[PATCH] D13157: Teach -Wtautological-overlap-compare about enums

[Richard Trieu via cfe-commits]

rtrieu added a comment.

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================
Comment at: lib/Analysis/CFG.cpp:99-104
@@ +98,8 @@
+  // Currently we're only given EnumConstantDecls or IntegerLiterals
+  auto *C1 = cast<EnumConstantDecl>(cast<DeclRefExpr>(A)->getDecl());
+  auto *C2 = cast<EnumConstantDecl>(cast<DeclRefExpr>(B)->getDecl());
+
+  const TagDecl *E1 = TagDecl::castFromDeclContext(C1->getDeclContext());
+  const TagDecl *E2 = TagDecl::castFromDeclContext(C2->getDeclContext());
+  return E1 == E2;
+}
----------------
george.burgess.iv wrote:
> rtrieu wrote:
> > There's a few extra casts in here, plus some blind conversions between types.  Add your assumptions for the types in asserts.  Also, DeclContext should use cast<> to get to Decl types.  I recommend the following:
> > 
> > ```
> >   assert(isa<DeclRefExpr>(E1) && isa<DeclRefExpr>(E2));
> >   auto *Decl1 = cast<DeclRefExpr>(E1)->getDecl();
> >   auto *Decl2 = cast<DeclRefExpr>(E2)->getDecl();
> > 
> >   assert(isa<EnumConstantDecl>(Decl1) && isa<EnumConstantDecl>(Decl2));
> >   const DeclContext *DC1 = Decl1->getDeclContext();
> >   const DeclContext *DC2 = Decl2->getDeclContext();
> > 
> >   assert(isa<EnumDecl>(DC1) && isa<EnumDecl>(DC2));
> >   return DC1 == DC2;
> > 
> > ```
> I was under the impression that the `cast<Foo>(Bar)` asserts `isa<Foo>(Bar)` for me, so I thought that asserts like those would just be redundant. Changed to your version anyway :)
You are correct, 'cast<Foo>(Bar)' does assert 'isa<Foo>(Bar)'.  However, when Bar is not Foo, using the assert here means the crash will produce a backtrace will point straight to this function instead of an assert that points deep into the casting functions.


http://reviews.llvm.org/D13157