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Merge pull request #29714 from Microsoft/fixInstanceofTypeofControlFlow

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Fix instanceof and typeof control flow
This commit is contained in:
Anders Hejlsberg
2019-02-04 12:22:52 -08:00
committed by GitHub
parent f86b635122 026225997e
commit b7c5c073f8
6 changed files with 317 additions and 10 deletions
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24
src/compiler/checker.ts
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@@ -15045,9 +15045,8 @@ namespace ts {
return false;
}
function hasNarrowableDeclaredType(expr: Node) {
const type = getDeclaredTypeOfReference(expr);
return !!(type && type.flags & TypeFlags.Union);
function isSyntheticThisPropertyAccess(expr: Node) {
return isAccessExpression(expr) && expr.expression.kind === SyntaxKind.ThisKeyword && !!(expr.expression.flags & NodeFlags.Synthesized);
}
function findDiscriminantProperties(sourceProperties: Symbol[], target: Type): Symbol[] | undefined {
@@ -16107,9 +16106,9 @@ namespace ts {
// We have '==', '!=', '====', or !==' operator with 'typeof xxx' and string literal operands
const target = getReferenceCandidate(typeOfExpr.expression);
if (!isMatchingReference(reference, target)) {
// For a reference of the form 'x.y', where 'x' has a narrowable declared type, a
// 'typeof x === ...' type guard resets the narrowed type of 'y' to its declared type.
if (containsMatchingReference(reference, target) && hasNarrowableDeclaredType(target)) {
// 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, target)) {
return declaredType;
}
return type;
@@ -16264,9 +16263,14 @@ namespace ts {
function narrowTypeByInstanceof(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
const left = getReferenceCandidate(expr.left);
if (!isMatchingReference(reference, left)) {
// For a reference of the form 'x.y', where 'x' has a narrowable declared type, an
// 'x instanceof T' type guard resets the narrowed type of 'y' to its declared type.
if (containsMatchingReference(reference, left) && hasNarrowableDeclaredType(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. We do this because preceding 'x.y'
// references might reference a different 'y' property. However, we make an exception
// for property accesses where x is a synthetic 'this' expression, indicating that we
// were called from isPropertyInitializedInConstructor. Without this exception,
// initializations of 'this' properties that occur before a 'this instanceof XXX'
// check would not be considered.
if (containsMatchingReference(reference, left) && !isSyntheticThisPropertyAccess(reference)) {
return declaredType;
}
return type;
@@ -27221,7 +27225,7 @@ namespace ts {
reference.expression.parent = reference;
reference.parent = constructor;
reference.flowNode = constructor.returnFlowNode;
const flowType = getFlowTypeOfReference(reference, propType, getOptionalType(propType));
const flowType = getFlowTypeOfReference(reference, getOptionalType(propType));
return !(getFalsyFlags(flowType) & TypeFlags.Undefined);
}