Add ConstString test FromMidOfBufferStringRef

[sgraenitz]

Summary

It was not immediately clear to me whether or not non-null-terminated StringRef's are supported in ConstString and/or the counterpart mechanism. From this test it seems to be fine. Maybe useful to keep?

[labath]

In general, I would assume that a function taking a StringRef can take *any* StringRef object (including the non-terminated ones), unless the limitations are very clearly documented.

That said, having a test that verifies this is a legitimate thing, and since you've already written one, we might as well check it in.

unittests/Utility/ConstStringTest.cpp

TEST(ConstStringTest, MangledCounterpart) {
 
   EXPECT_TRUE(bar.GetMangledCounterpart(counterpart));
   EXPECT_EQ("foo", counterpart.GetStringRef());
 
   EXPECT_TRUE(foo.GetMangledCounterpart(counterpart));
   EXPECT_EQ("bar", counterpart.GetStringRef());
 }
 
+TEST(ConstStringTest, FromMidOfBufferStringRef) {
+  // StringRef's into bigger buffer: no null termination
+  const char *buffer = "foobarbaz";
+  llvm::StringRef foo_ref(buffer, 3);
+  llvm::StringRef bar_ref(buffer + 3, 3);
+
+  ConstString foo(foo_ref);
+
+  ConstString bar;
+  bar.SetStringWithMangledCounterpart(bar_ref, foo);
+  EXPECT_EQ("bar", bar.GetStringRef());
+
+  ConstString counterpart;
+  EXPECT_TRUE(bar.GetMangledCounterpart(counterpart));
+  EXPECT_EQ("foo", counterpart.GetStringRef());
+
+  EXPECT_TRUE(foo.GetMangledCounterpart(counterpart));
+  EXPECT_EQ("bar", counterpart.GetStringRef());
+}
+
 TEST(ConstStringTest, NullAndEmptyStates) {
   ConstString foo("foo");
   EXPECT_FALSE(!foo);
   EXPECT_FALSE(foo.IsEmpty());
   EXPECT_FALSE(foo.IsNull());
 
   ConstString empty("");
   EXPECT_TRUE(!empty);
   EXPECT_TRUE(empty.IsEmpty());
   EXPECT_FALSE(empty.IsNull());
 
   ConstString null;
   EXPECT_TRUE(!null);
   EXPECT_TRUE(null.IsEmpty());
   EXPECT_TRUE(null.IsNull());
 }