[MIR] use mir::repr::Constant in ExprKind::Repeat, close #29789

Author: fhahn

src/librustc_mir/build/expr/as_rvalue.rs

@@ -44,7 +44,6 @@ impl<'a,'tcx> Builder<'a,'tcx> {
             }
             ExprKind::Repeat { value, count } => {
                 let value_operand = unpack!(block = this.as_operand(block, value));
-                let count = this.as_constant(count);
                 block.and(Rvalue::Repeat(value_operand, count))
             }
             ExprKind::Borrow { region, borrow_kind, arg } => {

src/librustc_mir/hair/cx/expr.rs

@@ -325,14 +325,11 @@ impl<'tcx> Mirror<'tcx> for &'tcx hir::Expr {
 
             hir::ExprRepeat(ref v, ref c) => ExprKind::Repeat {
                 value: v.to_ref(),
-                count: Expr {
+                count: Constant {
                     ty: cx.tcx.expr_ty(c),
-                    temp_lifetime: None,
                     span: c.span,
-                    kind: ExprKind::Literal {
-                        literal: cx.const_eval_literal(c)
-                    }
-                }.to_ref()
+                    literal: cx.const_eval_literal(c)
+                }
             },
             hir::ExprRet(ref v) =>
                 ExprKind::Return { value: v.to_ref() },

src/librustc_mir/hair/mod.rs

@@ -14,7 +14,7 @@
 //! unit-tested and separated from the Rust source and compiler data
 //! structures.
 
-use rustc::mir::repr::{BinOp, BorrowKind, Field, Literal, Mutability, UnOp, ItemKind};
+use rustc::mir::repr::{Constant, BinOp, BorrowKind, Field, Literal, Mutability, UnOp, ItemKind};
 use rustc::middle::const_eval::ConstVal;
 use rustc::middle::def_id::DefId;
 use rustc::middle::region::CodeExtent;
@@ -213,10 +213,7 @@ pub enum ExprKind<'tcx> {
     },
     Repeat {
         value: ExprRef<'tcx>,
-        // FIXME(#29789): Add a separate hair::Constant<'tcx> so this could be more explicit about
-        // its contained data. Currently this should only contain expression of ExprKind::Literal
-        // kind.
-        count: ExprRef<'tcx>,
+        count: Constant<'tcx>,
     },
     Vec {
         fields: Vec<ExprRef<'tcx>>,
@@ -341,7 +338,6 @@ pub struct FieldPattern<'tcx> {
     pub field: Field,
     pub pattern: Pattern<'tcx>,
 }
-
 ///////////////////////////////////////////////////////////////////////////
 // The Mirror trait