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Improve type relationship error reporting for nullable types

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This commit is contained in:
Anders Hejlsberg 2016-03-05 16:55:54 -08:00
parent 129a4f1908
commit 50d874e09d
1 changed files with 26 additions and 2 deletions
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28
src/compiler/checker.ts
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@ -5701,7 +5701,19 @@ namespace ts {
function typeRelatedToSomeType(source: Type, target: UnionOrIntersectionType, reportErrors: boolean): Ternary {
const targetTypes = target.types;
for (let i = 0, len = targetTypes.length; i < len; i++) {
let len = targetTypes.length;
// The null and undefined types are guaranteed to be at the end of the constituent type list. In order
// to produce the best possible errors we first check the nullable types, such that the last type we
// check and report errors from is a non-nullable type if one is present.
while (len >= 2 && targetTypes[len - 1].flags & TypeFlags.Nullable) {
const related = isRelatedTo(source, targetTypes[len - 1], /*reportErrors*/ false);
if (related) {
return related;
}
len--;
}
// Now check the non-nullable types and report errors on the last one.
for (let i = 0; i < len; i++) {
const related = isRelatedTo(source, targetTypes[i], reportErrors && i === len - 1);
if (related) {
return related;
@ -5725,7 +5737,19 @@ namespace ts {
function someTypeRelatedToType(source: UnionOrIntersectionType, target: Type, reportErrors: boolean): Ternary {
const sourceTypes = source.types;
for (let i = 0, len = sourceTypes.length; i < len; i++) {
let len = sourceTypes.length;
// The null and undefined types are guaranteed to be at the end of the constituent type list. In order
// to produce the best possible errors we first check the nullable types, such that the last type we
// check and report errors from is a non-nullable type if one is present.
while (len >= 2 && sourceTypes[len - 1].flags & TypeFlags.Nullable) {
const related = isRelatedTo(sourceTypes[len - 1], target, /*reportErrors*/ false);
if (related) {
return related;
}
len--;
}
// Now check the non-nullable types and report errors on the last one.
for (let i = 0; i < len; i++) {
const related = isRelatedTo(sourceTypes[i], target, reportErrors && i === len - 1);
if (related) {
return related;