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Add checks for remaining truthiness positions

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This commit is contained in:
Ryan Cavanaugh
2018-08-06 16:11:43 -07:00
parent 14d3c69c72
commit ca10b7a6fa
5 changed files with 516 additions and 5 deletions
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18
src/compiler/checker.ts
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@@ -20949,6 +20949,7 @@ namespace ts {
}
return numberType;
case SyntaxKind.ExclamationToken:
checkTruthinessExpression(node.operand);
const facts = getTypeFacts(operandType) & (TypeFacts.Truthy | TypeFacts.Falsy);
return facts === TypeFacts.Truthy ? falseType :
facts === TypeFacts.Falsy ? trueType :
@@ -21316,7 +21317,14 @@ namespace ts {
if (operator === SyntaxKind.EqualsToken && (left.kind === SyntaxKind.ObjectLiteralExpression || left.kind === SyntaxKind.ArrayLiteralExpression)) {
return checkDestructuringAssignment(left, checkExpression(right, checkMode), checkMode);
}
let leftType = checkExpression(left, checkMode);
let leftType: Type;
if (operator === SyntaxKind.AmpersandAmpersandToken || operator === SyntaxKind.BarBarToken) {
leftType = checkTruthinessExpression(left, checkMode);
}
else {
leftType = checkExpression(left, checkMode);
}
let rightType = checkExpression(right, checkMode);
switch (operator) {
case SyntaxKind.AsteriskToken:
@@ -21649,7 +21657,7 @@ namespace ts {
}
function checkConditionalExpression(node: ConditionalExpression, checkMode?: CheckMode): Type {
checkExpression(node.condition);
checkTruthinessExpression(node.condition);
const type1 = checkExpression(node.whenTrue, checkMode);
const type2 = checkExpression(node.whenFalse, checkMode);
return getUnionType([type1, type2], UnionReduction.Subtype);
@@ -24538,9 +24546,9 @@ namespace ts {
checkSourceElement(node.statement);
}
function checkTruthinessExpression(node: Expression) {
const type = checkExpression(node);
if (type === voidType) {
function checkTruthinessExpression(node: Expression, checkMode?: CheckMode) {
const type = checkExpression(node, checkMode);
if (type.flags & TypeFlags.Void) {
error(node, Diagnostics.An_expression_of_type_void_cannot_be_tested_for_truthiness);
}
return type;