[projection] Add non-supported projection users to the non projection user list.

Otherwise when we try to rewrite uses, we will run into one of these
values. Since ProjectionTree won't know how to deal with those, we will crash.

rdar://41146023
(cherry picked from commit 9bba338)

Author: gottesmm

lib/SIL/Projection.cpp

@@ -840,6 +840,24 @@ createProjection(SILBuilder &B, SILLocation Loc, SILValue Arg) const {
   return Proj->createProjection(B, Loc, Arg);
 }
 
+// Projection tree only supports structs and tuples today.
+static bool isSupportedProjection(const Projection &p) {
+  switch (p.getKind()) {
+  case ProjectionKind::Struct:
+  case ProjectionKind::Tuple:
+    return true;
+  case ProjectionKind::Class:
+  case ProjectionKind::Enum:
+  case ProjectionKind::Box:
+  case ProjectionKind::Upcast:
+  case ProjectionKind::RefCast:
+  case ProjectionKind::BitwiseCast:
+  case ProjectionKind::TailElems:
+  case ProjectionKind::Index:
+    return false;
+  }
+}
+
 void
 ProjectionTreeNode::
 processUsersOfValue(ProjectionTree &Tree,
@@ -863,12 +881,11 @@ processUsersOfValue(ProjectionTree &Tree,
       continue;
     }
 
-    // Check whether the user is such a projection.
     auto P = Projection(projectionInst);
 
-    // If we fail to create a projection, add User as a user to this node and
-    // continue.
-    if (!P.isValid()) {
+    // If we fail to create a projection or this is a type of projection that we
+    // do not support, add User as a user to this node and continue.
+    if (!P.isValid() || !isSupportedProjection(P)) {
       DEBUG(llvm::dbgs() << "            Failed to create projection. Adding "
             "to non projection user!\n");
       addNonProjectionUser(Op);