4147ddf3
commit ea0a6de82f
1 changed files with 15 additions and 11 deletions
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26
src/compiler/checker.ts
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@ -14322,20 +14322,25 @@ namespace ts {
if (!(isMatchingSignature(source, target, partialMatch))) {
return Ternary.False;
}
// Check that the two signatures have the same number of type parameters. We might consider
// also checking that any type parameter constraints match, but that would require instantiating
// the constraints with a common set of type arguments to get relatable entities in places where
// type parameters occur in the constraints. The complexity of doing that doesn't seem worthwhile,
// particularly as we're comparing erased versions of the signatures below.
// Check that the two signatures have the same number of type parameters.
if (length(source.typeParameters) !== length(target.typeParameters)) {
return Ternary.False;
}
// Spec 1.0 Section 3.8.3 & 3.8.4:
// M and N (the signatures) are instantiated using type Any as the type argument for all type parameters declared by M and N
source = getErasedSignature(source);
target = getErasedSignature(target);
// Check that type parameter constraints and defaults match. If they do, instantiate the source
// signature with the type parameters of the target signature and continue the comparison.
if (target.typeParameters) {
const mapper = createTypeMapper(source.typeParameters!, target.typeParameters);
for (let i = 0; i < target.typeParameters.length; i++) {
const s = source.typeParameters![i];
const t = target.typeParameters[i];
if (!(s === t || compareTypes(instantiateType(getConstraintFromTypeParameter(s), mapper) || unknownType, getConstraintFromTypeParameter(t) || unknownType) &&
compareTypes(instantiateType(getDefaultFromTypeParameter(s), mapper) || unknownType, getDefaultFromTypeParameter(t) || unknownType))) {
return Ternary.False;
}
}
source = instantiateSignature(source, mapper, /*eraseTypeParameters*/ true);
}
let result = Ternary.True;
if (!ignoreThisTypes) {
const sourceThisType = getThisTypeOfSignature(source);
if (sourceThisType) {
@ -14349,7 +14354,6 @@ namespace ts {
}
}
}
const targetLen = getParameterCount(target);
for (let i = 0; i < targetLen; i++) {
const s = getTypeAtPosition(source, i);