Don't attempt to remove the RHS from a 'const' statement.

------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=174107759
google · Nov 1, 2017 · 307e4db · 307e4db
1 parent f91dcb4
commit 307e4db
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Showing 2 changed files with 12 additions and 1 deletion.
diff --git a/src/com/google/javascript/jscomp/DeadAssignmentsElimination.java b/src/com/google/javascript/jscomp/DeadAssignmentsElimination.java
@@ -210,6 +210,11 @@ private void tryRemoveAssignment(NodeTraversal t, Node n, Node exprRoot,
 
     if (NodeUtil.isAssignmentOp(n) || n.isInc() || n.isDec() || isDeclarationNode) {
 
+      if (parent.isConst()) {
+        // Removing the RHS of a const produces as invalid AST.
+        return;
+      }
+
       Node lhs = isDeclarationNode ? n : n.getFirstChild();
       Node rhs = NodeUtil.getRValueOfLValue(lhs);
 

diff --git a/test/com/google/javascript/jscomp/DeadAssignmentsEliminationTest.java b/test/com/google/javascript/jscomp/DeadAssignmentsEliminationTest.java
@@ -706,10 +706,16 @@ public void testLet() {
         "let a; let b; foo(); b = 2; return b;");
   }
 
-  public void testConst() {
+  public void testConst1() {
     inFunction("const a = 1;");
   }
 
+  public void testConst2() {
+    test(
+        "async function f(d) { if (d) { d = 5; } const a = 1; const b = 2; const [x, y] = b; }",
+        "async function f(d) { if (d) {     5; } const a = 1; const b = 2; const [x, y] = b; }");
+  }
+
   public void testBlockScoping() {
     inFunction(
         LINE_JOINER.join(