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Detect always truthy and always falsy types with &&, ||, ! operators

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This commit is contained in:
Anders Hejlsberg 2016-07-02 09:37:50 -07:00
parent a91a293430
commit 881d5105cd
1 changed files with 14 additions and 3 deletions
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17
src/compiler/checker.ts
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@ -201,6 +201,7 @@ namespace ts {
const numericLiteralTypes: Map<LiteralType> = {};
const emptyStringType = getLiteralTypeForText(TypeFlags.StringLiteral, "");
const zeroType = getLiteralTypeForText(TypeFlags.NumberLiteral, "0");
const trueFalseType = getUnionType([trueType, falseType]);
const resolutionTargets: TypeSystemEntity[] = [];
const resolutionResults: boolean[] = [];
@ -6889,6 +6890,10 @@ namespace ts {
type;
}
function isUnionWithTrueOrFalse(type: Type) {
return type.flags & TypeFlags.Union && (contains((<UnionType>type).types, trueType) || contains((<UnionType>type).types, falseType));
}
/**
* Check if a Type was written as a tuple type literal.
* Prefer using isTupleLikeType() unless the use of `elementTypes` is required.
@ -12330,7 +12335,11 @@ namespace ts {
}
return numberType;
case SyntaxKind.ExclamationToken:
return booleanType;
const facts = getTypeFacts(operandType) & (TypeFacts.Truthy | TypeFacts.Falsy);
return facts === TypeFacts.Truthy ? falseType :
facts === TypeFacts.Falsy ? trueType :
isUnionWithTrueOrFalse(operandType) ? trueFalseType :
booleanType;
case SyntaxKind.PlusPlusToken:
case SyntaxKind.MinusMinusToken:
const ok = checkArithmeticOperandType(node.operand, getNonNullableType(operandType),
@ -12713,9 +12722,11 @@ namespace ts {
case SyntaxKind.InKeyword:
return checkInExpression(left, right, leftType, rightType);
case SyntaxKind.AmpersandAmpersandToken:
return strictNullChecks ? includeFalsyTypes(rightType, getFalsyFlags(leftType)) : rightType;
return !strictNullChecks ? rightType :
getTypeFacts(leftType) & TypeFacts.Truthy ? includeFalsyTypes(rightType, getFalsyFlags(leftType)) : leftType;
case SyntaxKind.BarBarToken:
return getUnionType([strictNullChecks ? removeDefinitelyFalsyTypes(leftType) : leftType, rightType]);
return !strictNullChecks ? getUnionType([leftType, rightType]) :
getTypeFacts(leftType) & TypeFacts.Truthy ? getUnionType([removeDefinitelyFalsyTypes(leftType), rightType]) : rightType;
case SyntaxKind.EqualsToken:
checkAssignmentOperator(rightType);
return getRegularTypeOfObjectLiteral(rightType);