Simplify handling of dropping structs.

Author: Mark-Simulacrum

src/librustc_trans/common.rs

@@ -15,7 +15,6 @@
 use llvm;
 use llvm::{ValueRef, ContextRef, TypeKind};
 use llvm::{True, False, Bool, OperandBundleDef};
-use rustc::hir::def::Def;
 use rustc::hir::def_id::DefId;
 use rustc::hir::map::DefPathData;
 use rustc::util::common::MemoizationMap;
@@ -38,7 +37,7 @@ use std::borrow::Cow;
 use std::iter;
 
 use syntax::ast;
-use syntax::symbol::{Symbol, InternedString};
+use syntax::symbol::InternedString;
 use syntax_pos::Span;
 
 use rustc_i128::u128;
@@ -169,55 +168,6 @@ pub fn type_is_zero_size<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -
 *
 */
 
-use Disr;
-
-/// The concrete version of ty::FieldDef. The name is the field index if
-/// the field is numeric.
-pub struct Field<'tcx>(pub ast::Name, pub Ty<'tcx>);
-
-/// The concrete version of ty::VariantDef
-pub struct VariantInfo<'tcx> {
-    pub discr: Disr,
-    pub fields: Vec<Field<'tcx>>
-}
-
-impl<'a, 'tcx> VariantInfo<'tcx> {
-    pub fn from_ty(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                   ty: Ty<'tcx>,
-                   opt_def: Option<Def>)
-                   -> Self
-    {
-        match ty.sty {
-            ty::TyAdt(adt, substs) => {
-                let variant = match opt_def {
-                    None => adt.struct_variant(),
-                    Some(def) => adt.variant_of_def(def)
-                };
-
-                VariantInfo {
-                    discr: Disr::from(variant.disr_val),
-                    fields: variant.fields.iter().map(|f| {
-                        Field(f.name, monomorphize::field_ty(tcx, substs, f))
-                    }).collect()
-                }
-            }
-
-            ty::TyTuple(ref v) => {
-                VariantInfo {
-                    discr: Disr(0),
-                    fields: v.iter().enumerate().map(|(i, &t)| {
-                        Field(Symbol::intern(&i.to_string()), t)
-                    }).collect()
-                }
-            }
-
-            _ => {
-                bug!("cannot get field types from the type {:?}", ty);
-            }
-        }
-    }
-}
-
 /// A structure representing an active landing pad for the duration of a basic
 /// block.
 ///

src/librustc_trans/glue.rs

@@ -13,6 +13,7 @@
 // Code relating to drop glue.
 
 use std;
+use std::ptr;
 use std::iter;
 
 use llvm;
@@ -444,21 +445,15 @@ fn drop_structural_ty<'a, 'tcx>(
         }
         ty::TyAdt(adt, substs) => match adt.adt_kind() {
             AdtKind::Struct => {
-                let VariantInfo { fields, discr } = VariantInfo::from_ty(cx.tcx(), t, None);
-                for (i, &Field(_, field_ty)) in fields.iter().enumerate() {
-                    let mut ptr = ptr.clone();
-                    ptr.ty = LvalueTy::Downcast {
-                        adt_def: adt,
-                        substs: substs,
-                        variant_index: Disr::from(discr).0 as usize,
-                    };
-                    let llfld_a = ptr.trans_field_ptr(&cx, i);
-                    let ptr = if cx.ccx.shared().type_is_sized(field_ty) {
-                        LvalueRef::new_sized_ty(llfld_a, field_ty)
-                    } else {
-                        LvalueRef::new_unsized_ty(llfld_a, ptr.llextra, field_ty)
-                    };
-                    drop_ty(&cx, ptr);
+                for (i, field) in adt.variants[0].fields.iter().enumerate() {
+                    let field_ty = monomorphize::field_ty(cx.tcx(), substs, field);
+                    let mut field_ptr = ptr.clone();
+                    field_ptr.llval = ptr.trans_field_ptr(&cx, i);
+                    field_ptr.ty = LvalueTy::from_ty(field_ty);
+                    if cx.ccx.shared().type_is_sized(field_ty) {
+                        field_ptr.llextra = ptr::null_mut();
+                    }
+                    drop_ty(&cx, field_ptr);
                 }
             }
             AdtKind::Union => {