Transform setter bodies if they contain es2015 (#22931)

Author: weswigham

src/compiler/transformers/es2015.ts

@@ -1922,7 +1922,7 @@ namespace ts {
             return block;
         }
 
-        function visitFunctionBodyDownLevel(node: FunctionDeclaration | FunctionExpression) {
+        function visitFunctionBodyDownLevel(node: FunctionDeclaration | FunctionExpression | AccessorDeclaration) {
             const updated = visitFunctionBody(node.body, functionBodyVisitor, context);
             return updateBlock(
                 updated,
@@ -3196,18 +3196,15 @@ namespace ts {
             convertedLoopState = undefined;
             const ancestorFacts = enterSubtree(HierarchyFacts.FunctionExcludes, HierarchyFacts.FunctionIncludes);
             let updated: AccessorDeclaration;
-            if (node.transformFlags & TransformFlags.ContainsCapturedLexicalThis) {
-                const parameters = visitParameterList(node.parameters, visitor, context);
-                const body = transformFunctionBody(node);
-                if (node.kind === SyntaxKind.GetAccessor) {
-                    updated = updateGetAccessor(node, node.decorators, node.modifiers, node.name, parameters, node.type, body);
-                }
-                else {
-                    updated = updateSetAccessor(node, node.decorators, node.modifiers, node.name, parameters, body);
-                }
+            const parameters = visitParameterList(node.parameters, visitor, context);
+            const body = node.transformFlags & (TransformFlags.ContainsCapturedLexicalThis | TransformFlags.ContainsES2015)
+                ? transformFunctionBody(node)
+                : visitFunctionBodyDownLevel(node);
+            if (node.kind === SyntaxKind.GetAccessor) {
+                updated = updateGetAccessor(node, node.decorators, node.modifiers, node.name, parameters, node.type, body);
             }
             else {
-                updated = visitEachChild(node, visitor, context);
+                updated = updateSetAccessor(node, node.decorators, node.modifiers, node.name, parameters, body);
             }
             exitSubtree(ancestorFacts, HierarchyFacts.PropagateNewTargetMask, HierarchyFacts.None);
             convertedLoopState = savedConvertedLoopState;

tests/baselines/reference/es5SetterparameterDestructuringNotElided.js

@@ -0,0 +1,16 @@
+//// [es5SetterparameterDestructuringNotElided.ts]
+const foo = {
+    set foo([start, end]: [any, any]) {
+        void start;
+        void end;
+    },
+};
+
+//// [es5SetterparameterDestructuringNotElided.js]
+var foo = {
+    set foo(_a) {
+        var start = _a[0], end = _a[1];
+        void start;
+        void end;
+    },
+};

tests/baselines/reference/es5SetterparameterDestructuringNotElided.symbols

@@ -0,0 +1,17 @@
+=== tests/cases/compiler/es5SetterparameterDestructuringNotElided.ts ===
+const foo = {
+>foo : Symbol(foo, Decl(es5SetterparameterDestructuringNotElided.ts, 0, 5))
+
+    set foo([start, end]: [any, any]) {
+>foo : Symbol(foo, Decl(es5SetterparameterDestructuringNotElided.ts, 0, 13))
+>start : Symbol(start, Decl(es5SetterparameterDestructuringNotElided.ts, 1, 13))
+>end : Symbol(end, Decl(es5SetterparameterDestructuringNotElided.ts, 1, 19))
+
+        void start;
+>start : Symbol(start, Decl(es5SetterparameterDestructuringNotElided.ts, 1, 13))
+
+        void end;
+>end : Symbol(end, Decl(es5SetterparameterDestructuringNotElided.ts, 1, 19))
+
+    },
+};

tests/baselines/reference/es5SetterparameterDestructuringNotElided.types

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/es5SetterparameterDestructuringNotElided.ts ===
+const foo = {
+>foo : { foo: [any, any]; }
+>{    set foo([start, end]: [any, any]) {        void start;        void end;    },} : { foo: [any, any]; }
+
+    set foo([start, end]: [any, any]) {
+>foo : [any, any]
+>start : any
+>end : any
+
+        void start;
+>void start : undefined
+>start : any
+
+        void end;
+>void end : undefined
+>end : any
+
+    },
+};

tests/cases/compiler/es5SetterparameterDestructuringNotElided.ts

@@ -0,0 +1,7 @@
+// @target: es5
+const foo = {
+    set foo([start, end]: [any, any]) {
+        void start;
+        void end;
+    },
+};