[lldb] Turn lldb_private::Status into a value type. (#106163)

This patch removes all of the Set.* methods from Status.

This cleanup is part of a series of patches that make it harder use the
anti-pattern of keeping a long-lives Status object around and updating
it while dropping any errors it contains on the floor.

This patch is largely NFC, the more interesting next steps this enables
is to:
1. remove Status.Clear()
2. assert that Status::operator=() never overwrites an error
3. remove Status::operator=()

Note that step (2) will bring 90% of the benefits for users, and step
(3) will dramatically clean up the error handling code in various
places. In the end my goal is to convert all APIs that are of the form

`    ResultTy DoFoo(Status& error)
`
to

`    llvm::Expected<ResultTy> DoFoo()
`
How to read this patch?

The interesting changes are in Status.h and Status.cpp, all other
changes are mostly

` perl -pi -e 's/\.SetErrorString/ = Status::FromErrorString/g' $(git
grep -l SetErrorString lldb/source)
`
plus the occasional manual cleanup.

1 files changed, 17 insertions, 26 deletions

diff --git a/lldb/source/Expression/IRExecutionUnit.cpp b/lldb/source/Expression/IRExecutionUnit.cpp
index f22070442362..d2f2ee26fd43 100644
--- a/lldb/source/Expression/IRExecutionUnit.cpp
+++ b/lldb/source/Expression/IRExecutionUnit.cpp
@@ -120,9 +120,8 @@ Status IRExecutionUnit::DisassembleFunction(Stream &stream,
   }
 
   if (func_local_addr == LLDB_INVALID_ADDRESS) {
-    ret.SetErrorToGenericError();
-    ret.SetErrorStringWithFormat("Couldn't find function %s for disassembly",
-                                 m_name.AsCString());
+    ret = Status::FromErrorStringWithFormat(
+        "Couldn't find function %s for disassembly", m_name.AsCString());
     return ret;
   }
 
@@ -136,9 +135,8 @@ Status IRExecutionUnit::DisassembleFunction(Stream &stream,
   func_range = GetRemoteRangeForLocal(func_local_addr);
 
   if (func_range.first == 0 && func_range.second == 0) {
-    ret.SetErrorToGenericError();
-    ret.SetErrorStringWithFormat("Couldn't find code range for function %s",
-                                 m_name.AsCString());
+    ret = Status::FromErrorStringWithFormat(
+        "Couldn't find code range for function %s", m_name.AsCString());
     return ret;
   }
 
@@ -147,8 +145,7 @@ Status IRExecutionUnit::DisassembleFunction(Stream &stream,
 
   Target *target = exe_ctx.GetTargetPtr();
   if (!target) {
-    ret.SetErrorToGenericError();
-    ret.SetErrorString("Couldn't find the target");
+    ret = Status::FromErrorString("Couldn't find the target");
     return ret;
   }
 
@@ -161,9 +158,8 @@ Status IRExecutionUnit::DisassembleFunction(Stream &stream,
                       buffer_sp->GetByteSize(), err);
 
   if (!err.Success()) {
-    ret.SetErrorToGenericError();
-    ret.SetErrorStringWithFormat("Couldn't read from process: %s",
-                                 err.AsCString("unknown error"));
+    ret = Status::FromErrorStringWithFormat("Couldn't read from process: %s",
+                                            err.AsCString("unknown error"));
     return ret;
   }
 
@@ -175,16 +171,14 @@ Status IRExecutionUnit::DisassembleFunction(Stream &stream,
       Disassembler::FindPlugin(arch, flavor_string, plugin_name);
 
   if (!disassembler_sp) {
-    ret.SetErrorToGenericError();
-    ret.SetErrorStringWithFormat(
+    ret = Status::FromErrorStringWithFormat(
         "Unable to find disassembler plug-in for %s architecture.",
         arch.GetArchitectureName());
     return ret;
   }
 
   if (!process) {
-    ret.SetErrorToGenericError();
-    ret.SetErrorString("Couldn't find the process");
+    ret = Status::FromErrorString("Couldn't find the process");
     return ret;
   }
 
@@ -215,8 +209,7 @@ struct IRExecDiagnosticHandler : public llvm::DiagnosticHandler {
     if (DI.getSeverity() == llvm::DS_Error) {
       const auto &DISM = llvm::cast<llvm::DiagnosticInfoSrcMgr>(DI);
       if (err && err->Success()) {
-        err->SetErrorToGenericError();
-        err->SetErrorStringWithFormat(
+        *err = Status::FromErrorStringWithFormat(
             "IRExecution error: %s",
             DISM.getSMDiag().getMessage().str().c_str());
       }
@@ -241,9 +234,9 @@ void IRExecutionUnit::GetRunnableInfo(Status &error, lldb::addr_t &func_addr,
   func_end = LLDB_INVALID_ADDRESS;
 
   if (!process_sp) {
-    error.SetErrorToGenericError();
-    error.SetErrorString("Couldn't write the JIT compiled code into the "
-                         "process because the process is invalid");
+    error =
+        Status::FromErrorString("Couldn't write the JIT compiled code into the "
+                                "process because the process is invalid");
     return;
   }
 
@@ -299,9 +292,8 @@ void IRExecutionUnit::GetRunnableInfo(Status &error, lldb::addr_t &func_addr,
   m_execution_engine_up.reset(builder.create(target_machine));
 
   if (!m_execution_engine_up) {
-    error.SetErrorToGenericError();
-    error.SetErrorStringWithFormat("Couldn't JIT the function: %s",
-                                   error_string.c_str());
+    error = Status::FromErrorStringWithFormat("Couldn't JIT the function: %s",
+                                              error_string.c_str());
     return;
   }
 
@@ -364,8 +356,7 @@ void IRExecutionUnit::GetRunnableInfo(Status &error, lldb::addr_t &func_addr,
     }
 
     if (!fun_ptr) {
-      error.SetErrorToGenericError();
-      error.SetErrorStringWithFormat(
+      error = Status::FromErrorStringWithFormat(
           "'%s' was in the JITted module but wasn't lowered",
           function.getName().str().c_str());
       return;
@@ -434,7 +425,7 @@ void IRExecutionUnit::GetRunnableInfo(Status &error, lldb::addr_t &func_addr,
     ss.PutCString(
         "\nHint: The expression tried to call a function that is not present "
         "in the target, perhaps because it was optimized out by the compiler.");
-    error.SetErrorString(ss.GetString());
+    error = Status(ss.GetString().str());
 
     return;
   }