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Merged
Perryvw merged 2 commits into from
Nov 21, 2021
Merged

Nullish coalescing with preceding statements #1172

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bd87d2e
Nullish coalescing with preceding statements
GlassBricks Nov 20, 2021
2652226
Add test for #1165
GlassBricks Nov 20, 2021
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46 changes: 13 additions & 33 deletions src/transformation/visitors/binary-expression/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@ function transformBinaryOperationWithNoPrecedingStatements(

if (operator === ts.SyntaxKind.QuestionQuestionToken) {
assert(ts.isBinaryExpression(node));
return transformNullishCoalescingExpression(context, node, left, right);
return transformNullishCoalescingOperationNoPrecedingStatements(context, node, left, right);
}

let luaOperator = simpleOperatorsToLua[operator];
Expand Down Expand Up @@ -138,21 +138,7 @@ function transformShortCircuitBinaryExpression(
const [rightPrecedingStatements, rhs] = transformInPrecedingStatementScope(context, () =>
context.transformExpression(node.right)
);
if (rightPrecedingStatements.length > 0) {
return createShortCircuitBinaryExpressionPrecedingStatements(
context,
lhs,
rhs,
rightPrecedingStatements,
operator,
node
);
} else {
return [
rightPrecedingStatements,
transformBinaryOperationWithNoPrecedingStatements(context, lhs, rhs, operator, node),
];
}
return transformBinaryOperation(context, lhs, rhs, rightPrecedingStatements, operator, node);
}

export function transformBinaryOperation(
Expand Down Expand Up @@ -274,7 +260,7 @@ export function transformBinaryExpressionStatement(
}
}

function transformNullishCoalescingExpression(
function transformNullishCoalescingOperationNoPrecedingStatements(
context: TransformationContext,
node: ts.BinaryExpression,
transformedLeft: lua.Expression,
Expand All @@ -287,23 +273,17 @@ function transformNullishCoalescingExpression(
(type.flags & (ts.TypeFlags.Any | ts.TypeFlags.Unknown | ts.TypeFlags.Boolean)) !== 0 ||
(type.flags & ts.TypeFlags.BooleanLiteral & ts.TypeFlags.PossiblyFalsy) !== 0;
if (typeCanSatisfy(context, lhsType, typeCanBeFalse)) {
// lhs can be false, transform to IIFE
const lhsIdentifier = lua.createIdentifier("____lhs");
const nilComparison = lua.createBinaryExpression(
lua.cloneIdentifier(lhsIdentifier),
lua.createNilLiteral(),
lua.SyntaxKind.EqualityOperator
);
// if ____ == nil then return rhs else return ____ end
const ifStatement = lua.createIfStatement(
nilComparison,
lua.createBlock([lua.createReturnStatement([transformedRight])]),
lua.createBlock([lua.createReturnStatement([lua.cloneIdentifier(lhsIdentifier)])])
);
// (function(lhs') if lhs' == nil then return rhs else return lhs' end)(lhs)
return lua.createCallExpression(lua.createFunctionExpression(lua.createBlock([ifStatement]), [lhsIdentifier]), [
// reuse logic from case with preceding statements
const [precedingStatements, result] = createShortCircuitBinaryExpressionPrecedingStatements(
context,
transformedLeft,
]);
transformedRight,
[],
ts.SyntaxKind.QuestionQuestionToken,
node
);
context.addPrecedingStatements(precedingStatements);
return result;
} else {
// lhs or rhs
return lua.createBinaryExpression(transformedLeft, transformedRight, lua.SyntaxKind.OrOperator, node);
Expand Down
14 changes: 14 additions & 0 deletions test/unit/nullishCoalescing.spec.ts
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Expand Up @@ -40,3 +40,17 @@ test("nullish-coalescing operator with side effect rhs", () => {
return [i, undefined ?? incI(), i];
`.expectToMatchJsResult();
});

test("nullish-coalescing operator with vararg", () => {
util.testFunction`

function foo(...args: any[]){
return args
}
function bar(...args: any[]) {
let x: boolean | undefined = false
const y = x ?? foo(...args)
}
return bar(1, 2)
`.expectToMatchJsResult();
});