[lld-macho] Demangle symbol names in duplicate-symbol error when -demangle is specified

[thakis]

Thanks :)

[int3]

Nice!

lld/MachO/SymbolTable.cpp

if (auto *defined = dyn_cast<Defined>(s)) {
       if (defined->isWeakDef()) {
         // FIXME: Handle this for bitcode files.
         if (auto concatIsec =
                 dyn_cast_or_null<ConcatInputSection>(defined->isec)) {
           concatIsec->wasCoalesced = true;
           concatIsec->symbols.erase(llvm::find(concatIsec->symbols, defined));
         }
       } else {
-        error("duplicate symbol: " + name + "\n>>> defined in " +
+        error("duplicate symbol: " + toString(*defined) + "\n>>> defined in " +
               toString(defined->getFile()) + "\n>>> defined in " +
               toString(file));
       }
 
     } else if (auto *dysym = dyn_cast<DylibSymbol>(s)) {
       overridesWeakDef = !isWeakDef && dysym->isWeakDef();
       dysym->unreference();
     }

lld/test/MachO/invalid/duplicate-symbol.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t-dup.o
-# RUN: not %lld -o /dev/null %t-dup.o %t.o 2>&1 | FileCheck %s -DFILE_1=%t-dup.o -DFILE_2=%t.o
-# RUN: not %lld -o /dev/null %t.o %t.o 2>&1 | FileCheck %s -DFILE_1=%t.o -DFILE_2=%t.o
+# RUN: not %lld -dylib -o /dev/null %t-dup.o %t.o 2>&1 | FileCheck %s -DNAME=_ZN1a1bL3fooE -DFILE_1=%t-dup.o -DFILE_2=%t.o
+# RUN: not %lld -dylib -o /dev/null %t.o %t.o 2>&1 | FileCheck %s -DNAME=_ZN1a1bL3fooE -DFILE_1=%t.o -DFILE_2=%t.o
 
-# CHECK:      error: duplicate symbol: _main
+# RUN: not %lld -dylib -demangle -o /dev/null %t-dup.o %t.o 2>&1 | FileCheck %s -DNAME="a::b::foo" -DFILE_1=%t-dup.o -DFILE_2=%t.o
+# RUN: not %lld -dylib -demangle -o /dev/null %t.o %t.o 2>&1 | FileCheck %s -DNAME="a::b::foo" -DFILE_1=%t.o -DFILE_2=%t.o
+
+# CHECK:      error: duplicate symbol: [[NAME]]
 # CHECK-NEXT: >>> defined in [[FILE_1]]
 # CHECK-NEXT: >>> defined in [[FILE_2]]
 
 .text
-.global _main
-_main:
-  mov $0, %rax
+.global _ZN1a1bL3fooE
+_ZN1a1bL3fooE:
   ret