Fix continue in loops sometimes generating dead code (#1640)

Perryvw · web-flow · commit 9a9817e2c89d · 2025-06-08T16:23:14.000+02:00
diff --git a/src/transformation/visitors/loops/utils.ts b/src/transformation/visitors/loops/utils.ts
@@ -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()])
diff --git a/test/unit/loops.spec.ts b/test/unit/loops.spec.ts
@@ -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;
