Optimize LValue#boundIdentifiers for common case

I'm assuming most of the time folks are only assigning one variable, which
doesn't require an ImmutableSet.Builder and the garbage it comes with.

Also took the liberty of removing some unused InterruptedException
declarations.

PiperOrigin-RevId: 187068400

1 files changed, 10 insertions, 5 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 2b539a93fe..4cc38f4968 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
@@ -92,7 +92,7 @@ public final class LValue extends ASTNode {
    */
   private static void assignIdentifier(
       Identifier ident, Object value, Environment env, Location loc)
-      throws EvalException, InterruptedException {
+      throws EvalException {
     Preconditions.checkNotNull(value, "trying to assign null to %s", ident);
 
     if (env.isKnownGlobalVariable(ident.getName())) {
@@ -116,7 +116,7 @@ public final class LValue extends ASTNode {
   @SuppressWarnings("unchecked")
   private static void assignItem(
       Object object, Object key, Object value, Environment env, Location loc)
-      throws EvalException, InterruptedException {
+      throws EvalException {
     if (object instanceof SkylarkDict) {
       SkylarkDict<Object, Object> dict = (SkylarkDict<Object, Object>) object;
       dict.put(key, value, loc, env);
@@ -207,9 +207,14 @@ public final class LValue extends ASTNode {
    * </ul>
    */
   public ImmutableSet<Identifier> boundIdentifiers() {
-    ImmutableSet.Builder<Identifier> result = ImmutableSet.builder();
-    collectBoundIdentifiers(expr, result);
-    return result.build();
+    if (expr instanceof Identifier) {
+      // Common case/fast path - skip the builder.
+      return ImmutableSet.of((Identifier) expr);
+    } else {
+      ImmutableSet.Builder<Identifier> result = ImmutableSet.builder();
+      collectBoundIdentifiers(expr, result);
+      return result.build();
+    }
   }
 
   private static void collectBoundIdentifiers(