Make forceouterctx more forgiving

* Try going for an outer frame if the immediately available one is
  inlined (this will work together with a change in Rakudo to mark
  frames that use `EVAL` as no-inline, and mean that `try EVAL $x`
  will work out fine)
* If that doesn't work, don't SEGV, but throw

src/6model/reprs/MVMContext.c

@@ -346,6 +346,23 @@ MVMFrame * MVM_context_get_frame(MVMThreadContext *tc, MVMContext *ctx) {
     return result;
 }
 
+/* Resolves the context to an exact frame; if the frame in question is an
+ * inline, takes the inline's outer. Returns NULL if neither resolves. */
+MVMFrame * MVM_context_get_frame_or_outer(MVMThreadContext *tc, MVMContext *ctx) {
+    MVMSpeshFrameWalker fw;
+    MVMFrame *result = NULL;
+    MVM_spesh_frame_walker_init(tc, &fw, ctx->body.context, 0);
+    if (apply_traversals(tc, &fw, ctx->body.traversals, ctx->body.num_traversals)) {
+        result = MVM_spesh_frame_walker_get_frame(tc, &fw);
+        if (!result) {
+            MVM_spesh_frame_walker_move_outer(tc, &fw);
+            result = MVM_spesh_frame_walker_get_frame(tc, &fw);
+        }
+    }
+    MVM_spesh_frame_walker_cleanup(tc, &fw);
+    return result;
+}
+
 /* Resolves the context and gets a hash of its lexicals. */
 MVMObject * MVM_context_lexicals_as_hash(MVMThreadContext *tc, MVMContext *ctx) {
     MVMSpeshFrameWalker fw;

src/6model/reprs/MVMContext.h

@@ -33,6 +33,7 @@ const MVMREPROps * MVMContext_initialize(MVMThreadContext *tc);
 MVM_PUBLIC MVMObject * MVM_context_from_frame(MVMThreadContext *tc, MVMFrame *f);
 MVMObject * MVM_context_apply_traversal(MVMThreadContext *tc, MVMContext *ctx, MVMuint8 traversal);
 MVMFrame * MVM_context_get_frame(MVMThreadContext *tc, MVMContext *ctx);
+MVMFrame * MVM_context_get_frame_or_outer(MVMThreadContext *tc, MVMContext *ctx);
 MVMObject * MVM_context_lexicals_as_hash(MVMThreadContext *tc, MVMContext *ctx);
 MVMint64 MVM_context_lexical_primspec(MVMThreadContext *tc, MVMContext *ctx, MVMString *name);
 MVMObject * MVM_context_get_code(MVMThreadContext *tc, MVMContext *ctx);

src/core/interp.c

@@ -2824,7 +2824,9 @@ void MVM_interp_run(MVMThreadContext *tc, void (*initial_invoke)(MVMThreadContex
                     MVM_exception_throw_adhoc(tc, "forceouterctx needs a code ref");
                 if (REPR(ctx)->ID != MVM_REPR_ID_MVMContext || !IS_CONCRETE(ctx))
                     MVM_exception_throw_adhoc(tc, "forceouterctx needs a context");
-                context = MVM_context_get_frame(tc, (MVMContext *)ctx);
+                context = MVM_context_get_frame_or_outer(tc, (MVMContext *)ctx);
+                if (!context)
+                    MVM_exception_throw_adhoc(tc, "Failed to resolve context for forceouterctx");
 
                 orig = ((MVMCode *)obj)->body.outer;
                 sf = ((MVMCode *)obj)->body.sf;