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Allow nested assignments in type guards

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This commit is contained in:
Anders Hejlsberg 2016-06-07 17:37:03 -07:00
parent 5fef0804c8
commit 6a243e3d1d
1 changed files with 22 additions and 6 deletions
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28
src/compiler/checker.ts
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@ -7662,6 +7662,21 @@ namespace ts {
getInitialTypeOfBindingElement(<BindingElement>node);
}
function getReferenceFromExpression(node: Expression): Expression {
switch (node.kind) {
case SyntaxKind.ParenthesizedExpression:
return getReferenceFromExpression((<ParenthesizedExpression>node).expression);
case SyntaxKind.BinaryExpression:
switch ((<BinaryExpression>node).operatorToken.kind) {
case SyntaxKind.EqualsToken:
return getReferenceFromExpression((<BinaryExpression>node).left);
case SyntaxKind.CommaToken:
return getReferenceFromExpression((<BinaryExpression>node).right);
}
}
return node;
}
function getFlowTypeOfReference(reference: Node, declaredType: Type, assumeInitialized: boolean, includeOuterFunctions: boolean) {
let key: string;
if (!reference.flowNode || assumeInitialized && !(declaredType.flags & TypeFlags.Narrowable)) {
@ -7882,7 +7897,7 @@ namespace ts {
if (operator === SyntaxKind.ExclamationEqualsToken || operator === SyntaxKind.ExclamationEqualsEqualsToken) {
assumeTrue = !assumeTrue;
}
if (!strictNullChecks || !isMatchingReference(reference, expr.left)) {
if (!strictNullChecks || !isMatchingReference(reference, getReferenceFromExpression(expr.left))) {
return type;
}
const doubleEquals = operator === SyntaxKind.EqualsEqualsToken || operator === SyntaxKind.ExclamationEqualsToken;
@ -7897,12 +7912,12 @@ namespace ts {
function narrowTypeByTypeof(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
// We have '==', '!=', '====', or !==' operator with 'typeof xxx' on the left
// and string literal on the right
const left = <TypeOfExpression>expr.left;
const left = getReferenceFromExpression((<TypeOfExpression>expr.left).expression);
const right = <LiteralExpression>expr.right;
if (!isMatchingReference(reference, left.expression)) {
if (!isMatchingReference(reference, left)) {
// For a reference of the form 'x.y', a 'typeof x === ...' type guard resets the
// narrowed type of 'y' to its declared type.
if (containsMatchingReference(reference, left.expression)) {
if (containsMatchingReference(reference, left)) {
return declaredType;
}
return type;
@ -7927,10 +7942,11 @@ namespace ts {
}
function narrowTypeByInstanceof(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
if (!isMatchingReference(reference, expr.left)) {
const left = getReferenceFromExpression(expr.left);
if (!isMatchingReference(reference, left)) {
// For a reference of the form 'x.y', an 'x instanceof T' type guard resets the
// narrowed type of 'y' to its declared type.
if (containsMatchingReference(reference, expr.left)) {
if (containsMatchingReference(reference, left)) {
return declaredType;
}
return type;