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Limit the narrow-to-fresh rule added with boolean literals to only boolean literals (#27274) (#27319)

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* Remove the narrow-to-fresh rule added with boolean literals

* Revert "Remove the narrow-to-fresh rule added with boolean literals"

This reverts commit 9f96fe5da3.

* Only apply freshness to booleans for now

* Add largeish example from issue

* Should be AND not OR

* Add minor improvements suggested by @ahejelsberg

* Reorder conditional a bit
This commit is contained in:
Wesley Wigham
2018-09-24 13:51:00 -07:00
committed by GitHub
parent d715d835c6
commit dd9d5d1398
6 changed files with 576 additions and 4 deletions
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8
src/compiler/checker.ts
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@@ -8868,7 +8868,7 @@ namespace ts {
}
switch (unionReduction) {
case UnionReduction.Literal:
if (includes & TypeFlags.StringOrNumberLiteralOrUnique) {
if (includes & TypeFlags.StringOrNumberLiteralOrUnique | TypeFlags.BooleanLiteral) {
removeRedundantLiteralTypes(typeSet, includes);
}
break;
@@ -12933,8 +12933,8 @@ namespace ts {
function getDefinitelyFalsyPartOfType(type: Type): Type {
return type.flags & TypeFlags.String ? emptyStringType :
type.flags & TypeFlags.Number ? zeroType :
type.flags & TypeFlags.Boolean || type === regularFalseType ? regularFalseType :
type === falseType ? falseType :
type === regularFalseType ||
type === falseType ||
type.flags & (TypeFlags.Void | TypeFlags.Undefined | TypeFlags.Null) ||
type.flags & TypeFlags.StringLiteral && (<LiteralType>type).value === "" ||
type.flags & TypeFlags.NumberLiteral && (<LiteralType>type).value === 0 ? type :
@@ -14200,7 +14200,7 @@ namespace ts {
return assignedType;
}
let reducedType = filterType(declaredType, t => typeMaybeAssignableTo(assignedType, t));
if (assignedType.flags & (TypeFlags.FreshLiteral | TypeFlags.Literal)) {
if (assignedType.flags & TypeFlags.FreshLiteral && assignedType.flags & TypeFlags.BooleanLiteral) {
reducedType = mapType(reducedType, getFreshTypeOfLiteralType); // Ensure that if the assignment is a fresh type, that we narrow to fresh types
}
// Our crude heuristic produces an invalid result in some cases: see GH#26130.