Rewrite let and const in MoveFunctionDeclarations (followup CL will rename the pass) to enable wrapping top level code in try/catch blocks.

PiperOrigin-RevId: 323053574

Author: concavelenz

src/com/google/javascript/jscomp/MoveFunctionDeclarations.java

@@ -23,6 +23,7 @@
 import com.google.javascript.jscomp.NodeTraversal.Callback;
 import com.google.javascript.rhino.IR;
 import com.google.javascript.rhino.Node;
+import com.google.javascript.rhino.Token;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map.Entry;
@@ -118,5 +119,10 @@ public void visit(NodeTraversal t, Node n, Node parent) {
     if (NodeUtil.isClassDeclaration(n)) {
       classes.add(n);
     }
+
+    if (n.isConst() || n.isLet()) {
+      n.setToken(Token.VAR);
+      compiler.reportChangeToEnclosingScope(n);
+    }
   }
 }

test/com/google/javascript/jscomp/MoveFunctionDeclarationsTest.java

@@ -86,4 +86,18 @@ public void testNoMoveDeepFunctionDeclarations() {
     testSame("a; if (a) function f(){};");
     testSame("a; if (a) { function f(){} }");
   }
+
+  @Test
+  public void testMigrateLetConstToVar1() {
+    setAcceptedLanguage(CompilerOptions.LanguageMode.ECMASCRIPT_2015);
+    test("let a = 1;", "var a = 1");
+    test("const a = 2;", "var a = 2");
+  }
+
+  @Test
+  public void testMigrateLetConstToVar2() {
+    setAcceptedLanguage(CompilerOptions.LanguageMode.ECMASCRIPT_2015);
+    testSame("{let a = 1;}");
+    testSame("{const a = 2;}");
+  }
 }