Pattern match over PlaceRef rather than Place

This prepares the code base for when projection is interned. Place's
projection field is going to be `&List<PlaceElem<'tcx>>` so we won't be
able to pattern match against it.

src/librustc/mir/mod.rs

@@ -1908,15 +1908,15 @@ impl<'tcx> Place<'tcx> {
     //
     // FIXME: can we safely swap the semantics of `fn base_local` below in here instead?
     pub fn local_or_deref_local(&self) -> Option<Local> {
-        match self {
-            Place {
-                base: PlaceBase::Local(local),
-                projection: box [],
+        match self.as_ref() {
+            PlaceRef {
+                base: &PlaceBase::Local(local),
+                projection: &[],
             } |
-            Place {
-                base: PlaceBase::Local(local),
-                projection: box [ProjectionElem::Deref],
-            } => Some(*local),
+            PlaceRef {
+                base: &PlaceBase::Local(local),
+                projection: &[ProjectionElem::Deref],
+            } => Some(local),
             _ => None,
         }
     }

src/librustc_codegen_ssa/mir/analyze.rs

@@ -191,10 +191,7 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
                     location: Location) {
         debug!("visit_assign(place={:?}, rvalue={:?})", place, rvalue);
 
-        if let mir::Place {
-            base: mir::PlaceBase::Local(index),
-            projection: box [],
-        } = *place {
+        if let Some(index) = place.as_local() {
             self.assign(index, location);
             let decl_span = self.fx.mir.local_decls[index].source_info.span;
             if !self.fx.rvalue_creates_operand(rvalue, decl_span) {

src/librustc_codegen_ssa/mir/block.rs

@@ -2,7 +2,7 @@ use rustc_index::vec::Idx;
 use rustc::middle::lang_items;
 use rustc::ty::{self, Ty, TypeFoldable, Instance};
 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, FnTypeExt};
-use rustc::mir::{self, Place, PlaceBase, Static, StaticKind};
+use rustc::mir::{self, PlaceBase, Static, StaticKind};
 use rustc::mir::interpret::PanicInfo;
 use rustc_target::abi::call::{ArgType, FnType, PassMode};
 use rustc_target::spec::abi::Abi;
@@ -630,53 +630,43 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 // checked by const-qualification, which also
                 // promotes any complex rvalues to constants.
                 if i == 2 && intrinsic.unwrap().starts_with("simd_shuffle") {
-                    match *arg {
+                    match arg {
                         // The shuffle array argument is usually not an explicit constant,
                         // but specified directly in the code. This means it gets promoted
                         // and we can then extract the value by evaluating the promoted.
-                        mir::Operand::Copy(
-                            Place {
-                                base: PlaceBase::Static(box Static {
-                                    kind: StaticKind::Promoted(promoted, _),
+                        mir::Operand::Copy(place) | mir::Operand::Move(place) => {
+                            if let mir::PlaceRef {
+                                base:
+                                    &PlaceBase::Static(box Static {
+                                        kind: StaticKind::Promoted(promoted, _),
+                                        ty,
+                                        def_id: _,
+                                    }),
+                                projection: &[],
+                            } = place.as_ref()
+                            {
+                                let param_env = ty::ParamEnv::reveal_all();
+                                let cid = mir::interpret::GlobalId {
+                                    instance: self.instance,
+                                    promoted: Some(promoted),
+                                };
+                                let c = bx.tcx().const_eval(param_env.and(cid));
+                                let (llval, ty) = self.simd_shuffle_indices(
+                                    &bx,
+                                    terminator.source_info.span,
                                     ty,
-                                    def_id: _,
-                                }),
-                                projection: box [],
+                                    c,
+                                );
+                                return OperandRef {
+                                    val: Immediate(llval),
+                                    layout: bx.layout_of(ty),
+                                };
+                            } else {
+                                span_bug!(span, "shuffle indices must be constant");
                             }
-                        ) |
-                        mir::Operand::Move(
-                            Place {
-                                base: PlaceBase::Static(box Static {
-                                    kind: StaticKind::Promoted(promoted, _),
-                                    ty,
-                                    def_id: _,
-                                }),
-                                projection: box [],
-                            }
-                        ) => {
-                            let param_env = ty::ParamEnv::reveal_all();
-                            let cid = mir::interpret::GlobalId {
-                                instance: self.instance,
-                                promoted: Some(promoted),
-                            };
-                            let c = bx.tcx().const_eval(param_env.and(cid));
-                            let (llval, ty) = self.simd_shuffle_indices(
-                                &bx,
-                                terminator.source_info.span,
-                                ty,
-                                c,
-                            );
-                            return OperandRef {
-                                val: Immediate(llval),
-                                layout: bx.layout_of(ty),
-                            };
-
-                        }
-                        mir::Operand::Copy(_) |
-                        mir::Operand::Move(_) => {
-                            span_bug!(span, "shuffle indices must be constant");
                         }
-                        mir::Operand::Constant(ref constant) => {
+
+                        mir::Operand::Constant(constant) => {
                             let c = self.eval_mir_constant(constant);
                             let (llval, ty) = self.simd_shuffle_indices(
                                 &bx,
@@ -1117,10 +1107,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         if fn_ret.is_ignore() {
             return ReturnDest::Nothing;
         }
-        let dest = if let mir::Place {
-            base: mir::PlaceBase::Local(index),
-            projection: box [],
-        } = *dest {
+        let dest = if let Some(index) = dest.as_local() {
             match self.locals[index] {
                 LocalRef::Place(dest) => dest,
                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
@@ -1178,10 +1165,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         src: &mir::Operand<'tcx>,
         dst: &mir::Place<'tcx>
     ) {
-        if let mir::Place {
-            base: mir::PlaceBase::Local(index),
-            projection: box [],
-        } = *dst {
+        if let Some(index) = dst.as_local() {
             match self.locals[index] {
                 LocalRef::Place(place) => self.codegen_transmute_into(bx, src, place),
                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),

src/librustc_codegen_ssa/mir/rvalue.rs

@@ -530,10 +530,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> Bx::Value {
         // ZST are passed as operands and require special handling
         // because codegen_place() panics if Local is operand.
-        if let mir::Place {
-            base: mir::PlaceBase::Local(index),
-            projection: box [],
-        } = *place {
+        if let Some(index) = place.as_local() {
             if let LocalRef::Operand(Some(op)) = self.locals[index] {
                 if let ty::Array(_, n) = op.layout.ty.kind {
                     let n = n.eval_usize(bx.cx().tcx(), ty::ParamEnv::reveal_all());

src/librustc_codegen_ssa/mir/statement.rs

@@ -17,11 +17,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.set_debug_loc(&mut bx, statement.source_info);
         match statement.kind {
             mir::StatementKind::Assign(box(ref place, ref rvalue)) => {
-                if let mir::Place {
-                    base: mir::PlaceBase::Local(index),
-                    projection: box [],
-                } = place {
-                    match self.locals[*index] {
+                if let Some(index) = place.as_local() {
+                    match self.locals[index] {
                         LocalRef::Place(cg_dest) => {
                             self.codegen_rvalue(bx, cg_dest, rvalue)
                         }
@@ -30,7 +27,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         }
                         LocalRef::Operand(None) => {
                             let (mut bx, operand) = self.codegen_rvalue_operand(bx, rvalue);
-                            if let Some(name) = self.mir.local_decls[*index].name {
+                            if let Some(name) = self.mir.local_decls[index].name {
                                 match operand.val {
                                     OperandValue::Ref(x, ..) |
                                     OperandValue::Immediate(x) => {
@@ -44,7 +41,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                     }
                                 }
                             }
-                            self.locals[*index] = LocalRef::Operand(Some(operand));
+                            self.locals[index] = LocalRef::Operand(Some(operand));
                             bx
                         }
                         LocalRef::Operand(Some(op)) => {

src/librustc_mir/borrow_check/borrow_set.rs

@@ -315,10 +315,7 @@ impl<'a, 'tcx> GatherBorrows<'a, 'tcx> {
         //    TEMP = &foo
         //
         // so extract `temp`.
-        let temp = if let &mir::Place {
-            base: mir::PlaceBase::Local(temp),
-            projection: box [],
-        } = assigned_place {
+        let temp = if let Some(temp) = assigned_place.as_local() {
             temp
         } else {
             span_bug!(