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Fix erroneous optional chain narrowing (#36145)

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* Not all optional chains are narrowable references

* Add regression test
This commit is contained in:
Anders Hejlsberg
2020-01-16 16:49:51 -08:00
committed by GitHub
parent b2a7d42032
commit 8517df6fa2
6 changed files with 128 additions and 8 deletions
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17
src/compiler/binder.ts
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@@ -861,7 +861,7 @@ namespace ts {
case SyntaxKind.ThisKeyword:
case SyntaxKind.PropertyAccessExpression:
case SyntaxKind.ElementAccessExpression:
return isNarrowableReference(expr);
return containsNarrowableReference(expr);
case SyntaxKind.CallExpression:
return hasNarrowableArgument(<CallExpression>expr);
case SyntaxKind.ParenthesizedExpression:
@@ -879,20 +879,23 @@ namespace ts {
function isNarrowableReference(expr: Expression): boolean {
return expr.kind === SyntaxKind.Identifier || expr.kind === SyntaxKind.ThisKeyword || expr.kind === SyntaxKind.SuperKeyword ||
(isPropertyAccessExpression(expr) || isNonNullExpression(expr) || isParenthesizedExpression(expr)) && isNarrowableReference(expr.expression) ||
isElementAccessExpression(expr) && isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression) ||
isOptionalChain(expr);
isElementAccessExpression(expr) && isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression);
}
function containsNarrowableReference(expr: Expression): boolean {
return isNarrowableReference(expr) || isOptionalChain(expr) && containsNarrowableReference(expr.expression);
}
function hasNarrowableArgument(expr: CallExpression) {
if (expr.arguments) {
for (const argument of expr.arguments) {
if (isNarrowableReference(argument)) {
if (containsNarrowableReference(argument)) {
return true;
}
}
}
if (expr.expression.kind === SyntaxKind.PropertyAccessExpression &&
isNarrowableReference((<PropertyAccessExpression>expr.expression).expression)) {
containsNarrowableReference((<PropertyAccessExpression>expr.expression).expression)) {
return true;
}
return false;
@@ -909,7 +912,7 @@ namespace ts {
function isNarrowingBinaryExpression(expr: BinaryExpression) {
switch (expr.operatorToken.kind) {
case SyntaxKind.EqualsToken:
return isNarrowableReference(expr.left);
return containsNarrowableReference(expr.left);
case SyntaxKind.EqualsEqualsToken:
case SyntaxKind.ExclamationEqualsToken:
case SyntaxKind.EqualsEqualsEqualsToken:
@@ -938,7 +941,7 @@ namespace ts {
return isNarrowableOperand((<BinaryExpression>expr).right);
}
}
return isNarrowableReference(expr);
return containsNarrowableReference(expr);
}
function createBranchLabel(): FlowLabel {