1 files changed, 30 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/LValue.java b/src/main/java/com/google/devtools/build/lib/syntax/LValue.java
index 22d686bf4e..ecc72073fe 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/LValue.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/LValue.java
@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.lib.syntax;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.util.Preconditions;
 import java.io.Serializable;
@@ -73,6 +74,35 @@ public class LValue implements Serializable {
     }
   }
 
+  /**
+   *  Returns all names bound by this LValue.
+   *
+   *  Examples:
+   *  <ul>
+   *  <li><{@code x = ...} binds x.</li>
+   *  <li><{@code x, [y,z] = ..} binds x, y, z.</li>
+   *  <li><{@code x[5] = ..} does not bind any names.</li>
+   *  </ul>
+   */
+  public ImmutableSet<String> boundNames() {
+    ImmutableSet.Builder<String> result = ImmutableSet.builder();
+    collectBoundNames(expr, result);
+    return result.build();
+  }
+
+  private static void collectBoundNames(Expression lhs, ImmutableSet.Builder<String> result) {
+    if (lhs instanceof Identifier) {
+      result.add(((Identifier) lhs).getName());
+      return;
+    }
+    if (lhs instanceof ListLiteral) {
+      ListLiteral variables = (ListLiteral) lhs;
+      for (Expression expression : variables.getElements()) {
+        collectBoundNames(expression, result);
+      }
+    }
+  }
+
   private static void doAssign(
       Environment env, Location loc, Expression lhs, Object result)
       throws EvalException, InterruptedException {