microsoft/TypeScript
1
0
Fork 0
mirror of https://github.com/microsoft/TypeScript.git synced 2026-02-14 19:16:17 -06:00
Code Issues Packages Projects Releases 212 Wiki Activity

Add truthy/falsey guards for nullable types

Browse Source
This commit is contained in:
Anders Hejlsberg 2016-02-16 09:51:49 -08:00
parent 586c3ac86f
commit bf89530e36
1 changed files with 6 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
src/compiler/checker.ts
View File

@ -6993,6 +6993,10 @@ namespace ts {
return type;
function narrowTypeByTruthiness(type: Type, expr: Identifier, assumeTrue: boolean): Type {
return strictNullChecks && assumeTrue && getResolvedSymbol(expr) === symbol ? getNonNullableType(type) : type;
}
function narrowTypeByEquality(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
// Check that we have 'typeof <symbol>' on the left and string literal on the right
if (expr.left.kind !== SyntaxKind.TypeOfExpression || expr.right.kind !== SyntaxKind.StringLiteral) {
@ -7195,6 +7199,8 @@ namespace ts {
// will be a subtype or the same type as the argument.
function narrowType(type: Type, expr: Expression, assumeTrue: boolean): Type {
switch (expr.kind) {
case SyntaxKind.Identifier:
return narrowTypeByTruthiness(type, <Identifier>expr, assumeTrue)
case SyntaxKind.CallExpression:
return narrowTypeByTypePredicate(type, <CallExpression>expr, assumeTrue);
case SyntaxKind.ParenthesizedExpression: