1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 #![allow(non_camel_case_types)]
12 #![allow(unsigned_negation)]
14 pub use self::const_val::*;
15 pub use self::constness::*;
17 use metadata::csearch;
18 use middle::{astencode, def};
19 use middle::pat_util::def_to_path;
20 use middle::ty::{mod};
21 use middle::astconv_util::{ast_ty_to_prim_ty};
22 use util::nodemap::DefIdMap;
24 use syntax::ast::{mod, Expr};
25 use syntax::parse::token::InternedString;
27 use syntax::visit::{mod, Visitor};
28 use syntax::{ast_map, ast_util, codemap};
31 use std::collections::hash_map::Vacant;
34 // This pass classifies expressions by their constant-ness.
36 // Constant-ness comes in 3 flavours:
38 // - Integer-constants: can be evaluated by the frontend all the way down
39 // to their actual value. They are used in a few places (enum
40 // discriminants, switch arms) and are a subset of
41 // general-constants. They cover all the integer and integer-ish
42 // literals (nil, bool, int, uint, char, iNN, uNN) and all integer
43 // operators and copies applied to them.
45 // - General-constants: can be evaluated by LLVM but not necessarily by
46 // the frontend; usually due to reliance on target-specific stuff such
47 // as "where in memory the value goes" or "what floating point mode the
48 // target uses". This _includes_ integer-constants, plus the following
51 // fixed-size vectors and strings: [] and ""/_
52 // vector and string slices: &[] and &""
55 // floating point literals and operators
57 // copies of general constants
59 // (in theory, probably not at first: if/match on integer-const
60 // conditions / discriminants)
62 // - Non-constants: everything else.
71 impl Copy for constness {}
73 type constness_cache = DefIdMap<constness>;
75 pub fn join(a: constness, b: constness) -> constness {
77 (integral_const, integral_const) => integral_const,
78 (integral_const, general_const)
79 | (general_const, integral_const)
80 | (general_const, general_const) => general_const,
85 pub fn join_all<It: Iterator<constness>>(cs: It) -> constness {
86 cs.fold(integral_const, |a, b| join(a, b))
89 fn lookup_const<'a>(tcx: &'a ty::ctxt, e: &Expr) -> Option<&'a Expr> {
90 let opt_def = tcx.def_map.borrow().get(&e.id).cloned();
92 Some(def::DefConst(def_id)) => {
93 lookup_const_by_id(tcx, def_id)
95 Some(def::DefVariant(enum_def, variant_def, _)) => {
96 lookup_variant_by_id(tcx, enum_def, variant_def)
102 fn lookup_variant_by_id<'a>(tcx: &'a ty::ctxt,
103 enum_def: ast::DefId,
104 variant_def: ast::DefId)
105 -> Option<&'a Expr> {
106 fn variant_expr<'a>(variants: &'a [P<ast::Variant>], id: ast::NodeId)
107 -> Option<&'a Expr> {
108 for variant in variants.iter() {
109 if variant.node.id == id {
110 return variant.node.disr_expr.as_ref().map(|e| &**e);
116 if ast_util::is_local(enum_def) {
117 match tcx.map.find(enum_def.node) {
119 Some(ast_map::NodeItem(it)) => match it.node {
120 ast::ItemEnum(ast::EnumDef { ref variants }, _) => {
121 variant_expr(variants.as_slice(), variant_def.node)
128 match tcx.extern_const_variants.borrow().get(&variant_def) {
129 Some(&ast::DUMMY_NODE_ID) => return None,
131 return Some(tcx.map.expect_expr(expr_id));
135 let expr_id = match csearch::maybe_get_item_ast(tcx, enum_def,
136 |a, b, c, d| astencode::decode_inlined_item(a, b, c, d)) {
137 csearch::found(&ast::IIItem(ref item)) => match item.node {
138 ast::ItemEnum(ast::EnumDef { ref variants }, _) => {
139 // NOTE this doesn't do the right thing, it compares inlined
140 // NodeId's to the original variant_def's NodeId, but they
141 // come from different crates, so they will likely never match.
142 variant_expr(variants.as_slice(), variant_def.node).map(|e| e.id)
148 tcx.extern_const_variants.borrow_mut().insert(variant_def,
149 expr_id.unwrap_or(ast::DUMMY_NODE_ID));
150 expr_id.map(|id| tcx.map.expect_expr(id))
154 pub fn lookup_const_by_id<'a>(tcx: &'a ty::ctxt, def_id: ast::DefId)
155 -> Option<&'a Expr> {
156 if ast_util::is_local(def_id) {
157 match tcx.map.find(def_id.node) {
159 Some(ast_map::NodeItem(it)) => match it.node {
160 ast::ItemConst(_, ref const_expr) => {
168 match tcx.extern_const_statics.borrow().get(&def_id) {
169 Some(&ast::DUMMY_NODE_ID) => return None,
171 return Some(tcx.map.expect_expr(expr_id));
175 let expr_id = match csearch::maybe_get_item_ast(tcx, def_id,
176 |a, b, c, d| astencode::decode_inlined_item(a, b, c, d)) {
177 csearch::found(&ast::IIItem(ref item)) => match item.node {
178 ast::ItemConst(_, ref const_expr) => Some(const_expr.id),
183 tcx.extern_const_statics.borrow_mut().insert(def_id,
184 expr_id.unwrap_or(ast::DUMMY_NODE_ID));
185 expr_id.map(|id| tcx.map.expect_expr(id))
189 struct ConstEvalVisitor<'a, 'tcx: 'a> {
190 tcx: &'a ty::ctxt<'tcx>,
191 ccache: constness_cache,
194 impl<'a, 'tcx> ConstEvalVisitor<'a, 'tcx> {
195 fn classify(&mut self, e: &Expr) -> constness {
196 let did = ast_util::local_def(e.id);
197 match self.ccache.get(&did) {
198 Some(&x) => return x,
201 let cn = match e.node {
202 ast::ExprLit(ref lit) => {
204 ast::LitStr(..) | ast::LitFloat(..) => general_const,
209 ast::ExprUnary(_, ref inner) | ast::ExprParen(ref inner) =>
210 self.classify(&**inner),
212 ast::ExprBinary(_, ref a, ref b) =>
213 join(self.classify(&**a), self.classify(&**b)),
215 ast::ExprTup(ref es) |
216 ast::ExprVec(ref es) =>
217 join_all(es.iter().map(|e| self.classify(&**e))),
219 ast::ExprStruct(_, ref fs, None) => {
220 let cs = fs.iter().map(|f| self.classify(&*f.expr));
224 ast::ExprCast(ref base, _) => {
225 let ty = ty::expr_ty(self.tcx, e);
226 let base = self.classify(&**base);
227 if ty::type_is_integral(ty) {
228 join(integral_const, base)
229 } else if ty::type_is_fp(ty) {
230 join(general_const, base)
236 ast::ExprField(ref base, _) => self.classify(&**base),
238 ast::ExprTupField(ref base, _) => self.classify(&**base),
240 ast::ExprIndex(ref base, ref idx) =>
241 join(self.classify(&**base), self.classify(&**idx)),
243 ast::ExprAddrOf(ast::MutImmutable, ref base) =>
244 self.classify(&**base),
246 // FIXME: (#3728) we can probably do something CCI-ish
247 // surrounding nonlocal constants. But we don't yet.
248 ast::ExprPath(_) => self.lookup_constness(e),
250 ast::ExprRepeat(..) => general_const,
252 ast::ExprBlock(ref block) => {
254 Some(ref e) => self.classify(&**e),
255 None => integral_const
261 self.ccache.insert(did, cn);
265 fn lookup_constness(&self, e: &Expr) -> constness {
266 match lookup_const(self.tcx, e) {
268 let ty = ty::expr_ty(self.tcx, &*rhs);
269 if ty::type_is_integral(ty) {
281 impl<'a, 'tcx, 'v> Visitor<'v> for ConstEvalVisitor<'a, 'tcx> {
282 fn visit_expr_post(&mut self, e: &Expr) {
287 pub fn process_crate(tcx: &ty::ctxt) {
288 visit::walk_crate(&mut ConstEvalVisitor {
290 ccache: DefIdMap::new(),
292 tcx.sess.abort_if_errors();
296 // FIXME (#33): this doesn't handle big integer/float literals correctly
297 // (nor does the rest of our literal handling).
298 #[deriving(Clone, PartialEq)]
303 const_str(InternedString),
304 const_binary(Rc<Vec<u8> >),
308 pub fn const_expr_to_pat(tcx: &ty::ctxt, expr: &Expr) -> P<ast::Pat> {
309 let pat = match expr.node {
310 ast::ExprTup(ref exprs) =>
311 ast::PatTup(exprs.iter().map(|expr| const_expr_to_pat(tcx, &**expr)).collect()),
313 ast::ExprCall(ref callee, ref args) => {
314 let def = tcx.def_map.borrow()[callee.id].clone();
315 if let Vacant(entry) = tcx.def_map.borrow_mut().entry(expr.id) {
318 let path = match def {
319 def::DefStruct(def_id) => def_to_path(tcx, def_id),
320 def::DefVariant(_, variant_did, _) => def_to_path(tcx, variant_did),
323 let pats = args.iter().map(|expr| const_expr_to_pat(tcx, &**expr)).collect();
324 ast::PatEnum(path, Some(pats))
327 ast::ExprStruct(ref path, ref fields, None) => {
328 let field_pats = fields.iter().map(|field| codemap::Spanned {
329 span: codemap::DUMMY_SP,
330 node: ast::FieldPat {
331 ident: field.ident.node,
332 pat: const_expr_to_pat(tcx, &*field.expr),
336 ast::PatStruct(path.clone(), field_pats, false)
339 ast::ExprVec(ref exprs) => {
340 let pats = exprs.iter().map(|expr| const_expr_to_pat(tcx, &**expr)).collect();
341 ast::PatVec(pats, None, vec![])
344 ast::ExprPath(ref path) => {
345 let opt_def = tcx.def_map.borrow().get(&expr.id).cloned();
347 Some(def::DefStruct(..)) =>
348 ast::PatStruct(path.clone(), vec![], false),
349 Some(def::DefVariant(..)) =>
350 ast::PatEnum(path.clone(), None),
352 match lookup_const(tcx, expr) {
353 Some(actual) => return const_expr_to_pat(tcx, actual),
360 _ => ast::PatLit(P(expr.clone()))
362 P(ast::Pat { id: expr.id, node: pat, span: expr.span })
365 pub fn eval_const_expr(tcx: &ty::ctxt, e: &Expr) -> const_val {
366 match eval_const_expr_partial(tcx, e) {
368 Err(s) => tcx.sess.span_fatal(e.span, s.as_slice())
372 pub fn eval_const_expr_partial(tcx: &ty::ctxt, e: &Expr) -> Result<const_val, String> {
373 fn fromb(b: bool) -> Result<const_val, String> { Ok(const_int(b as i64)) }
375 ast::ExprUnary(ast::UnNeg, ref inner) => {
376 match eval_const_expr_partial(tcx, &**inner) {
377 Ok(const_float(f)) => Ok(const_float(-f)),
378 Ok(const_int(i)) => Ok(const_int(-i)),
379 Ok(const_uint(i)) => Ok(const_uint(-i)),
380 Ok(const_str(_)) => Err("negate on string".to_string()),
381 Ok(const_bool(_)) => Err("negate on boolean".to_string()),
382 ref err => ((*err).clone())
385 ast::ExprUnary(ast::UnNot, ref inner) => {
386 match eval_const_expr_partial(tcx, &**inner) {
387 Ok(const_int(i)) => Ok(const_int(!i)),
388 Ok(const_uint(i)) => Ok(const_uint(!i)),
389 Ok(const_bool(b)) => Ok(const_bool(!b)),
390 _ => Err("not on float or string".to_string())
393 ast::ExprBinary(op, ref a, ref b) => {
394 match (eval_const_expr_partial(tcx, &**a),
395 eval_const_expr_partial(tcx, &**b)) {
396 (Ok(const_float(a)), Ok(const_float(b))) => {
398 ast::BiAdd => Ok(const_float(a + b)),
399 ast::BiSub => Ok(const_float(a - b)),
400 ast::BiMul => Ok(const_float(a * b)),
401 ast::BiDiv => Ok(const_float(a / b)),
402 ast::BiRem => Ok(const_float(a % b)),
403 ast::BiEq => fromb(a == b),
404 ast::BiLt => fromb(a < b),
405 ast::BiLe => fromb(a <= b),
406 ast::BiNe => fromb(a != b),
407 ast::BiGe => fromb(a >= b),
408 ast::BiGt => fromb(a > b),
409 _ => Err("can't do this op on floats".to_string())
412 (Ok(const_int(a)), Ok(const_int(b))) => {
414 ast::BiAdd => Ok(const_int(a + b)),
415 ast::BiSub => Ok(const_int(a - b)),
416 ast::BiMul => Ok(const_int(a * b)),
417 ast::BiDiv if b == 0 => {
418 Err("attempted to divide by zero".to_string())
420 ast::BiDiv => Ok(const_int(a / b)),
421 ast::BiRem if b == 0 => {
422 Err("attempted remainder with a divisor of \
425 ast::BiRem => Ok(const_int(a % b)),
426 ast::BiAnd | ast::BiBitAnd => Ok(const_int(a & b)),
427 ast::BiOr | ast::BiBitOr => Ok(const_int(a | b)),
428 ast::BiBitXor => Ok(const_int(a ^ b)),
429 ast::BiShl => Ok(const_int(a << b as uint)),
430 ast::BiShr => Ok(const_int(a >> b as uint)),
431 ast::BiEq => fromb(a == b),
432 ast::BiLt => fromb(a < b),
433 ast::BiLe => fromb(a <= b),
434 ast::BiNe => fromb(a != b),
435 ast::BiGe => fromb(a >= b),
436 ast::BiGt => fromb(a > b)
439 (Ok(const_uint(a)), Ok(const_uint(b))) => {
441 ast::BiAdd => Ok(const_uint(a + b)),
442 ast::BiSub => Ok(const_uint(a - b)),
443 ast::BiMul => Ok(const_uint(a * b)),
444 ast::BiDiv if b == 0 => {
445 Err("attempted to divide by zero".to_string())
447 ast::BiDiv => Ok(const_uint(a / b)),
448 ast::BiRem if b == 0 => {
449 Err("attempted remainder with a divisor of \
452 ast::BiRem => Ok(const_uint(a % b)),
453 ast::BiAnd | ast::BiBitAnd => Ok(const_uint(a & b)),
454 ast::BiOr | ast::BiBitOr => Ok(const_uint(a | b)),
455 ast::BiBitXor => Ok(const_uint(a ^ b)),
456 ast::BiShl => Ok(const_uint(a << b as uint)),
457 ast::BiShr => Ok(const_uint(a >> b as uint)),
458 ast::BiEq => fromb(a == b),
459 ast::BiLt => fromb(a < b),
460 ast::BiLe => fromb(a <= b),
461 ast::BiNe => fromb(a != b),
462 ast::BiGe => fromb(a >= b),
463 ast::BiGt => fromb(a > b),
466 // shifts can have any integral type as their rhs
467 (Ok(const_int(a)), Ok(const_uint(b))) => {
469 ast::BiShl => Ok(const_int(a << b as uint)),
470 ast::BiShr => Ok(const_int(a >> b as uint)),
471 _ => Err("can't do this op on an int and uint".to_string())
474 (Ok(const_uint(a)), Ok(const_int(b))) => {
476 ast::BiShl => Ok(const_uint(a << b as uint)),
477 ast::BiShr => Ok(const_uint(a >> b as uint)),
478 _ => Err("can't do this op on a uint and int".to_string())
481 (Ok(const_bool(a)), Ok(const_bool(b))) => {
482 Ok(const_bool(match op {
483 ast::BiAnd => a && b,
485 ast::BiBitXor => a ^ b,
486 ast::BiBitAnd => a & b,
487 ast::BiBitOr => a | b,
490 _ => return Err("can't do this op on bools".to_string())
493 _ => Err("bad operands for binary".to_string())
496 ast::ExprCast(ref base, ref target_ty) => {
497 // This tends to get called w/o the type actually having been
498 // populated in the ctxt, which was causing things to blow up
499 // (#5900). Fall back to doing a limited lookup to get past it.
500 let ety = ty::expr_ty_opt(tcx, e)
501 .or_else(|| ast_ty_to_prim_ty(tcx, &**target_ty))
503 tcx.sess.span_fatal(target_ty.span,
504 "target type not found for const cast")
507 macro_rules! define_casts(
514 }) => (match ety.sty {
517 const_bool(b) => Ok($const_type(b as $intermediate_ty as $target_ty)),
518 const_uint(u) => Ok($const_type(u as $intermediate_ty as $target_ty)),
519 const_int(i) => Ok($const_type(i as $intermediate_ty as $target_ty)),
520 const_float(f) => Ok($const_type(f as $intermediate_ty as $target_ty)),
522 "can't cast this type to ", stringify!($const_type)
526 _ => Err("can't cast this type".to_string())
530 eval_const_expr_partial(tcx, &**base)
531 .and_then(|val| define_casts!(val, {
532 ty::ty_int(ast::TyI) => (int, const_int, i64),
533 ty::ty_int(ast::TyI8) => (i8, const_int, i64),
534 ty::ty_int(ast::TyI16) => (i16, const_int, i64),
535 ty::ty_int(ast::TyI32) => (i32, const_int, i64),
536 ty::ty_int(ast::TyI64) => (i64, const_int, i64),
537 ty::ty_uint(ast::TyU) => (uint, const_uint, u64),
538 ty::ty_uint(ast::TyU8) => (u8, const_uint, u64),
539 ty::ty_uint(ast::TyU16) => (u16, const_uint, u64),
540 ty::ty_uint(ast::TyU32) => (u32, const_uint, u64),
541 ty::ty_uint(ast::TyU64) => (u64, const_uint, u64),
542 ty::ty_float(ast::TyF32) => (f32, const_float, f64),
543 ty::ty_float(ast::TyF64) => (f64, const_float, f64)
546 ast::ExprPath(_) => {
547 match lookup_const(tcx, e) {
548 Some(actual_e) => eval_const_expr_partial(tcx, &*actual_e),
549 None => Err("non-constant path in constant expr".to_string())
552 ast::ExprLit(ref lit) => Ok(lit_to_const(&**lit)),
553 ast::ExprParen(ref e) => eval_const_expr_partial(tcx, &**e),
554 ast::ExprBlock(ref block) => {
556 Some(ref expr) => eval_const_expr_partial(tcx, &**expr),
557 None => Ok(const_int(0i64))
560 ast::ExprTupField(ref base, index) => {
561 // Get the base tuple if it is constant
562 if let Some(&ast::ExprTup(ref fields)) = lookup_const(tcx, &**base).map(|s| &s.node) {
563 // Check that the given index is within bounds and evaluate its value
564 if fields.len() > index.node {
565 return eval_const_expr_partial(tcx, &*fields[index.node])
567 return Err("tuple index out of bounds".to_string())
571 Err("non-constant struct in constant expr".to_string())
573 ast::ExprField(ref base, field_name) => {
574 // Get the base expression if it is a struct and it is constant
575 if let Some(&ast::ExprStruct(_, ref fields, _)) = lookup_const(tcx, &**base)
577 // Check that the given field exists and evaluate it
578 if let Some(f) = fields.iter().find(|f|
579 f.ident.node.as_str() == field_name.node.as_str()) {
580 return eval_const_expr_partial(tcx, &*f.expr)
582 return Err("nonexistent struct field".to_string())
586 Err("non-constant struct in constant expr".to_string())
588 _ => Err("unsupported constant expr".to_string())
592 pub fn lit_to_const(lit: &ast::Lit) -> const_val {
594 ast::LitStr(ref s, _) => const_str((*s).clone()),
595 ast::LitBinary(ref data) => {
596 const_binary(Rc::new(data.iter().map(|x| *x).collect()))
598 ast::LitByte(n) => const_uint(n as u64),
599 ast::LitChar(n) => const_uint(n as u64),
600 ast::LitInt(n, ast::SignedIntLit(_, ast::Plus)) |
601 ast::LitInt(n, ast::UnsuffixedIntLit(ast::Plus)) => const_int(n as i64),
602 ast::LitInt(n, ast::SignedIntLit(_, ast::Minus)) |
603 ast::LitInt(n, ast::UnsuffixedIntLit(ast::Minus)) => const_int(-(n as i64)),
604 ast::LitInt(n, ast::UnsignedIntLit(_)) => const_uint(n),
605 ast::LitFloat(ref n, _) |
606 ast::LitFloatUnsuffixed(ref n) => {
607 const_float(from_str::<f64>(n.get()).unwrap() as f64)
609 ast::LitBool(b) => const_bool(b)
613 fn compare_vals<T: PartialOrd>(a: T, b: T) -> Option<int> {
614 Some(if a == b { 0 } else if a < b { -1 } else { 1 })
616 pub fn compare_const_vals(a: &const_val, b: &const_val) -> Option<int> {
618 (&const_int(a), &const_int(b)) => compare_vals(a, b),
619 (&const_uint(a), &const_uint(b)) => compare_vals(a, b),
620 (&const_float(a), &const_float(b)) => compare_vals(a, b),
621 (&const_str(ref a), &const_str(ref b)) => compare_vals(a, b),
622 (&const_bool(a), &const_bool(b)) => compare_vals(a, b),
623 (&const_binary(ref a), &const_binary(ref b)) => compare_vals(a, b),
628 pub fn compare_lit_exprs(tcx: &ty::ctxt, a: &Expr, b: &Expr) -> Option<int> {
629 compare_const_vals(&eval_const_expr(tcx, a), &eval_const_expr(tcx, b))