[clang] [LLVM][ADT] Add specialization of `DenseMapInfo` for `SourceRange` (PR #174524)

[Victor Chernyakin via cfe-commits]

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@@ -379,6 +379,20 @@ TEST_F(SourceManagerTest, getInvalidBOM) {
             "UTF-32 (LE)");
 }
 
+TEST_F(SourceManagerTest, sourceRangeWorksWithDenseSet) {
+  llvm::DenseSet<SourceRange> Set;
+  SourceRange TestRange = {SourceLocation::getFromRawEncoding(10),
+                           SourceLocation::getFromRawEncoding(11)};
+  ASSERT_EQ(Set.size(), 0U);
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localspook wrote:

Comparing against 0 produces a better error message if the test fails: the actual size of the container will be printed out. Checking `.empty()` on the other hand would only tell you that the container's size isn't zero. 

https://github.com/llvm/llvm-project/pull/174524