[Symbol] Use llvm::Expected when getting TypeSystems

Summary:
This commit achieves the following:
- Functions used to return a `TypeSystem *` return an
  `llvm::Expected<TypeSystem *>` now. This means that the result of a call
  is always checked, forcing clients to move more carefully.
- `TypeSystemMap::GetTypeSystemForLanguage` will either return an Error or a
  non-null pointer to a TypeSystem.

Reviewers: JDevlieghere, davide, compnerd

Subscribers: jdoerfert, lldb-commits

Differential Revision: https://reviews.llvm.org/D65122

llvm-svn: 367360

1 files changed, 5 insertions, 2 deletions

diff --git a/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h b/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h
index 68036360686..7eb86576500 100644
--- a/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h
+++ b/lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h
@@ -118,8 +118,11 @@ public:
   size_t FindTypes(const std::vector<CompilerContext> &context, bool append,
                    TypeMap &types) override;
 
-  TypeSystem *GetTypeSystemForLanguage(lldb::LanguageType language) override {
-    return nullptr;
+  llvm::Expected<TypeSystem &>
+  GetTypeSystemForLanguage(lldb::LanguageType language) override {
+    return llvm::make_error<llvm::StringError>(
+        "SymbolFileBreakpad does not support GetTypeSystemForLanguage",
+        llvm::inconvertibleErrorCode());
   }
 
   CompilerDeclContext