[LLVMbugs] [Bug 13110] New: Should warn for "const" applied to reference type (even a typedef)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13110

             Bug #: 13110
           Summary: Should warn for "const" applied to reference type
                    (even a typedef)
           Product: clang
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: arthur.j.odwyer at gmail.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


cat >test.cc <<EOF
typedef int& IntRef;
void foo(const IntRef m);
void bar(int& const m);
EOF
clang++ -W -Wall -Wextra -c test.cc

test.cc:3:15: error: 'const' qualifier may not be applied to a reference
void bar(int& const m);
              ^
1 error generated.

I see why it's useful to have the qualifier on "const T" be silently ignored
when T is a template type parameter, but wouldn't it be helpful and non-hurtful
for Clang to give a non-fatal warning message in the above case, where T is
merely a typedef?

A quick Google search will turn up more than a handful of frequently asked
questions from C++ newbies asking why "const IntRef" doesn't mean the same
thing as "const int &". And then when they hear the answer ("reference types
can't be const-qualified"), they'll usually follow up with "whoa, why does the
compiler allow me to type that at all, then?" And then the thread dies because
there's really no good answer to that.

Could Clang be the first compiler to diagnose this common newbie mistake with a
warning message?

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