[AutoDiff] NFC: Add tests for 'AutoDiffIndexSubset' initializers. (#27556)

* Add tests for 'AutoDiffIndexSubset' initializers.
* Unify file headers with #27555.

Author: rxwei

include/swift/AST/AutoDiff.h

@@ -1,4 +1,4 @@
-//===--- AutoDiff.h - Swift Automatic Differentiation ---------------------===//
+//===--- AutoDiff.h - Swift Differentiable Programming --------------------===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -11,7 +11,8 @@
 //===----------------------------------------------------------------------===//
 //
 //  SWIFT_ENABLE_TENSORFLOW
-//  This file defines AST support for automatic differentiation.
+//  This file defines AST support for the experimental differentiable
+//  programming feature.
 //
 //===----------------------------------------------------------------------===//
 

lib/AST/AutoDiff.cpp

@@ -1,4 +1,4 @@
-//===--- AutoDiff.cpp - Swift Automatic Differentiation -------------------===//
+//===--- AutoDiff.cpp - Swift Differentiable Programming ------------------===//
 //
 // This source file is part of the Swift.org open source project
 //

unittests/AST/AutoDiffIndexSubsetTests.cpp

@@ -71,6 +71,50 @@ TEST(AutoDiffIndexSubset, Equality) {
                                      /*indices*/ {}));
 }
 
+TEST(AutoDiffIndexSubset, Initializers) {
+  TestContext ctx;
+  // Default init.
+  EXPECT_EQ(AutoDiffIndexSubset::getDefault(ctx.Ctx, /*capacity*/ 5,
+                                            /*includeAll*/ true),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 5,
+                                     /*indices*/ {0, 1, 2, 3, 4}));
+  EXPECT_EQ(AutoDiffIndexSubset::getDefault(ctx.Ctx, /*capacity*/ 5,
+                                            /*includeAll*/ false),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 5, /*indices*/ {}));
+  EXPECT_EQ(AutoDiffIndexSubset::getDefault(ctx.Ctx, /*capacity*/ 0,
+                                            /*includeAll*/ true),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 0,
+                                     /*indices*/ {}));
+  EXPECT_EQ(AutoDiffIndexSubset::getDefault(ctx.Ctx, /*capacity*/ 0,
+                                            /*includeAll*/ false),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 0, /*indices*/ {}));
+  // Bit vector init.
+  {
+    llvm::SmallBitVector bitVec(6);
+    bitVec.set(1, 4);
+    EXPECT_EQ(AutoDiffIndexSubset::get(ctx.Ctx, bitVec),
+              AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 6,
+                                       /*indices*/ {1, 2, 3}));
+  }
+  {
+    llvm::SmallBitVector bitVec(0);
+    EXPECT_EQ(AutoDiffIndexSubset::get(ctx.Ctx, bitVec),
+              AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 0,
+                                       /*indices*/ {}));
+  }
+  // String init.
+  EXPECT_EQ(AutoDiffIndexSubset::getFromString(ctx.Ctx, "SSSSS"),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 5,
+                                     /*indices*/ {0, 1, 2, 3, 4}));
+  EXPECT_EQ(AutoDiffIndexSubset::getFromString(ctx.Ctx, "UUUUU"),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 5, /*indices*/ {}));
+  EXPECT_EQ(AutoDiffIndexSubset::getFromString(ctx.Ctx, "SUSUS"),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 5,
+                                     /*indices*/ {0, 2, 4}));
+  EXPECT_EQ(AutoDiffIndexSubset::getFromString(ctx.Ctx, ""),
+            AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 0, /*indices*/ {}));
+}
+
 TEST(AutoDiffIndexSubset, Bits) {
   TestContext ctx;
   auto *indices1 = AutoDiffIndexSubset::get(ctx.Ctx, /*capacity*/ 5,