[clang] [clang][transformer] Add `merge` range-selector for selecting the merge of two ranges. (PR #169560)

[Yitzhak Mandelbaum via cfe-commits]

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@@ -327,6 +327,38 @@ TEST(RangeSelectorTest, EncloseOpGeneralParsed) {
   EXPECT_THAT_EXPECTED(select(*R, Match), HasValue("3, 7"));
 }
 
+TEST(RangeSelectorTest, MergeOp) {
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ymand wrote:

Please add tests to:
1. exercise cases which mix token and char ranges
2. merge 2 non-contiguous ranges, like `node("a0")` and `node("a2")`

https://github.com/llvm/llvm-project/pull/169560