[clang] [Serialization] Fix lazy template loading (PR #133057)

[Jonas Hahnfeld via cfe-commits]

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@@ -367,12 +367,6 @@ bool RedeclarableTemplateDecl::loadLazySpecializationsImpl(
   if (!ExternalSource)
     return false;
 
-  // If TPL is not null, it implies that we're loading specializations for
-  // partial templates. We need to load all specializations in such cases.
-  if (TPL)
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hahnjo wrote:

Actually, looking into df061c3e2b97974f9e2d72a023eb1c5b987010bc this may be something which is not properly handled for lazy template loading. @emaxx-google can you check if the failures you are seeing involves constrained partial specializations or function overloads? If so, can you mayble locally revert 48f50c7385d79da320cdf52d3aabc83cc403ff9c `[Serialization] Load only needed partial specializations`?

https://github.com/llvm/llvm-project/pull/133057