1 files changed, 4 insertions, 10 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 1f031d9cc2..729dd0c160 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
@@ -16,7 +16,6 @@ package com.google.devtools.build.lib.syntax;
 
 import static com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils.append;
 
-import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
 import com.google.devtools.build.lib.syntax.compiler.DebugInfo.AstAccessors;
@@ -32,9 +31,7 @@ import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 
 /**
  * Class representing an LValue.
@@ -106,23 +103,20 @@ public class LValue implements Serializable {
 
   // Since dict is still immutable, the expression 'a[x] = b' creates a new dictionary and
   // assigns it to 'a'.
-  // TODO(bazel-team): make dict mutable - this function should be O(1) instead of O(n).
+  @SuppressWarnings("unchecked")
   private static void assignItem(
       Environment env, Location loc, Identifier ident, Object key, Object value)
       throws EvalException, InterruptedException {
     Object o = ident.eval(env);
-    if (!(o instanceof Map)) {
+    if (!(o instanceof SkylarkDict)) {
       throw new EvalException(
           loc,
           "can only assign an element in a dictionary, not in a '"
               + EvalUtils.getDataTypeName(o)
               + "'");
     }
-    Map<?, ?> dict = (Map<?, ?>) o;
-    Map<Object, Object> result = new LinkedHashMap<>(dict.size() + 1);
-    result.putAll(dict);
-    result.put(key, value);
-    env.update(ident.getName(), ImmutableMap.copyOf(result));
+    SkylarkDict<Object, Object> dict = (SkylarkDict<Object, Object>) o;
+    dict.put(key, value, loc, env);
   }
 
   /**