[NFC] IRGen: Added debugging info.

In debug builds, provide some context when an archetype fails to be
found.

Author: nate-chandler

lib/IRGen/GenArchetype.cpp

@@ -48,6 +48,7 @@
 #include "IRGenDebugInfo.h"
 #include "IRGenFunction.h"
 #include "IRGenModule.h"
+#include "LocalTypeData.h"
 #include "MetadataRequest.h"
 #include "Outlining.h"
 #include "ProtocolInfo.h"
@@ -75,6 +76,25 @@ irgen::emitArchetypeTypeMetadataRef(IRGenFunction &IGF,
       return emitOpaqueTypeMetadataRef(IGF, opaque, request);
   }
 
+#ifndef NDEBUG
+  if (!archetype->getParent()) {
+    llvm::errs() << "Metadata for archetype not bound in function.\n"
+                 << "  The metadata could be missing entirely because it needs "
+                    "to be passed to the function.\n"
+                 << "  Or the metadata is present and not bound in which case "
+                    "setScopedLocalTypeMetadata or similar must be called.\n";
+    llvm::errs() << "Archetype without metadata: " << archetype << "\n";
+    archetype->dump(llvm::errs());
+    llvm::errs() << "Function:\n";
+    IGF.CurFn->print(llvm::errs());
+    if (auto localTypeData = IGF.getLocalTypeData()) {
+      llvm::errs() << "LocalTypeData:\n";
+      localTypeData->dump();
+    } else {
+      llvm::errs() << "No LocalTypeDataCache for this function!\n";
+    }
+  }
+#endif
   // If there's no local or opaque metadata, it must be a nested type.
   assert(archetype->getParent() && "Not a nested archetype");
 

lib/IRGen/IRGenFunction.h

@@ -792,6 +792,9 @@ class IRGenFunction {
   llvm::Value *getDynamicSelfMetadata();
   void setDynamicSelfMetadata(CanType selfBaseTy, bool selfIsExact,
                               llvm::Value *value, DynamicSelfKind kind);
+#ifndef NDEBUG
+  LocalTypeDataCache const *getLocalTypeData() { return LocalTypeData; }
+#endif
 
 private:
   LocalTypeDataCache &getOrCreateLocalTypeData();