Better API for creating immutable Skylark lists.

--
MOS_MIGRATED_REVID=132226460

2 files changed, 11 insertions, 13 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java b/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java
index 0df0aa4336..8706337739 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java
@@ -623,7 +623,7 @@ public class MethodLibrary {
   };
 
   @SkylarkSignature(name = "splitlines", objectType = StringModule.class,
-      returnType = MutableList.class,
+      returnType = SkylarkList.class,
       doc =
       "Splits the string at line boundaries ('\\n', '\\r\\n', '\\r') "
       + "and returns the result as a list.",
@@ -633,7 +633,7 @@ public class MethodLibrary {
               doc = "Whether the line breaks should be included in the resulting list.")})
   private static final BuiltinFunction splitLines = new BuiltinFunction("splitlines") {
     @SuppressWarnings("unused")
-    public MutableList<String> invoke(String self, Boolean keepEnds) throws EvalException {
+    public SkylarkList<String> invoke(String self, Boolean keepEnds) throws EvalException {
       List<String> result = new ArrayList<>();
       Matcher matcher = SPLIT_LINES_PATTERN.matcher(self);
       while (matcher.find()) {
@@ -649,7 +649,7 @@ public class MethodLibrary {
           result.add(line);
         }
       }
-      return new MutableList(result);
+      return SkylarkList.createImmutable(result);
     }
   };
 
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java
index 05cf33b176..de03e0ace5 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java
@@ -210,6 +210,13 @@ public abstract class SkylarkList<E> extends MutableCollection<E> implements Lis
     return castList(getContentsUnsafe(), type, description);
   }
 
+  /**
+   * Creates immutable SkylarkList with given elements.
+   */
+  public static <E> SkylarkList<E> createImmutable(Iterable<? extends E> contents) {
+    return new MutableList<E>(contents, Mutability.IMMUTABLE);
+  }
+
   /** A class for mutable lists. */
   @SkylarkModule(
     name = "list",
@@ -280,15 +287,6 @@ public abstract class SkylarkList<E> extends MutableCollection<E> implements Lis
     }
 
     /**
-     * Creates a MutableList from contents.
-     * @param contents the contents of the list
-     * @return an actually immutable MutableList containing the elements
-     */
-    public MutableList(Iterable<? extends E> contents) {
-      this(contents, Mutability.IMMUTABLE);
-    }
-
-    /**
      * Creates a mutable or immutable MutableList depending on the given {@link Mutability}.
      */
     public MutableList(Mutability mutability) {
@@ -427,7 +425,7 @@ public abstract class SkylarkList<E> extends MutableCollection<E> implements Lis
     /**
      * An empty IMMUTABLE MutableList.
      */
-    public static final MutableList EMPTY = new MutableList(Tuple.EMPTY);
+    public static final MutableList EMPTY = new MutableList(Tuple.EMPTY, Mutability.IMMUTABLE);
   }
 
   /** An immutable tuple, e.g. in (1, 2, 3) */