[clang] [NFC] Factor out common parts of ArraySections into its own class (PR #89639)

[Erich Keane via cfe-commits]

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@@ -11163,7 +11163,7 @@ def err_omp_declare_mapper_redefinition : Error<
   "redefinition of user-defined mapper for type %0 with name %1">;
 def err_omp_invalid_mapper: Error<
   "cannot find a valid user-defined mapper for type %0 with name %1">;
-def err_omp_array_section_use : Error<"OpenMP array section is not allowed here">;
+def err_array_section_use : Error<"array section is not allowed here">;
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erichkeane wrote:

I generalized this diagnostic as well, though I see I could PERHAPS get this right based on the type of the Expression above.  WDYT?

https://github.com/llvm/llvm-project/pull/89639