Rollup merge of rust-lang#40602 - oli-obk:fn_const, r=eddyb

Represent function pointers in mir-constants as a Value instead of Item

r? @eddyb

src/librustc_borrowck/borrowck/mir/elaborate_drops.rs

@@ -875,9 +875,8 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
                     func: Operand::Constant(Constant {
                         span: c.source_info.span,
                         ty: fty,
-                        literal: Literal::Item {
-                            def_id: free_func,
-                            substs: substs
+                        literal: Literal::Value {
+                            value: ConstVal::Function(free_func, substs),
                         }
                     }),
                     args: vec![Operand::Consume(c.lvalue.clone())],

src/librustc_mir/build/scope.rs

@@ -89,6 +89,7 @@ should go to.
 use build::{BlockAnd, BlockAndExtension, Builder, CFG};
 use rustc::middle::region::{CodeExtent, CodeExtentData};
 use rustc::middle::lang_items;
+use rustc::middle::const_val::ConstVal;
 use rustc::ty::subst::{Kind, Subst};
 use rustc::ty::{Ty, TyCtxt};
 use rustc::mir::*;
@@ -783,9 +784,8 @@ fn build_free<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
         func: Operand::Constant(Constant {
             span: data.span,
             ty: tcx.item_type(free_func).subst(tcx, substs),
-            literal: Literal::Item {
-                def_id: free_func,
-                substs: substs
+            literal: Literal::Value {
+                value: ConstVal::Function(free_func, substs),
             }
         }),
         args: vec![Operand::Consume(data.value.clone())],

src/librustc_mir/hair/cx/expr.rs

@@ -711,9 +711,8 @@ fn method_callee<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         ty: callee.ty,
         span: expr.span,
         kind: ExprKind::Literal {
-            literal: Literal::Item {
-                def_id: callee.def_id,
-                substs: callee.substs,
+            literal: Literal::Value {
+                value: ConstVal::Function(callee.def_id, callee.substs),
             },
         },
     }
@@ -740,22 +739,32 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                      -> ExprKind<'tcx> {
     let substs = cx.tables().node_id_item_substs(expr.id)
         .unwrap_or_else(|| cx.tcx.intern_substs(&[]));
-    let def_id = match def {
+    match def {
         // A regular function, constructor function or a constant.
         Def::Fn(def_id) |
         Def::Method(def_id) |
         Def::StructCtor(def_id, CtorKind::Fn) |
-        Def::VariantCtor(def_id, CtorKind::Fn) |
+        Def::VariantCtor(def_id, CtorKind::Fn) => ExprKind::Literal {
+            literal: Literal::Value {
+                value: ConstVal::Function(def_id, substs),
+            },
+        },
+
         Def::Const(def_id) |
-        Def::AssociatedConst(def_id) => def_id,
+        Def::AssociatedConst(def_id) => ExprKind::Literal {
+            literal: Literal::Item {
+                def_id: def_id,
+                substs: substs,
+            },
+        },
 
         Def::StructCtor(def_id, CtorKind::Const) |
         Def::VariantCtor(def_id, CtorKind::Const) => {
             match cx.tables().node_id_to_type(expr.id).sty {
                 // A unit struct/variant which is used as a value.
                 // We return a completely different ExprKind here to account for this special case.
                 ty::TyAdt(adt_def, substs) => {
-                    return ExprKind::Adt {
+                    ExprKind::Adt {
                         adt_def: adt_def,
                         variant_index: adt_def.variant_index_with_id(def_id),
                         substs: substs,
@@ -767,17 +776,11 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             }
         }
 
-        Def::Static(node_id, _) => return ExprKind::StaticRef { id: node_id },
+        Def::Static(node_id, _) => ExprKind::StaticRef { id: node_id },
 
-        Def::Local(..) | Def::Upvar(..) => return convert_var(cx, expr, def),
+        Def::Local(..) | Def::Upvar(..) => convert_var(cx, expr, def),
 
         _ => span_bug!(expr.span, "def `{:?}` not yet implemented", def),
-    };
-    ExprKind::Literal {
-        literal: Literal::Item {
-            def_id: def_id,
-            substs: substs,
-        },
     }
 }
 

src/librustc_mir/hair/cx/mod.rs

@@ -132,9 +132,8 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
                 let method_ty = self.tcx.item_type(item.def_id);
                 let method_ty = method_ty.subst(self.tcx, substs);
                 return (method_ty,
-                        Literal::Item {
-                            def_id: item.def_id,
-                            substs: substs,
+                        Literal::Value {
+                            value: ConstVal::Function(item.def_id, substs),
                         });
             }
         }

src/librustc_mir/transform/qualify_consts.rs

@@ -568,11 +568,6 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                 });
             }
             Operand::Constant(ref constant) => {
-                // Only functions and methods can have these types.
-                if let ty::TyFnDef(..) = constant.ty.sty {
-                    return;
-                }
-
                 if let Literal::Item { def_id, substs } = constant.literal {
                     // Don't peek inside generic (associated) constants.
                     if substs.types().next().is_some() {

src/librustc_mir/transform/type_check.rs

@@ -15,6 +15,7 @@ use rustc::infer::{self, InferCtxt, InferOk};
 use rustc::traits::{self, Reveal};
 use rustc::ty::fold::TypeFoldable;
 use rustc::ty::{self, Ty, TyCtxt, TypeVariants};
+use rustc::middle::const_val::ConstVal;
 use rustc::mir::*;
 use rustc::mir::tcx::LvalueTy;
 use rustc::mir::transform::{MirPass, MirSource, Pass};
@@ -526,7 +527,9 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
     fn is_box_free(&self, operand: &Operand<'tcx>) -> bool {
         match operand {
             &Operand::Constant(Constant {
-                literal: Literal::Item { def_id, .. }, ..
+                literal: Literal::Value {
+                    value: ConstVal::Function(def_id, _), ..
+                }, ..
             }) => {
                 Some(def_id) == self.tcx().lang_items.box_free_fn()
             }

src/librustc_trans/mir/analyze.rs

@@ -13,7 +13,8 @@
 
 use rustc_data_structures::bitvec::BitVector;
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
-use rustc::mir::{self, Location, TerminatorKind};
+use rustc::middle::const_val::ConstVal;
+use rustc::mir::{self, Location, TerminatorKind, Literal};
 use rustc::mir::visit::{Visitor, LvalueContext};
 use rustc::mir::traversal;
 use common;
@@ -109,7 +110,9 @@ impl<'mir, 'a, 'tcx> Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'tcx> {
         match *kind {
             mir::TerminatorKind::Call {
                 func: mir::Operand::Constant(mir::Constant {
-                    literal: mir::Literal::Item { def_id, .. }, ..
+                    literal: Literal::Value {
+                        value: ConstVal::Function(def_id, _), ..
+                    }, ..
                 }),
                 ref args, ..
             } if Some(def_id) == self.cx.ccx.tcx().lang_items.box_free_fn() => {

src/librustc_trans/mir/constant.rs

@@ -101,9 +101,12 @@ impl<'tcx> Const<'tcx> {
             ConstVal::Str(ref v) => C_str_slice(ccx, v.clone()),
             ConstVal::ByteStr(ref v) => consts::addr_of(ccx, C_bytes(ccx, v), 1, "byte_str"),
             ConstVal::Struct(_) | ConstVal::Tuple(_) |
-            ConstVal::Array(..) | ConstVal::Repeat(..) |
+            ConstVal::Array(..) | ConstVal::Repeat(..) => {
+                bug!("MIR must not use `{:?}` (aggregates are expanded to MIR rvalues)", cv)
+            }
             ConstVal::Function(..) => {
-                bug!("MIR must not use `{:?}` (which refers to a local ID)", cv)
+                let llty = type_of::type_of(ccx, ty);
+                return Const::new(C_null(llty), ty);
             }
             ConstVal::Char(c) => C_integral(Type::char(ccx), c as u64, false),
         };
@@ -477,13 +480,6 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                 let ty = self.monomorphize(&constant.ty);
                 match constant.literal.clone() {
                     mir::Literal::Item { def_id, substs } => {
-                        // Shortcut for zero-sized types, including function item
-                        // types, which would not work with MirConstContext.
-                        if common::type_is_zero_size(self.ccx, ty) {
-                            let llty = type_of::type_of(self.ccx, ty);
-                            return Ok(Const::new(C_null(llty), ty));
-                        }
-
                         let substs = self.monomorphize(&substs);
                         let instance = Instance::new(def_id, substs);
                         MirConstContext::trans_def(self.ccx, instance, IndexVec::new())
@@ -927,13 +923,6 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
         let ty = self.monomorphize(&constant.ty);
         let result = match constant.literal.clone() {
             mir::Literal::Item { def_id, substs } => {
-                // Shortcut for zero-sized types, including function item
-                // types, which would not work with MirConstContext.
-                if common::type_is_zero_size(bcx.ccx, ty) {
-                    let llty = type_of::type_of(bcx.ccx, ty);
-                    return Const::new(C_null(llty), ty);
-                }
-
                 let substs = self.monomorphize(&substs);
                 let instance = Instance::new(def_id, substs);
                 MirConstContext::trans_def(bcx.ccx, instance, IndexVec::new())