diff --git a/src/librustc/ty/layout.rs b/src/librustc/ty/layout.rs
index 75600ddaabdb5..ff95554dbbfcd 100644
--- a/src/librustc/ty/layout.rs
+++ b/src/librustc/ty/layout.rs
@@ -20,7 +20,8 @@ use ty::{self, Ty, TyCtxt, TypeFoldable};
 use syntax::ast::{FloatTy, IntTy, UintTy};
 use syntax::attr;
 use syntax_pos::DUMMY_SP;
-use rustc_i128::{i128, u128};
+use rustc_i128::u128;
+use rustc_const_math::ConstInt;
 
 use std::cmp;
 use std::fmt;
@@ -1198,20 +1199,25 @@ impl<'a, 'gcx, 'tcx> Layout {
 
                 if def.is_enum() && def.variants.iter().all(|v| v.fields.is_empty()) {
                     // All bodies empty -> intlike
-                    let (mut min, mut max, mut non_zero) = (i128::max_value(),
-                                                            i128::min_value(),
+                    let (mut min, mut max, mut non_zero) = (i64::max_value(),
+                                                            i64::min_value(),
                                                             true);
                     for v in &def.variants {
-                        let x = v.disr_val.to_u128_unchecked() as i128;
+                        let x = match v.disr_val.erase_type() {
+                            ConstInt::InferSigned(i) => i as i64,
+                            ConstInt::Infer(i) => i as u64 as i64,
+                            _ => bug!()
+                        };
                         if x == 0 { non_zero = false; }
                         if x < min { min = x; }
                         if x > max { max = x; }
                     }
 
-                    // FIXME: should take i128?
+                    // FIXME: should handle i128? signed-value based impl is weird and hard to
+                    // grok.
                     let (discr, signed) = Integer::repr_discr(tcx, ty, &hints[..],
-                                                              min as i64,
-                                                              max as i64);
+                                                              min,
+                                                              max);
                     return success(CEnum {
                         discr: discr,
                         signed: signed,
diff --git a/src/librustc_llvm/ffi.rs b/src/librustc_llvm/ffi.rs
index fb188252075e6..6815da4cc20fd 100644
--- a/src/librustc_llvm/ffi.rs
+++ b/src/librustc_llvm/ffi.rs
@@ -33,7 +33,7 @@ pub enum LLVMRustResult {
 // Consts for the LLVM CallConv type, pre-cast to usize.
 
 /// LLVM CallingConv::ID. Should we wrap this?
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, PartialEq, Debug)]
 #[repr(C)]
 pub enum CallConv {
     CCallConv = 0,
diff --git a/src/librustc_trans/abi.rs b/src/librustc_trans/abi.rs
index 3fba75bc253cd..65e752232f6ad 100644
--- a/src/librustc_trans/abi.rs
+++ b/src/librustc_trans/abi.rs
@@ -313,7 +313,7 @@ impl ArgType {
 ///
 /// I will do my best to describe this structure, but these
 /// comments are reverse-engineered and may be inaccurate. -NDM
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct FnType {
     /// The LLVM types of each argument.
     pub args: Vec<ArgType>,
diff --git a/src/librustc_trans/mir/mod.rs b/src/librustc_trans/mir/mod.rs
index 7a50e5cbe8c79..a1373cb9482b7 100644
--- a/src/librustc_trans/mir/mod.rs
+++ b/src/librustc_trans/mir/mod.rs
@@ -205,6 +205,7 @@ pub fn trans_mir<'a, 'tcx: 'a>(
     sig: &ty::FnSig<'tcx>,
     abi: Abi,
 ) {
+    debug!("fn_ty: {:?}", fn_ty);
     let debug_context =
         debuginfo::create_function_debug_context(fcx.ccx, instance, sig, abi, fcx.llfn, mir);
     let bcx = fcx.get_entry_block();
diff --git a/src/librustc_trans/mir/operand.rs b/src/librustc_trans/mir/operand.rs
index a15d51d9da64d..526155655af27 100644
--- a/src/librustc_trans/mir/operand.rs
+++ b/src/librustc_trans/mir/operand.rs
@@ -79,7 +79,7 @@ impl<'a, 'tcx> OperandRef<'tcx> {
     pub fn immediate(self) -> ValueRef {
         match self.val {
             OperandValue::Immediate(s) => s,
-            _ => bug!()
+            _ => bug!("not immediate: {:?}", self)
         }
     }