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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! See docs in build/expr/mod.rs
use build::Builder;
use hair::*;
use rustc::mir::*;
impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
/// Compile `expr`, yielding a compile-time constant. Assumes that
/// `expr` is a valid compile-time constant!
pub fn as_constant<M>(&mut self, expr: M) -> Constant<'tcx>
where M: Mirror<'tcx, Output=Expr<'tcx>>
{
let expr = self.hir.mirror(expr);
self.expr_as_constant(expr)
}
fn expr_as_constant(&mut self, expr: Expr<'tcx>) -> Constant<'tcx> {
let this = self;
let Expr { ty, temp_lifetime: _, span, kind }
= expr;
match kind {
ExprKind::Scope { region_scope: _, lint_level: _, value } =>
this.as_constant(value),
ExprKind::Literal { literal } =>
Constant { span: span, ty: ty, literal: literal },
_ =>
span_bug!(
span,
"expression is not a valid constant {:?}",
kind),
}
}
}
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