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Proper handling of 'null' and 'undefined' in equals and not equals guards

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This commit is contained in:
Anders Hejlsberg
2016-03-05 11:16:31 -08:00
parent 689e28d3ac
commit 8db7af035d
1 changed files with 19 additions and 7 deletions
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src/compiler/checker.ts
+19 -7
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@@ -6388,6 +6388,11 @@ namespace ts {
return flags & TypeFlags.Nullable;
}
function getNullableTypeOfKind(kind: TypeFlags) {
return kind & TypeFlags.Null ? kind & TypeFlags.Undefined ?
getUnionType([nullType, undefinedType]) : nullType : undefinedType;
}
function isNullableType(type: Type) {
return getNullableKind(type) === TypeFlags.Nullable;
}
@@ -7216,12 +7221,11 @@ namespace ts {
switch (expr.operatorToken.kind) {
case SyntaxKind.EqualsEqualsToken:
case SyntaxKind.ExclamationEqualsToken:
case SyntaxKind.EqualsEqualsEqualsToken:
case SyntaxKind.ExclamationEqualsEqualsToken:
if (isNullOrUndefinedLiteral(expr.right)) {
return narrowTypeByNullCheck(type, expr, assumeTrue);
}
// Fall through
case SyntaxKind.EqualsEqualsEqualsToken:
case SyntaxKind.ExclamationEqualsEqualsToken:
if (expr.left.kind === SyntaxKind.TypeOfExpression && expr.right.kind === SyntaxKind.StringLiteral) {
return narrowTypeByTypeof(type, expr, assumeTrue);
}
@@ -7237,14 +7241,22 @@ namespace ts {
}
function narrowTypeByNullCheck(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
// We have '==' or '!=' operator with 'null' or 'undefined' on the right
if (expr.operatorToken.kind === SyntaxKind.ExclamationEqualsToken) {
// We have '==', '!=', '===', or '!==' operator with 'null' or 'undefined' on the right
const operator = expr.operatorToken.kind;
if (operator === SyntaxKind.ExclamationEqualsToken || operator === SyntaxKind.ExclamationEqualsEqualsToken) {
assumeTrue = !assumeTrue;
}
if (!strictNullChecks || assumeTrue || !isMatchingReference(expr.left, reference)) {
if (!strictNullChecks || !isMatchingReference(expr.left, reference)) {
return type;
}
return getNonNullableType(type);
const doubleEquals = operator === SyntaxKind.EqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsToken;
const exprNullableKind = doubleEquals ? TypeFlags.Nullable :
expr.right.kind === SyntaxKind.NullKeyword ? TypeFlags.Null : TypeFlags.Undefined;
if (assumeTrue) {
const nullableKind = getNullableKind(type) & exprNullableKind;
return nullableKind ? getNullableTypeOfKind(nullableKind) : type;
}
return removeNullableKind(type, exprNullableKind);
}
function narrowTypeByTypeof(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {