[PATCH] D116775: [clang][#47272] Avoid suggesting deprecated version of a declaration over another in typo correction

[Arthur O'Dwyer via Phabricator via cfe-commits]

Quuxplusone requested changes to this revision.
Quuxplusone added inline comments.
This revision now requires changes to proceed.


================
Comment at: clang/lib/Sema/SemaLookup.cpp:4345
+      return;
     }
   }
----------------
It seems like this code is overdue for a "compare these two corrections" //predicate//. The simple version would be
```
auto IsBetter = [&](const TypoCorrection& TC1, const TypoCorrection& TC2) {
    std::pair<bool, std::string> Key1 = { IsDeprecated(TC1.getFoundDecl()), TC1.getAsString(SemaRef.getLangOpts()) };
    std::pair<bool, std::string> Key2 = { IsDeprecated(TC2.getFoundDecl()), TC2.getAsString(SemaRef.getLangOpts()) };
    return Key1 < Key2;  // prefer non-deprecated, alphabetically earlier declarations
};
for (TypoCorrection& TC : CList) {
    if (IsBetter(Correction, TC))
        TC = Correction;
}
```
Actually, you could even replicate the hoisting of the loop-invariant stuff, the way the old code did:
```
std::pair<bool, std::string> CorrectionKey = { IsDeprecated(Correction.getFoundDecl()), Correction.getAsString(SemaRef.getLangOpts()) };
auto CorrectionIsBetterThan = [&](const TypoCorrection& TC) {
    std::pair<bool, std::string> Key = { IsDeprecated(TC.getFoundDecl()), TC.getAsString(SemaRef.getLangOpts()) };
    return CorrectionKey < Key;  // prefer non-deprecated, alphabetically earlier declarations
};
for (TypoCorrection& TC : CList) {
    if (CorrectionIsBetterThan(TC))
        TC = Correction;
}
```


================
Comment at: clang/test/SemaCXX/typo-correction.cpp:764-769
+namespace Views {
+int Take(); // expected-note{{'Views::Take' declared here}}
+}
+namespace [[deprecated("use Views instead")]] View {
+using Views::Take;
+}
----------------
I suggest //three// namespaces, named `[[deprecated]] A`, `B`, and `[[deprecated]] C`, and declared in that lexical order too, so that no matter how the preference predicate is expressed, we're still testing that the non-deprecated (middle) declaration gets chosen.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D116775/new/

https://reviews.llvm.org/D116775