[clang] [clang] Serialization: support hashing null template arguments (PR #141890)

[Matheus Izvekov via cfe-commits]

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@@ -65,7 +65,9 @@ void TemplateArgumentHasher::AddTemplateArgument(TemplateArgument TA) {
 
   switch (Kind) {
   case TemplateArgument::Null:
-    llvm_unreachable("Expected valid TemplateArgument");
+    // These can occur in incomplete substitutions performed with code
+    // completion (see PartialOverloading).
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mizvekov wrote:

I think this name is the best stable reference to this functionality.
And I don't think mentioning file names is a good idea, and there is no documentation to point to.

Is there any specific thing this comment should say so you think this would be easier to find?

https://github.com/llvm/llvm-project/pull/141890