[PATCH] D106394: [clang][pp] adds '#pragma include_instead'

[Christopher Di Bella via Phabricator via cfe-commits]

cjdb added a comment.

Thanks for the first pass @aaron.ballman! Some clarifying questions, but I think I have enough of your other comments to work on while you ponder these.



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Comment at: clang/include/clang/Basic/DiagnosticLexKinds.td:303
   InGroup<DiagGroup<"pragma-system-header-outside-header">>;
+def pp_pragma_include_instead_not_sysheader : Warning<
+  "'#pragma include_instead' ignored outside of system headers">,
----------------
aaron.ballman wrote:
> Design-wise, do we want this one to be an error instead of a warning? I don't have strong feelings one way or the other, but making it an error ensures no one finds creative ways to use it outside of a system header by accident (and we can relax the restriction later if there are reasons to do so).
I'd prefer it to be an error, but I wasn't confident that would be accepted (same applies to all your comments re warn vs err). If you're game, I'll make the change.


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Comment at: clang/include/clang/Basic/DiagnosticLexKinds.td:306
+  InGroup<PragmaIncludeInstead>,
+  ShowInSystemHeader;
+def pp_pragma_include_instead_unexpected_token : Warning<
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aaron.ballman wrote:
> O.o... why do we need to show this one in system headers if the diagnostic can only trigger outside of a system header?
Mostly because I'm scared that there's some toggle that would accidentally make the diagnostic observable in a system header and wanted to test the behaviour.


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Comment at: clang/lib/Lex/PPLexerChange.cpp:316
+    const StringRef Filename = Include.getKey();
+    const auto &IncludeInfo = Include.getValue();
+    const HeaderFileInfo &Info = HeaderInfo.getFileInfo(IncludeInfo.File);
----------------
aaron.ballman wrote:
> Please spell out the type.
The type's currently a private type (that was by design). Do you want me to make it a public type or pull it out into `namespace clang`?


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Comment at: clang/lib/Lex/Pragma.cpp:559
+    Diag(Tok, diag::pp_pragma_include_instead_unexpected_token)
+        << "(" << (spelling == "\n" ? "\\n" : spelling);
+    return;
----------------
I thought I deleted this.


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Comment at: clang/lib/Lex/Pragma.cpp:572
+  if (Tok.isNot(tok::r_paren)) {
+    const std::string spelling = getSpelling(Tok);
+    Diag(Tok, diag::pp_pragma_include_instead_unexpected_token)
----------------
aaron.ballman wrote:
> 
Alternatively: remove `spelling` altogether.


Repository:
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  https://reviews.llvm.org/D106394/new/

https://reviews.llvm.org/D106394