show compile error trace

src/backend/mxnet/graph.jl

@@ -79,3 +79,22 @@ function tograph(model, args...)
   out = interp(ctx, model, map(constant, args)...)
   return ctx[:params], ctx[:stacks], out
 end
+
+# Error Handling
+
+function errnode(e::mx.MXError)
+  m = match(r"Error in (\w+):", e.msg)
+  m == nothing && return
+  Symbol(m.captures[1])
+end
+
+macro mxerr(stk, ex)
+  :(try
+      $(esc(ex))
+    catch e
+      (isa(e, mx.MXError) && (node = errnode(e)) != nothing) || rethrow()
+      stk = $(esc(stk))
+      @show stk[node]
+      rethrow()
+    end)
+end

src/backend/mxnet/model.jl

@@ -37,10 +37,10 @@ function mxnet(model::Model, input)
   params, stacks, node = tograph(model, mx.Variable(:input))
   args = merge(mxargs(params), Dict(:input => mx.zeros(input)))
   grads = mxgrads(args)
-  model = MXModel(model, params, grads, stacks,
-                  mx.bind(node, args = args,
-                                args_grad = grads,
-                                grad_req = mx.GRAD_ADD))
+  model = @mxerr stacks MXModel(model, params, grads, stacks,
+                                mx.bind(node, args = args,
+                                              args_grad = grads,
+                                              grad_req = mx.GRAD_ADD))
   loadparams!(model)
   return model
 end