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Don't substitue if the source & target's base types aren't the same.

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Daniel Rosenwasser 2017-05-12 01:17:06 -07:00
parent ee931a8fc8
commit 266bc47e50
1 changed files with 20 additions and 10 deletions
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30
src/compiler/checker.ts
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@ -8577,19 +8577,29 @@ namespace ts {
// and noise for experienced users. Here we can do an extra check in the error case to
// see whether or not substituting in the base types could simplify what we display to the user.
replaceLiterals: {
let sourceReplacement;
let targetReplacement;
if (isTypeOfKind(source, TypeFlags.Literal)) {
const baseSource = getBaseTypeOfLiteralType(source);
if (isTypeRelatedTo(baseSource, target, relation)) {
break replaceLiterals;
}
source = baseSource;
sourceReplacement = getBaseTypeOfLiteralType(source);
}
if (isTypeOfKind(target, TypeFlags.Literal)) {
const baseTarget = getBaseTypeOfLiteralType(target);
if (isTypeRelatedTo(source, baseTarget, relation)) {
break replaceLiterals;
}
target = baseTarget;
targetReplacement = getBaseTypeOfLiteralType(target);
}
// If they both have the same base type, it's probably useful to report the literal type.
if (sourceReplacement === targetReplacement) {
break replaceLiterals;
}
// We substitute the source with the base type *only* if
// the relation with the target remains the same.
if (sourceReplacement && !isTypeRelatedTo(sourceReplacement, target, relation)) {
source = sourceReplacement;
}
// Likewise, only substitue the target if the relation with the source
// (or potentially the base-type of the source!) remains the same.
if (targetReplacement && !isTypeRelatedTo(source, targetReplacement, relation)) {
target = targetReplacement;
}
}