[clang] Warning for incorrect useof 'pure' attribute (PR #78200)

[Erich Keane via cfe-commits]

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@@ -692,6 +692,13 @@ def warn_maybe_falloff_nonvoid_function : Warning<
 def warn_falloff_nonvoid_function : Warning<
   "non-void function does not return a value">,
   InGroup<ReturnType>;
+def warn_const_attr_with_pure_attr : Warning<
+  "'const' attribute imposes more restrictions, 'pure' attribute ignored">,
+  InGroup<IgnoredAttributes>;
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erichkeane wrote:

I think the changes made here are sufficiently closely related, they are definitely 'near the line', but are sufficiently close (in that it is fixing up teh diagnostics for the pure/const attributes).

https://github.com/llvm/llvm-project/pull/78200