From 81e8137b0dc436aad7fda9bffc6b2c2da67a353a Mon Sep 17 00:00:00 2001
From: Mark Simulacrum <mark.simulacrum@gmail.com>
Date: Mon, 2 Jan 2017 13:05:42 -0700
Subject: [PATCH] Inline trans_switch to simplify code

---
 src/librustc_trans/adt.rs  | 28 ----------------------------
 src/librustc_trans/glue.rs | 18 +++++++++++++-----
 2 files changed, 13 insertions(+), 33 deletions(-)

diff --git a/src/librustc_trans/adt.rs b/src/librustc_trans/adt.rs
index 28934407c17..c3b9a56ac97 100644
--- a/src/librustc_trans/adt.rs
+++ b/src/librustc_trans/adt.rs
@@ -56,12 +56,6 @@ use monomorphize;
 use type_::Type;
 use type_of;
 
-#[derive(Copy, Clone, PartialEq)]
-pub enum BranchKind {
-    Switch,
-    Single
-}
-
 /// Given an enum, struct, closure, or tuple, extracts fields.
 /// Treats closures as a struct with one variant.
 /// `empty_if_no_variants` is a switch to deal with empty enums.
@@ -273,28 +267,6 @@ fn struct_llfields<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>, fields: &Vec<Ty<'tcx>>
     }
 }
 
-/// Obtain a representation of the discriminant sufficient to translate
-/// destructuring; this may or may not involve the actual discriminant.
-pub fn trans_switch<'a, 'tcx>(
-    bcx: &Builder<'a, 'tcx>,
-    t: Ty<'tcx>,
-    scrutinee: ValueRef,
-    range_assert: bool
-) -> (BranchKind, Option<ValueRef>) {
-    let l = bcx.ccx.layout_of(t);
-    match *l {
-        layout::CEnum { .. } | layout::General { .. } |
-        layout::RawNullablePointer { .. } | layout::StructWrappedNullablePointer { .. } => {
-            (BranchKind::Switch, Some(trans_get_discr(bcx, t, scrutinee, None, range_assert)))
-        }
-        layout::Univariant { .. } | layout::UntaggedUnion { .. } => {
-            // N.B.: Univariant means <= 1 enum variants (*not* == 1 variants).
-            (BranchKind::Single, None)
-        },
-        _ => bug!("{} is not an enum.", t)
-    }
-}
-
 pub fn is_discr_signed<'tcx>(l: &layout::Layout) -> bool {
     match *l {
         layout::CEnum { signed, .. }=> signed,
diff --git a/src/librustc_trans/glue.rs b/src/librustc_trans/glue.rs
index f25864c8f28..0c21573b9c4 100644
--- a/src/librustc_trans/glue.rs
+++ b/src/librustc_trans/glue.rs
@@ -20,7 +20,7 @@ use llvm::{ValueRef, get_param};
 use middle::lang_items::BoxFreeFnLangItem;
 use rustc::ty::subst::{Substs};
 use rustc::traits;
-use rustc::ty::{self, AdtDef, AdtKind, Ty, TypeFoldable};
+use rustc::ty::{self, layout, AdtDef, AdtKind, Ty, TypeFoldable};
 use rustc::ty::subst::Kind;
 use rustc::mir::tcx::LvalueTy;
 use mir::lvalue::LvalueRef;
@@ -471,14 +471,22 @@ fn drop_structural_ty<'a, 'tcx>(cx: Builder<'a, 'tcx>, ptr: LvalueRef<'tcx>) ->
                 // NB: we must hit the discriminant first so that structural
                 // comparison know not to proceed when the discriminants differ.
 
-                match adt::trans_switch(&cx, t, ptr.llval, false) {
-                    (adt::BranchKind::Single, None) => {
+                // Obtain a representation of the discriminant sufficient to translate
+                // destructuring; this may or may not involve the actual discriminant.
+                let l = cx.ccx.layout_of(t);
+                match *l {
+                    layout::Univariant { .. } |
+                    layout::UntaggedUnion { .. } => {
                         if n_variants != 0 {
                             assert!(n_variants == 1);
                             iter_variant(&cx, ptr, &adt, 0, substs);
                         }
                     }
-                    (adt::BranchKind::Switch, Some(lldiscrim_a)) => {
+                    layout::CEnum { .. } |
+                    layout::General { .. } |
+                    layout::RawNullablePointer { .. } |
+                    layout::StructWrappedNullablePointer { .. } => {
+                        let lldiscrim_a = adt::trans_get_discr(&cx, t, ptr.llval, None, false);
                         let tcx = cx.tcx();
                         drop_ty(&cx, LvalueRef::new_sized_ty(lldiscrim_a, tcx.types.isize));
 
@@ -511,7 +519,7 @@ fn drop_structural_ty<'a, 'tcx>(cx: Builder<'a, 'tcx>, ptr: LvalueRef<'tcx>) ->
                         }
                         cx = next_cx;
                     }
-                    _ => cx.sess().unimpl("value from adt::trans_switch in drop_structural_ty"),
+                    _ => bug!("{} is not an enum.", t),
                 }
             }
         },