[Error] Add non-consuming toString (#95375)

There are some places that want to convert an Error to string, but still
retain the original Error object, for example to emit a non-fatal
warning.

This currently isn't possible, because the entire Error infra is
move-based. And what people end up doing in this case is to move the
Error... twice.

This patch introduces a toStringWithoutConsuming() function to
accommodate this use case. This also requires some infrastructure that
allows visiting Errors without consuming them.

2 files changed, 4 insertions, 4 deletions

diff --git a/llvm/tools/dsymutil/DwarfLinkerForBinary.cpp b/llvm/tools/dsymutil/DwarfLinkerForBinary.cpp
index 8347370..f6a3570 100644
--- a/llvm/tools/dsymutil/DwarfLinkerForBinary.cpp
+++ b/llvm/tools/dsymutil/DwarfLinkerForBinary.cpp
@@ -147,7 +147,7 @@ DwarfLinkerForBinary::loadObject(const DebugMapObject &Obj,
   if (!ObjectEntry) {
     auto Err = ObjectEntry.takeError();
     reportWarning(Twine(Obj.getObjectFilename()) + ": " +
-                      toString(std::move(Err)),
+                      toStringWithoutConsuming(Err),
                   Obj.getObjectFilename());
     return errorToErrorCode(std::move(Err));
   }
@@ -156,7 +156,7 @@ DwarfLinkerForBinary::loadObject(const DebugMapObject &Obj,
   if (!Object) {
     auto Err = Object.takeError();
     reportWarning(Twine(Obj.getObjectFilename()) + ": " +
-                      toString(std::move(Err)),
+                      toStringWithoutConsuming(Err),
                   Obj.getObjectFilename());
     return errorToErrorCode(std::move(Err));
   }
diff --git a/llvm/tools/llvm-pdbutil/DumpOutputStyle.cpp b/llvm/tools/llvm-pdbutil/DumpOutputStyle.cpp
index 1cecbfc..b2362ec 100644
--- a/llvm/tools/llvm-pdbutil/DumpOutputStyle.cpp
+++ b/llvm/tools/llvm-pdbutil/DumpOutputStyle.cpp
@@ -1494,13 +1494,13 @@ Error DumpOutputStyle::dumpModuleSymsForPdb() {
           if (auto EC = Visitor.visitSymbolStreamFiltered(ModS.getSymbolArray(),
                                                           Filter)) {
             P.formatLine("Error while processing symbol records.  {0}",
-                         toString(std::move(EC)));
+                         toStringWithoutConsuming(EC));
             return EC;
           }
         } else if (auto EC = Visitor.visitSymbolStream(ModS.getSymbolArray(),
                                                        SS.Offset)) {
           P.formatLine("Error while processing symbol records.  {0}",
-                       toString(std::move(EC)));
+                       toStringWithoutConsuming(EC));
           return EC;
         }
         return Error::success();