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Merge pull request #14006 from Microsoft/better-discriminated-union-errors

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Improve discriminated union error messages
This commit is contained in:
Nathan Shively-Sanders
2017-02-13 14:14:22 -08:00
committed by GitHub
parent 58b8a54e5f 271ca80c75
commit ba8330cba6
4 changed files with 79 additions and 3 deletions
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26
src/compiler/checker.ts
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@@ -7783,16 +7783,36 @@ namespace ts {
if (target.flags & TypeFlags.Union && containsType(targetTypes, source)) {
return Ternary.True;
}
const len = targetTypes.length;
for (let i = 0; i < len; i++) {
const related = isRelatedTo(source, targetTypes[i], reportErrors && i === len - 1);
for (const type of targetTypes) {
const related = isRelatedTo(source, type, /*reportErrors*/ false);
if (related) {
return related;
}
}
if (reportErrors) {
const discriminantType = findMatchingDiscriminantType(source, target);
isRelatedTo(source, discriminantType || targetTypes[targetTypes.length - 1], /*reportErrors*/ true);
}
return Ternary.False;
}
function findMatchingDiscriminantType(source: Type, target: UnionOrIntersectionType) {
const sourceProperties = getPropertiesOfObjectType(source);
if (sourceProperties) {
for (const sourceProperty of sourceProperties) {
if (isDiscriminantProperty(target, sourceProperty.name)) {
const sourceType = getTypeOfSymbol(sourceProperty);
for (const type of target.types) {
const targetType = getTypeOfPropertyOfType(type, sourceProperty.name);
if (targetType && isRelatedTo(sourceType, targetType)) {
return type;
}
}
}
}
}
}
function typeRelatedToEachType(source: Type, target: UnionOrIntersectionType, reportErrors: boolean): Ternary {
let result = Ternary.True;
const targetTypes = target.types;