[clang] Add warning for blocks capturing {'this', raw pointers, references} (PR #144388)

[John McCall via cfe-commits]

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@@ -1641,6 +1641,17 @@ def warn_implicitly_retains_self : Warning <
   "block implicitly retains 'self'; explicitly mention 'self' to indicate "
   "this is intended behavior">,
   InGroup<DiagGroup<"implicit-retain-self">>, DefaultIgnore;
+def warn_blocks_capturing_this : Warning<"block implicitly captures 'this'">,
+                                 InGroup<DiagGroup<"blocks-capturing-this">>,
+                                 DefaultIgnore;
+def warn_blocks_capturing_reference
+    : Warning<"block implicitly captures a C++ reference">,
+      InGroup<DiagGroup<"blocks-capturing-reference">>,
+      DefaultIgnore;
+def warn_blocks_capturing_raw_pointer
+    : Warning<"block implicitly captures a raw pointer">,
+      InGroup<DiagGroup<"blocks-capturing-raw-pointer">>,
+      DefaultIgnore;
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rjmccall wrote:

There's an existing `block-capture-autoreleasing` warning group that's probably the right pattern for these group names.

We can also create a diagnostic group that includes all of these warnings. I'm not sure if that's a good idea because of my concerns above, but I state it for completeness.

https://github.com/llvm/llvm-project/pull/144388