[clang] [clang][modules] Move `SLocEntry` search into `ASTReader` (PR #66966)

[Ben Langmuir via cfe-commits]

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@@ -50,6 +50,7 @@ int y = a2<int>;
 // CHECK: In module 'a':
 // CHECK-NEXT: a.h:1:45: error:
 
+int z = b<int>;
 // MISSING-B: could not find file '{{.*}}b.h'
 // MISSING-B-NOT: please delete the module cache
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benlangmuir wrote:

Can we use this approach to test the current change? ie. create a version of this test that doesn't deserialize b and therefore doesn't get the diagnostic? You could maybe add more files that don't get deserialized and check that none of them show up to improve the robustness of the test?

https://github.com/llvm/llvm-project/pull/66966