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Change typeof narrowing to narrow selected union members (#25243)

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* For typeof narrow all union members prior to filtering

* Revise narrowTypeByTypeof to both narrow unions and applicable union members

* Add repros from issue
This commit is contained in:
Wesley Wigham
2018-09-06 00:41:09 -07:00
committed by GitHub
parent c62920ac81
commit d8f736d319
9 changed files with 218 additions and 48 deletions
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46
src/compiler/checker.ts
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@@ -14963,30 +14963,34 @@ namespace ts {
if (type.flags & TypeFlags.Any && literal.text === "function") {
return type;
}
if (assumeTrue && !(type.flags & TypeFlags.Union)) {
if (type.flags & TypeFlags.Unknown && literal.text === "object") {
return getUnionType([nonPrimitiveType, nullType]);
}
// We narrow a non-union type to an exact primitive type if the non-union type
// is a supertype of that primitive type. For example, type 'any' can be narrowed
// to one of the primitive types.
const targetType = literal.text === "function" ? globalFunctionType : typeofTypesByName.get(literal.text);
if (targetType) {
if (isTypeSubtypeOf(targetType, type)) {
return targetType;
}
if (type.flags & TypeFlags.Instantiable) {
const constraint = getBaseConstraintOfType(type) || anyType;
if (isTypeSubtypeOf(targetType, constraint)) {
return getIntersectionType([type, targetType]);
}
}
}
}
const facts = assumeTrue ?
typeofEQFacts.get(literal.text) || TypeFacts.TypeofEQHostObject :
typeofNEFacts.get(literal.text) || TypeFacts.TypeofNEHostObject;
return getTypeWithFacts(type, facts);
return getTypeWithFacts(assumeTrue ? mapType(type, narrowTypeForTypeof) : type, facts);
function narrowTypeForTypeof(type: Type) {
if (assumeTrue && !(type.flags & TypeFlags.Union)) {
if (type.flags & TypeFlags.Unknown && literal.text === "object") {
return getUnionType([nonPrimitiveType, nullType]);
}
// We narrow a non-union type to an exact primitive type if the non-union type
// is a supertype of that primitive type. For example, type 'any' can be narrowed
// to one of the primitive types.
const targetType = literal.text === "function" ? globalFunctionType : typeofTypesByName.get(literal.text);
if (targetType) {
if (isTypeSubtypeOf(targetType, type)) {
return isTypeAny(type) ? targetType : getIntersectionType([type, targetType]); // Intersection to handle `string` being a subtype of `keyof T`
}
if (type.flags & TypeFlags.Instantiable) {
const constraint = getBaseConstraintOfType(type) || anyType;
if (isTypeSubtypeOf(targetType, constraint)) {
return getIntersectionType([type, targetType]);
}
}
}
}
return type;
}
}
function narrowTypeBySwitchOnDiscriminant(type: Type, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number) {