Allow creating a list of lists from an array of arrays

modules/standard/List.chpl

@@ -518,8 +518,16 @@ module List {
     @chpldoc.nodoc
     proc ref _commonInitFromIterable(iterable) lifetime this < iterable {
       this._firstTimeInitializeArrays();
-      for x in iterable do
-        pushBack(x);
+      if isSubtype(this.eltType, list) {
+        for x in iterable {
+          var subList: this.eltType = x;
+          pushBack(subList);
+        }
+      } else {
+        for x in iterable {
+          pushBack(x);
+        }
+      }
     }
 
     @chpldoc.nodoc

test/library/standard/List/initEquals/listInitEqualsArrayBug.chpl

@@ -0,0 +1,9 @@
+use List;
+
+// this works, creates a list of arrays
+var a: list(?) = [[1,2,3],[4,5,6]];
+compilerWarning(a.type:string);
+
+// this segfaults at runtime, no matter the domain used for the array
+var b: list([1..3] int) = [[1,2,3],[4,5,6]];
+compilerWarning(b.type:string);

test/library/standard/List/initEquals/listInitEqualsArrayBug.future

@@ -0,0 +1 @@
+bug: init= segfaults at runtime

test/library/standard/List/initEquals/listInitEqualsArrayBug.good

@@ -0,0 +1,2 @@
+listInitEqualsArrayBug.chpl:5: warning: list([domain(1,int(64),one)] int(64),false)
+listInitEqualsArrayBug.chpl:9: warning: list([domain(1,int(64),one)] int(64),false)

test/library/standard/List/initEquals/listInitEqualsNestedArray.chpl

@@ -0,0 +1,20 @@
+use List;
+
+var lst1: list(list(string)) = [["1", "2", "3"], ["a","b","c"]];
+writeln(lst1.type: string);
+writeln(lst1);
+
+var lst2: list(list(list(string))) = [
+  [["1", "2", "3"], ["a","b","c"]],
+  [["4", "5", "6"], ["d","e","f"]]
+];
+writeln(lst2.type: string);
+writeln(lst2);
+
+var lst3 = new list([1, 3, 5]);
+writeln(lst3.type: string);
+writeln(lst3);
+
+var lst4 = new list([[1,2,3], [4,5,6]]);
+writeln(lst4.type: string);
+writeln(lst4);

test/library/standard/List/initEquals/listInitEqualsNestedArray.good

@@ -0,0 +1,8 @@
+list(list(string,false),false)
+[[1, 2, 3], [a, b, c]]
+list(list(list(string,false),false),false)
+[[[1, 2, 3], [a, b, c]], [[4, 5, 6], [d, e, f]]]
+list(int(64),false)
+[1, 3, 5]
+list([domain(1,int(64),one)] int(64),false)
+[1 2 3, 4 5 6]