Debug Info: Only bind the archetypes referenced by variable types early

at -Onone.

Thanks to rjmccall for the feedback!

Author: adrian-prantl

lib/IRGen/IRGenSIL.cpp

@@ -652,9 +652,14 @@ class IRGenSILFunction :
                                     StringRef Name,
                                     unsigned ArgNo = 0,
                                     IndirectionKind Indirection = DirectValue) {
-    // Eagerly load the type metadata at -Onone.
-    if (!IGM.Opts.Optimize && SILTy && SILTy.hasArchetype())
-      emitTypeMetadataRefForLayout(SILTy);
+    // Force all archetypes referenced by the type to be bound by this point.
+    // TODO: just make sure that we have a path to them that the debug info
+    //       can follow.
+    if (!IGM.Opts.Optimize && Ty.getType()->hasArchetype())
+      Ty.getType()->getCanonicalType().visit([&](Type t) {
+        if (auto archetype = dyn_cast<ArchetypeType>(CanType(t)))
+          emitTypeMetadataRef(archetype);
+       });
 
     assert(IGM.DebugInfo && "debug info not enabled");
     if (ArgNo) {

test/DebugInfo/EagerTypeMetadata.swift

@@ -9,7 +9,7 @@ public class C<T>
     // CHECK: %T = load %swift.type*, %swift.type**
     // CHECK-SAME: !dbg ![[LOC:[0-9]+]], !invariant.load
     // CHECK: ![[LOC]] = !DILocation(line: 0,
-    var x = i
+    var x = [i]
   }
 }