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Suport both x != null and x != undefined in non-null type guards

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This commit is contained in:
Anders Hejlsberg 2016-02-19 16:48:58 -08:00
parent d10017f165
commit ed40fbf2d8
1 changed files with 6 additions and 1 deletions
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7
src/compiler/checker.ts
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@ -6986,6 +6986,11 @@ namespace ts {
}
}
function isNullOrUndefinedLiteral(node: Expression) {
return node.kind === SyntaxKind.NullKeyword ||
node.kind === SyntaxKind.Identifier && getResolvedSymbol(<Identifier>node) === undefinedSymbol;
}
// Get the narrowed type of a given symbol at a given location
function getNarrowedTypeOfSymbol(symbol: Symbol, node: Node) {
let type = getTypeOfSymbol(symbol);
@ -7069,7 +7074,7 @@ namespace ts {
switch (expr.operatorToken.kind) {
case SyntaxKind.EqualsEqualsToken:
case SyntaxKind.ExclamationEqualsToken:
if (expr.right.kind === SyntaxKind.NullKeyword) {
if (isNullOrUndefinedLiteral(expr.right)) {
return narrowTypeByNullCheck(type, expr, assumeTrue);
}
// Fall through