493 lines
16 KiB
Rust
493 lines
16 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use metadata::csearch;
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use middle::astencode;
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use middle::ty;
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use middle;
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use syntax::{ast, ast_map, ast_util, visit};
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use syntax::ast::*;
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use core::hashmap::{HashMap, HashSet};
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//
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// This pass classifies expressions by their constant-ness.
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//
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// Constant-ness comes in 3 flavours:
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//
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// - Integer-constants: can be evaluated by the frontend all the way down
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// to their actual value. They are used in a few places (enum
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// discriminants, switch arms) and are a subset of
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// general-constants. They cover all the integer and integer-ish
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// literals (nil, bool, int, uint, char, iNN, uNN) and all integer
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// operators and copies applied to them.
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//
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// - General-constants: can be evaluated by LLVM but not necessarily by
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// the frontend; usually due to reliance on target-specific stuff such
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// as "where in memory the value goes" or "what floating point mode the
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// target uses". This _includes_ integer-constants, plus the following
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// constructors:
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//
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// fixed-size vectors and strings: [] and ""/_
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// vector and string slices: &[] and &""
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// tuples: (,)
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// records: {...}
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// enums: foo(...)
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// floating point literals and operators
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// & and * pointers
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// copies of general constants
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//
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// (in theory, probably not at first: if/match on integer-const
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// conditions / descriminants)
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//
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// - Non-constants: everything else.
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//
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pub enum constness {
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integral_const,
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general_const,
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non_const
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}
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pub fn join(a: constness, b: constness) -> constness {
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match (a, b) {
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(integral_const, integral_const) => integral_const,
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(integral_const, general_const)
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| (general_const, integral_const)
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| (general_const, general_const) => general_const,
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_ => non_const
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}
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}
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pub fn join_all(cs: &[constness]) -> constness {
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vec::foldl(integral_const, cs, |a, b| join(a, *b))
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}
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pub fn classify(e: @expr,
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tcx: ty::ctxt)
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-> constness {
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let did = ast_util::local_def(e.id);
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match tcx.ccache.find(&did) {
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Some(&x) => x,
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None => {
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let cn =
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match e.node {
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ast::expr_lit(lit) => {
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match lit.node {
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ast::lit_str(*) |
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ast::lit_float(*) => general_const,
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_ => integral_const
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}
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}
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ast::expr_copy(inner) |
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ast::expr_unary(_, inner) |
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ast::expr_paren(inner) => {
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classify(inner, tcx)
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}
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ast::expr_binary(_, a, b) => {
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join(classify(a, tcx),
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classify(b, tcx))
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}
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ast::expr_tup(ref es) |
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ast::expr_vec(ref es, ast::m_imm) => {
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join_all(vec::map(*es, |e| classify(*e, tcx)))
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}
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ast::expr_vstore(e, vstore) => {
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match vstore {
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ast::expr_vstore_slice => classify(e, tcx),
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ast::expr_vstore_uniq |
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ast::expr_vstore_box |
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ast::expr_vstore_mut_box |
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ast::expr_vstore_mut_slice => non_const
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}
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}
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ast::expr_struct(_, ref fs, None) => {
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let cs = do vec::map((*fs)) |f| {
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if f.node.mutbl == ast::m_imm {
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classify(f.node.expr, tcx)
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} else {
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non_const
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}
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};
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join_all(cs)
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}
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ast::expr_cast(base, _) => {
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let ty = ty::expr_ty(tcx, e);
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let base = classify(base, tcx);
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if ty::type_is_integral(ty) {
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join(integral_const, base)
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} else if ty::type_is_fp(ty) {
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join(general_const, base)
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} else {
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non_const
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}
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}
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ast::expr_field(base, _, _) => {
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classify(base, tcx)
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}
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ast::expr_index(base, idx) => {
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join(classify(base, tcx),
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classify(idx, tcx))
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}
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ast::expr_addr_of(ast::m_imm, base) => {
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classify(base, tcx)
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}
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// FIXME: (#3728) we can probably do something CCI-ish
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// surrounding nonlocal constants. But we don't yet.
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ast::expr_path(_) => {
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lookup_constness(tcx, e)
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}
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_ => non_const
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};
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tcx.ccache.insert(did, cn);
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cn
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}
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}
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}
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pub fn lookup_const(tcx: ty::ctxt, e: @expr) -> Option<@expr> {
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match tcx.def_map.find(&e.id) {
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Some(&ast::def_const(def_id)) => lookup_const_by_id(tcx, def_id),
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_ => None
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}
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}
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pub fn lookup_const_by_id(tcx: ty::ctxt,
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def_id: ast::def_id)
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-> Option<@expr> {
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if ast_util::is_local(def_id) {
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match tcx.items.find(&def_id.node) {
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None => None,
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Some(&ast_map::node_item(it, _)) => match it.node {
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item_const(_, const_expr) => Some(const_expr),
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_ => None
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},
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Some(_) => None
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}
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} else {
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let maps = astencode::Maps {
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root_map: @mut HashMap::new(),
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method_map: @mut HashMap::new(),
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vtable_map: @mut HashMap::new(),
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write_guard_map: @mut HashSet::new(),
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moves_map: @mut HashSet::new(),
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capture_map: @mut HashMap::new()
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};
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match csearch::maybe_get_item_ast(tcx, def_id,
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|a, b, c, d| astencode::decode_inlined_item(a, b, maps, /*bar*/ copy c, d)) {
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csearch::found(ast::ii_item(item)) => match item.node {
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item_const(_, const_expr) => Some(const_expr),
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_ => None
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},
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_ => None
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}
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}
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}
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pub fn lookup_constness(tcx: ty::ctxt, e: @expr) -> constness {
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match lookup_const(tcx, e) {
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Some(rhs) => {
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let ty = ty::expr_ty(tcx, rhs);
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if ty::type_is_integral(ty) {
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integral_const
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} else {
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general_const
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}
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}
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None => non_const
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}
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}
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pub fn process_crate(crate: @ast::crate,
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tcx: ty::ctxt) {
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let v = visit::mk_simple_visitor(@visit::SimpleVisitor {
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visit_expr_post: |e| { classify(e, tcx); },
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.. *visit::default_simple_visitor()
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});
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visit::visit_crate(crate, (), v);
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tcx.sess.abort_if_errors();
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}
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// FIXME (#33): this doesn't handle big integer/float literals correctly
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// (nor does the rest of our literal handling).
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#[deriving(Eq)]
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pub enum const_val {
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const_float(f64),
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const_int(i64),
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const_uint(u64),
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const_str(~str),
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const_bool(bool)
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}
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pub fn eval_const_expr(tcx: middle::ty::ctxt, e: @expr) -> const_val {
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match eval_const_expr_partial(tcx, e) {
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Ok(ref r) => (/*bad*/copy *r),
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Err(ref s) => fail!(/*bad*/copy *s)
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}
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}
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pub fn eval_const_expr_partial(tcx: middle::ty::ctxt, e: @expr)
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-> Result<const_val, ~str> {
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use middle::ty;
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fn fromb(b: bool) -> Result<const_val, ~str> { Ok(const_int(b as i64)) }
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match e.node {
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expr_unary(neg, inner) => {
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match eval_const_expr_partial(tcx, inner) {
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Ok(const_float(f)) => Ok(const_float(-f)),
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Ok(const_int(i)) => Ok(const_int(-i)),
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Ok(const_uint(i)) => Ok(const_uint(-i)),
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Ok(const_str(_)) => Err(~"Negate on string"),
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Ok(const_bool(_)) => Err(~"Negate on boolean"),
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ref err => (/*bad*/copy *err)
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}
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}
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expr_unary(not, inner) => {
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match eval_const_expr_partial(tcx, inner) {
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Ok(const_int(i)) => Ok(const_int(!i)),
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Ok(const_uint(i)) => Ok(const_uint(!i)),
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Ok(const_bool(b)) => Ok(const_bool(!b)),
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_ => Err(~"Not on float or string")
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}
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}
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expr_binary(op, a, b) => {
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match (eval_const_expr_partial(tcx, a),
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eval_const_expr_partial(tcx, b)) {
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(Ok(const_float(a)), Ok(const_float(b))) => {
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match op {
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add => Ok(const_float(a + b)),
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subtract => Ok(const_float(a - b)),
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mul => Ok(const_float(a * b)),
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div => Ok(const_float(a / b)),
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rem => Ok(const_float(a % b)),
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eq => fromb(a == b),
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lt => fromb(a < b),
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le => fromb(a <= b),
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ne => fromb(a != b),
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ge => fromb(a >= b),
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gt => fromb(a > b),
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_ => Err(~"Can't do this op on floats")
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}
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}
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(Ok(const_int(a)), Ok(const_int(b))) => {
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match op {
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add => Ok(const_int(a + b)),
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subtract => Ok(const_int(a - b)),
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mul => Ok(const_int(a * b)),
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div if b == 0 => Err(~"attempted to divide by zero"),
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div => Ok(const_int(a / b)),
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rem if b == 0 => Err(~"attempted remainder with a divisor of zero"),
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rem => Ok(const_int(a % b)),
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and | bitand => Ok(const_int(a & b)),
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or | bitor => Ok(const_int(a | b)),
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bitxor => Ok(const_int(a ^ b)),
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shl => Ok(const_int(a << b)),
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shr => Ok(const_int(a >> b)),
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eq => fromb(a == b),
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lt => fromb(a < b),
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le => fromb(a <= b),
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ne => fromb(a != b),
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ge => fromb(a >= b),
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gt => fromb(a > b)
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}
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}
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(Ok(const_uint(a)), Ok(const_uint(b))) => {
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match op {
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add => Ok(const_uint(a + b)),
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subtract => Ok(const_uint(a - b)),
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mul => Ok(const_uint(a * b)),
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div if b == 0 => Err(~"attempted to divide by zero"),
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div => Ok(const_uint(a / b)),
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rem if b == 0 => Err(~"attempted remainder with a divisor of zero"),
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rem => Ok(const_uint(a % b)),
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and | bitand => Ok(const_uint(a & b)),
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or | bitor => Ok(const_uint(a | b)),
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bitxor => Ok(const_uint(a ^ b)),
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shl => Ok(const_uint(a << b)),
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shr => Ok(const_uint(a >> b)),
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eq => fromb(a == b),
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lt => fromb(a < b),
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le => fromb(a <= b),
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ne => fromb(a != b),
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ge => fromb(a >= b),
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gt => fromb(a > b),
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}
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}
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// shifts can have any integral type as their rhs
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(Ok(const_int(a)), Ok(const_uint(b))) => {
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match op {
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shl => Ok(const_int(a << b)),
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shr => Ok(const_int(a >> b)),
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_ => Err(~"Can't do this op on an int and uint")
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}
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}
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(Ok(const_uint(a)), Ok(const_int(b))) => {
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match op {
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shl => Ok(const_uint(a << b)),
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shr => Ok(const_uint(a >> b)),
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_ => Err(~"Can't do this op on a uint and int")
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}
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}
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(Ok(const_bool(a)), Ok(const_bool(b))) => {
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Ok(const_bool(match op {
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and => a && b,
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or => a || b,
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bitxor => a ^ b,
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bitand => a & b,
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bitor => a | b,
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eq => a == b,
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ne => a != b,
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_ => return Err(~"Can't do this op on bools")
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}))
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}
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_ => Err(~"Bad operands for binary")
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}
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}
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expr_cast(base, _) => {
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let ety = ty::expr_ty(tcx, e);
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let base = eval_const_expr_partial(tcx, base);
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match /*bad*/copy base {
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Err(_) => base,
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Ok(val) => {
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match ty::get(ety).sty {
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ty::ty_float(_) => match val {
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const_uint(u) => Ok(const_float(u as f64)),
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const_int(i) => Ok(const_float(i as f64)),
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const_float(_) => base,
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_ => Err(~"Can't cast float to str"),
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},
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ty::ty_uint(_) => match val {
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const_uint(_) => base,
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const_int(i) => Ok(const_uint(i as u64)),
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const_float(f) => Ok(const_uint(f as u64)),
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_ => Err(~"Can't cast str to uint"),
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},
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ty::ty_int(_) | ty::ty_bool => match val {
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const_uint(u) => Ok(const_int(u as i64)),
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const_int(_) => base,
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const_float(f) => Ok(const_int(f as i64)),
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_ => Err(~"Can't cast str to int"),
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},
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_ => Err(~"Can't cast this type")
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}
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}
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}
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}
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expr_path(_) => {
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match lookup_const(tcx, e) {
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Some(actual_e) => eval_const_expr_partial(tcx, actual_e),
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None => Err(~"Non-constant path in constant expr")
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}
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}
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expr_lit(lit) => Ok(lit_to_const(lit)),
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// If we have a vstore, just keep going; it has to be a string
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expr_vstore(e, _) => eval_const_expr_partial(tcx, e),
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expr_paren(e) => eval_const_expr_partial(tcx, e),
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_ => Err(~"Unsupported constant expr")
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}
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}
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pub fn lit_to_const(lit: @lit) -> const_val {
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match lit.node {
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lit_str(s) => const_str(/*bad*/copy *s),
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lit_int(n, _) => const_int(n),
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lit_uint(n, _) => const_uint(n),
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lit_int_unsuffixed(n) => const_int(n),
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lit_float(n, _) => const_float(float::from_str(*n).get() as f64),
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lit_float_unsuffixed(n) =>
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const_float(float::from_str(*n).get() as f64),
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lit_nil => const_int(0i64),
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lit_bool(b) => const_bool(b)
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}
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}
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pub fn compare_const_vals(a: &const_val, b: &const_val) -> Option<int> {
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match (a, b) {
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(&const_int(a), &const_int(b)) => {
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if a == b {
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Some(0)
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} else if a < b {
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Some(-1)
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} else {
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Some(1)
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}
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}
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(&const_uint(a), &const_uint(b)) => {
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if a == b {
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Some(0)
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} else if a < b {
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Some(-1)
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} else {
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Some(1)
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}
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}
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(&const_float(a), &const_float(b)) => {
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if a == b {
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Some(0)
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} else if a < b {
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Some(-1)
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} else {
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Some(1)
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}
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}
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(&const_str(ref a), &const_str(ref b)) => {
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if (*a) == (*b) {
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Some(0)
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} else if (*a) < (*b) {
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Some(-1)
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} else {
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Some(1)
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}
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}
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(&const_bool(a), &const_bool(b)) => {
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if a == b {
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Some(0)
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} else if a < b {
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Some(-1)
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} else {
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Some(1)
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}
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}
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_ => {
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None
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}
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}
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}
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pub fn compare_lit_exprs(tcx: middle::ty::ctxt, a: @expr, b: @expr) -> Option<int> {
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compare_const_vals(&eval_const_expr(tcx, a), &eval_const_expr(tcx, b))
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}
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pub fn lit_expr_eq(tcx: middle::ty::ctxt, a: @expr, b: @expr) -> Option<bool> {
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match compare_lit_exprs(tcx, a, b) {
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Some(val) => Some(val == 0),
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None => None,
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}
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}
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pub fn lit_eq(a: @lit, b: @lit) -> Option<bool> {
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match compare_const_vals(&lit_to_const(a), &lit_to_const(b)) {
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Some(val) => Some(val == 0),
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None => None,
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}
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}
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