Fix class emit in converted loop body (#36795)

src/compiler/transformers/es2015.ts

@@ -2002,10 +2002,16 @@ namespace ts {
             return visitEachChild(node, visitor, context);
         }
 
+        function isVariableStatementOfTypeScriptClassWrapper(node: VariableStatement) {
+            return node.declarationList.declarations.length === 1
+                && !!node.declarationList.declarations[0].initializer
+                && !!(getEmitFlags(node.declarationList.declarations[0].initializer) & EmitFlags.TypeScriptClassWrapper);
+        }
+
         function visitVariableStatement(node: VariableStatement): Statement | undefined {
             const ancestorFacts = enterSubtree(HierarchyFacts.None, hasModifier(node, ModifierFlags.Export) ? HierarchyFacts.ExportedVariableStatement : HierarchyFacts.None);
             let updated: Statement | undefined;
-            if (convertedLoopState && (node.declarationList.flags & NodeFlags.BlockScoped) === 0) {
+            if (convertedLoopState && (node.declarationList.flags & NodeFlags.BlockScoped) === 0 && !isVariableStatementOfTypeScriptClassWrapper(node)) {
                 // we are inside a converted loop - hoist variable declarations
                 let assignments: Expression[] | undefined;
                 for (const decl of node.declarationList.declarations) {
@@ -3606,7 +3612,13 @@ namespace ts {
             // The class statements are the statements generated by visiting the first statement with initializer of the
             // body (1), while all other statements are added to remainingStatements (2)
             const isVariableStatementWithInitializer = (stmt: Statement) => isVariableStatement(stmt) && !!first(stmt.declarationList.declarations).initializer;
+
+            // visit the class body statements outside of any converted loop body.
+            const savedConvertedLoopState = convertedLoopState;
+            convertedLoopState = undefined;
             const bodyStatements = visitNodes(body.statements, visitor, isStatement);
+            convertedLoopState = savedConvertedLoopState;
+
             const classStatements = filter(bodyStatements, isVariableStatementWithInitializer);
             const remainingStatements = filter(bodyStatements, stmt => !isVariableStatementWithInitializer(stmt));
             const varStatement = cast(first(classStatements), isVariableStatement);

tests/baselines/reference/classInConvertedLoopES5.js

@@ -0,0 +1,27 @@
+//// [classInConvertedLoopES5.ts]
+const classesByRow: Record<string, object> = {};
+for (const row of ['1', '2', '3', '4', '5']) {
+  class RowClass {
+    row = row;
+    static factory = () => new RowClass();
+  }
+
+  classesByRow[row] = RowClass;
+}
+
+//// [classInConvertedLoopES5.js]
+var classesByRow = {};
+var _loop_1 = function (row) {
+    var RowClass = /** @class */ (function () {
+        function RowClass() {
+            this.row = row;
+        }
+        RowClass.factory = function () { return new RowClass(); };
+        return RowClass;
+    }());
+    classesByRow[row] = RowClass;
+};
+for (var _i = 0, _a = ['1', '2', '3', '4', '5']; _i < _a.length; _i++) {
+    var row = _a[_i];
+    _loop_1(row);
+}

tests/baselines/reference/classInConvertedLoopES5.symbols

@@ -0,0 +1,25 @@
+=== tests/cases/compiler/classInConvertedLoopES5.ts ===
+const classesByRow: Record<string, object> = {};
+>classesByRow : Symbol(classesByRow, Decl(classInConvertedLoopES5.ts, 0, 5))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+
+for (const row of ['1', '2', '3', '4', '5']) {
+>row : Symbol(row, Decl(classInConvertedLoopES5.ts, 1, 10))
+
+  class RowClass {
+>RowClass : Symbol(RowClass, Decl(classInConvertedLoopES5.ts, 1, 46))
+
+    row = row;
+>row : Symbol(RowClass.row, Decl(classInConvertedLoopES5.ts, 2, 18))
+>row : Symbol(row, Decl(classInConvertedLoopES5.ts, 1, 10))
+
+    static factory = () => new RowClass();
+>factory : Symbol(RowClass.factory, Decl(classInConvertedLoopES5.ts, 3, 14))
+>RowClass : Symbol(RowClass, Decl(classInConvertedLoopES5.ts, 1, 46))
+  }
+
+  classesByRow[row] = RowClass;
+>classesByRow : Symbol(classesByRow, Decl(classInConvertedLoopES5.ts, 0, 5))
+>row : Symbol(row, Decl(classInConvertedLoopES5.ts, 1, 10))
+>RowClass : Symbol(RowClass, Decl(classInConvertedLoopES5.ts, 1, 46))
+}

tests/baselines/reference/classInConvertedLoopES5.types

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/classInConvertedLoopES5.ts ===
+const classesByRow: Record<string, object> = {};
+>classesByRow : Record<string, object>
+>{} : {}
+
+for (const row of ['1', '2', '3', '4', '5']) {
+>row : string
+>['1', '2', '3', '4', '5'] : string[]
+>'1' : "1"
+>'2' : "2"
+>'3' : "3"
+>'4' : "4"
+>'5' : "5"
+
+  class RowClass {
+>RowClass : RowClass
+
+    row = row;
+>row : string
+>row : string
+
+    static factory = () => new RowClass();
+>factory : () => RowClass
+>() => new RowClass() : () => RowClass
+>new RowClass() : RowClass
+>RowClass : typeof RowClass
+  }
+
+  classesByRow[row] = RowClass;
+>classesByRow[row] = RowClass : typeof RowClass
+>classesByRow[row] : object
+>classesByRow : Record<string, object>
+>row : string
+>RowClass : typeof RowClass
+}

tests/cases/compiler/classInConvertedLoopES5.ts

@@ -0,0 +1,10 @@
+// @target: es5
+const classesByRow: Record<string, object> = {};
+for (const row of ['1', '2', '3', '4', '5']) {
+  class RowClass {
+    row = row;
+    static factory = () => new RowClass();
+  }
+
+  classesByRow[row] = RowClass;
+}