rsmith added a comment.
I think a reasonable approach would be: "do not warn on shadowing if the idiom
of naming a constructor parameter after a class member is used, and the class
member is initialized from that constructor parameter, and all uses of the
parameter in the constructor body would still be valid if it were declared
`const`".
In particular, I think we should probably warn if a non-const reference is
bound to the parameter, or if the constructor's member initializer list does
not contain `field(field)`.
(I agree that catching `A(X x) : x(std::move(x)) { use(x); }` is outside the
scope of this change.)
================
Comment at: lib/Sema/SemaDecl.cpp:6400
@@ +6399,3 @@
+ if (isa<CXXConstructorDecl>(NewDC) && isa<ParmVarDecl>(D))
+ return;
+ }
----------------
Instead of redoing class member lookup every time we check to see if a variable
is modifiable, perhaps you could populate a set of shadowed-but-not-diagnosed
`VarDecl*`s here? That way, you can also suppress the duplicate diagnostics if
the variable is modified multiple times by removing it from the set.
================
Comment at: lib/Sema/SemaExpr.cpp:9663
@@ +9662,3 @@
+ if (!S.getLangOpts().CPlusPlus ||
+ S.Diags.isIgnored(diag::warn_decl_shadow, Loc))
+ return;
----------------
This query is actually quite expensive (more so than some or all of the other
checks below).
http://reviews.llvm.org/D18271
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