Fix captured let/const in 'for' condition or incrementer (#47681)

Author: rbuckton

src/compiler/transformers/es2015.ts

@@ -2954,9 +2954,11 @@ namespace ts {
             // variables declared in the loop initializer that will be changed inside the loop
             const loopOutParameters: LoopOutParameter[] = [];
             if (loopInitializer && (getCombinedNodeFlags(loopInitializer) & NodeFlags.BlockScoped)) {
-                const hasCapturedBindingsInForInitializer = shouldConvertInitializerOfForStatement(node);
+                const hasCapturedBindingsInForHead = shouldConvertInitializerOfForStatement(node) ||
+                    shouldConvertConditionOfForStatement(node) ||
+                    shouldConvertIncrementorOfForStatement(node);
                 for (const decl of loopInitializer.declarations) {
-                    processLoopVariableDeclaration(node, decl, loopParameters, loopOutParameters, hasCapturedBindingsInForInitializer);
+                    processLoopVariableDeclaration(node, decl, loopParameters, loopOutParameters, hasCapturedBindingsInForHead);
                 }
             }
 
@@ -3434,26 +3436,32 @@ namespace ts {
             });
         }
 
-        function processLoopVariableDeclaration(container: IterationStatement, decl: VariableDeclaration | BindingElement, loopParameters: ParameterDeclaration[], loopOutParameters: LoopOutParameter[], hasCapturedBindingsInForInitializer: boolean) {
+        function processLoopVariableDeclaration(container: IterationStatement, decl: VariableDeclaration | BindingElement, loopParameters: ParameterDeclaration[], loopOutParameters: LoopOutParameter[], hasCapturedBindingsInForHead: boolean) {
             const name = decl.name;
             if (isBindingPattern(name)) {
                 for (const element of name.elements) {
                     if (!isOmittedExpression(element)) {
-                        processLoopVariableDeclaration(container, element, loopParameters, loopOutParameters, hasCapturedBindingsInForInitializer);
+                        processLoopVariableDeclaration(container, element, loopParameters, loopOutParameters, hasCapturedBindingsInForHead);
                     }
                 }
             }
             else {
                 loopParameters.push(factory.createParameterDeclaration(/*decorators*/ undefined, /*modifiers*/ undefined, /*dotDotDotToken*/ undefined, name));
                 const checkFlags = resolver.getNodeCheckFlags(decl);
-                if (checkFlags & NodeCheckFlags.NeedsLoopOutParameter || hasCapturedBindingsInForInitializer) {
+                if (checkFlags & NodeCheckFlags.NeedsLoopOutParameter || hasCapturedBindingsInForHead) {
                     const outParamName = factory.createUniqueName("out_" + idText(name));
                     let flags: LoopOutParameterFlags = 0;
                     if (checkFlags & NodeCheckFlags.NeedsLoopOutParameter) {
                         flags |= LoopOutParameterFlags.Body;
                     }
-                    if (isForStatement(container) && container.initializer && resolver.isBindingCapturedByNode(container.initializer, decl)) {
-                        flags |= LoopOutParameterFlags.Initializer;
+                    if (isForStatement(container)) {
+                        if (container.initializer && resolver.isBindingCapturedByNode(container.initializer, decl)) {
+                            flags |= LoopOutParameterFlags.Initializer;
+                        }
+                        if (container.condition && resolver.isBindingCapturedByNode(container.condition, decl) ||
+                            container.incrementor && resolver.isBindingCapturedByNode(container.incrementor, decl)) {
+                            flags |= LoopOutParameterFlags.Body;
+                        }
                     }
                     loopOutParameters.push({ flags, originalName: name, outParamName });
                 }

tests/baselines/reference/capturedLetConstInLoop1.js

@@ -231,11 +231,13 @@ var _loop_11 = function (y) {
     else
         inc_1 = true;
     if (!(use(function () { return y; }), y < 1))
-        return "break";
+        return out_y_2 = y, "break";
+    out_y_2 = y;
 };
-var inc_1 = false;
+var out_y_2, inc_1 = false;
 for (var y = 0;;) {
     var state_1 = _loop_11(y);
+    y = out_y_2;
     if (state_1 === "break")
         break;
 }
@@ -244,28 +246,32 @@ var _loop_12 = function (y) {
         use(function () { return y; }), ++y;
     else
         inc_2 = true;
+    out_y_3 = y;
 };
-var inc_2 = false;
+var out_y_3, inc_2 = false;
 for (var y = 0; y < 1;) {
     _loop_12(y);
+    y = out_y_3;
 }
 var _loop_init_2 = function () {
     var y = (use(function () { return y; }), 0);
-    out_y_2 = y;
+    out_y_4 = y;
 };
 var _loop_13 = function (y) {
     if (inc_3)
         use(function () { return y; }), ++y;
     else
         inc_3 = true;
     if (!(use(function () { return y; }), y < 1))
-        return out_y_2 = y, "break";
+        return out_y_4 = y, "break";
     use(function () { return y; });
+    out_y_4 = y;
 };
-var out_y_2, inc_3 = false;
+var out_y_4, inc_3 = false;
 _loop_init_2();
-for (var y = out_y_2;;) {
+for (var y = out_y_4;;) {
     var state_2 = _loop_13(y);
+    y = out_y_4;
     if (state_2 === "break")
         break;
 }