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Fix continue in loops sometimes generating dead code #1640

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Merged
Perryvw merged 1 commit into from
Jun 8, 2025
Merged

Fix continue in loops sometimes generating dead code #1640

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20 changes: 16 additions & 4 deletions src/transformation/visitors/loops/utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -31,13 +31,25 @@ export function transformLoopBody(
const identifier = lua.createIdentifier(`__continue${scopeId}`);
const literalTrue = lua.createBooleanLiteral(true);

// If there is a break in the body statements, do not include any code afterwards
const transformedBodyStatements = [];
let bodyBroken = false;
for (const statement of body) {
transformedBodyStatements.push(statement);
if (lua.isBreakStatement(statement)) {
bodyBroken = true;
break;
}
}
if (!bodyBroken) {
// Tell loop to continue if not broken
transformedBodyStatements.push(lua.createAssignmentStatement(identifier, literalTrue));
}

return [
lua.createDoStatement([
lua.createVariableDeclarationStatement(identifier),
lua.createRepeatStatement(
lua.createBlock([...body, lua.createAssignmentStatement(identifier, literalTrue)]),
literalTrue
),
lua.createRepeatStatement(lua.createBlock(transformedBodyStatements), literalTrue),
lua.createIfStatement(
lua.createUnaryExpression(identifier, lua.SyntaxKind.NotOperator),
lua.createBlock([lua.createBreakStatement()])
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14 changes: 14 additions & 0 deletions test/unit/loops.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -560,6 +560,20 @@ for (const testCase of [
});
}

// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1638
test.each([tstl.LuaTarget.Universal, tstl.LuaTarget.Lua50, tstl.LuaTarget.Lua51])(
"no unreachable code when using continue for target %s (#1638)",
target => {
util.testFunction`
let i = 0;
while(++i < 10) continue;
return i;
`
.setOptions({ luaTarget: target })
.expectToMatchJsResult();
}
);

test("do...while", () => {
util.testFunction`
let result = 0;
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