Skylark: Validate function arguments.

--
MOS_MIGRATED_REVID=86087783
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
index e24d97f..a5190a6 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
@@ -533,7 +533,9 @@
 
   @Override
   SkylarkType validate(ValidationEnvironment env) throws EvalException {
-    // TODO(bazel-team): implement semantical check.
+    for (Argument arg : args) {
+      arg.getValue().validate(env);
+    }
 
     if (obj != null) {
       // TODO(bazel-team): validate function calls on objects too.