/
_match.rs
790 lines (729 loc) · 30 KB
/
_match.rs
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// Copyright 2012-2014 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.
#![allow(non_camel_case_types)]
use middle::def;
use middle::pat_util::{PatIdMap, pat_id_map, pat_is_binding, pat_is_const};
use middle::subst;
use middle::subst::Subst;
use middle::ty;
use middle::typeck::check::demand;
use middle::typeck::check::{check_expr, check_expr_has_type, FnCtxt};
use middle::typeck::check::{instantiate_path, lookup_def};
use middle::typeck::check::{structure_of, valid_range_bounds};
use middle::typeck::infer;
use middle::typeck::require_same_types;
use std::collections::{HashMap, HashSet};
use std::gc::Gc;
use syntax::ast;
use syntax::ast_util;
use syntax::parse::token;
use syntax::codemap::Span;
use syntax::print::pprust;
pub fn check_match(fcx: &FnCtxt,
expr: &ast::Expr,
discrim: &ast::Expr,
arms: &[ast::Arm]) {
let tcx = fcx.ccx.tcx;
let discrim_ty = fcx.infcx().next_ty_var();
check_expr_has_type(fcx, discrim, discrim_ty);
// Typecheck the patterns first, so that we get types for all the
// bindings.
for arm in arms.iter() {
let mut pcx = pat_ctxt {
fcx: fcx,
map: pat_id_map(&tcx.def_map, &**arm.pats.get(0)),
};
for p in arm.pats.iter() { check_pat(&mut pcx, &**p, discrim_ty);}
}
// The result of the match is the common supertype of all the
// arms. Start out the value as bottom, since it's the, well,
// bottom the type lattice, and we'll be moving up the lattice as
// we process each arm. (Note that any match with 0 arms is matching
// on any empty type and is therefore unreachable; should the flow
// of execution reach it, we will fail, so bottom is an appropriate
// type in that case)
let mut result_ty = ty::mk_bot();
// Now typecheck the blocks.
let mut saw_err = ty::type_is_error(discrim_ty);
for arm in arms.iter() {
let mut guard_err = false;
let mut guard_bot = false;
match arm.guard {
Some(ref e) => {
check_expr_has_type(fcx, &**e, ty::mk_bool());
let e_ty = fcx.expr_ty(&**e);
if ty::type_is_error(e_ty) {
guard_err = true;
}
else if ty::type_is_bot(e_ty) {
guard_bot = true;
}
},
None => ()
}
check_expr(fcx, &*arm.body);
let bty = fcx.node_ty(arm.body.id);
saw_err = saw_err || ty::type_is_error(bty);
if guard_err {
fcx.write_error(arm.body.id);
saw_err = true;
}
else if guard_bot {
fcx.write_bot(arm.body.id);
}
result_ty =
infer::common_supertype(
fcx.infcx(),
infer::MatchExpressionArm(expr.span, arm.body.span),
true, // result_ty is "expected" here
result_ty,
bty);
}
if saw_err {
result_ty = ty::mk_err();
} else if ty::type_is_bot(discrim_ty) {
result_ty = ty::mk_bot();
}
fcx.write_ty(expr.id, result_ty);
}
pub struct pat_ctxt<'a> {
pub fcx: &'a FnCtxt<'a>,
pub map: PatIdMap,
}
pub fn check_pat_variant(pcx: &pat_ctxt, pat: &ast::Pat, path: &ast::Path,
subpats: &Option<Vec<Gc<ast::Pat>>>, expected: ty::t) {
// Typecheck the path.
let fcx = pcx.fcx;
let tcx = pcx.fcx.ccx.tcx;
let arg_types: Vec<ty::t> ;
let kind_name;
// structure_of requires type variables to be resolved.
// So when we pass in <expected>, it's an error if it
// contains type variables.
// Check to see whether this is an enum or a struct.
match *structure_of(pcx.fcx, pat.span, expected) {
ty::ty_enum(expected_def_id, ref expected_substs) => {
// Lookup the enum and variant def ids:
let v_def = lookup_def(pcx.fcx, pat.span, pat.id);
match v_def.variant_def_ids() {
Some((enm, var)) => {
// Assign the pattern the type of the *enum*, not the variant.
let enum_tpt = ty::lookup_item_type(tcx, enm);
instantiate_path(pcx.fcx,
path,
enum_tpt,
v_def,
pat.span,
pat.id);
// check that the type of the value being matched is a subtype
// of the type of the pattern:
let pat_ty = fcx.node_ty(pat.id);
demand::subtype(fcx, pat.span, expected, pat_ty);
// Get the expected types of the arguments.
arg_types = {
let vinfo =
ty::enum_variant_with_id(tcx, enm, var);
if enm == expected_def_id {
vinfo.args.iter()
.map(|t| t.subst(tcx, expected_substs))
.collect()
} else {
vinfo.args.iter()
.map(|_| ty::mk_err())
.collect()
}
};
kind_name = "variant";
}
None => {
// See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
fcx.infcx().type_error_message_str_with_expected(pat.span,
|expected, actual| {
expected.map_or("".to_string(), |e| {
format!("mismatched types: expected `{}` but found {}",
e, actual)
})},
Some(expected),
"a structure pattern".to_string(),
None);
fcx.write_error(pat.id);
kind_name = "[error]";
arg_types = subpats.clone()
.unwrap_or_default()
.move_iter()
.map(|_| ty::mk_err())
.collect();
}
}
}
ty::ty_struct(struct_def_id, ref expected_substs) => {
// Lookup the struct ctor def id
let s_def = lookup_def(pcx.fcx, pat.span, pat.id);
let s_def_id = s_def.def_id();
// Assign the pattern the type of the struct.
let ctor_tpt = ty::lookup_item_type(tcx, s_def_id);
let struct_tpt = if ty::is_fn_ty(ctor_tpt.ty) {
ty::ty_param_bounds_and_ty {ty: ty::ty_fn_ret(ctor_tpt.ty),
..ctor_tpt}
} else {
ctor_tpt
};
instantiate_path(pcx.fcx,
path,
struct_tpt,
s_def,
pat.span,
pat.id);
// Check that the type of the value being matched is a subtype of
// the type of the pattern.
let pat_ty = fcx.node_ty(pat.id);
demand::subtype(fcx, pat.span, expected, pat_ty);
// Get the expected types of the arguments.
let class_fields = ty::struct_fields(
tcx, struct_def_id, expected_substs);
arg_types = class_fields.iter().map(|field| field.mt.ty).collect();
kind_name = "structure";
}
_ => {
// See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
fcx.infcx().type_error_message_str_with_expected(pat.span,
|expected, actual| {
expected.map_or("".to_string(),
|e| {
format!("mismatched types: expected `{}` but found {}",
e, actual)
})
},
Some(expected),
"an enum or structure pattern".to_string(),
None);
fcx.write_error(pat.id);
kind_name = "[error]";
arg_types = subpats.clone()
.unwrap_or_default()
.iter()
.map(|_| ty::mk_err())
.collect();
}
}
let arg_len = arg_types.len();
// Count the number of subpatterns.
let subpats_len;
match *subpats {
None => subpats_len = arg_len,
Some(ref subpats) => subpats_len = subpats.len()
}
let mut error_happened = false;
if arg_len > 0 {
// N-ary variant.
if arg_len != subpats_len {
let s = format!("this pattern has {} field{}, \
but the corresponding {} has {} field{}",
subpats_len,
if subpats_len == 1 {""} else {"s"},
kind_name,
arg_len,
if arg_len == 1 {""} else {"s"});
tcx.sess.span_err(pat.span, s.as_slice());
error_happened = true;
}
if !error_happened {
for pats in subpats.iter() {
for (subpat, arg_ty) in pats.iter().zip(arg_types.iter()) {
check_pat(pcx, &**subpat, *arg_ty);
}
}
}
} else if subpats_len > 0 {
tcx.sess.span_err(pat.span,
format!("this pattern has {} field{}, \
but the corresponding {} has no fields",
subpats_len,
if subpats_len == 1 {""} else {"s"},
kind_name).as_slice());
error_happened = true;
}
if error_happened {
for pats in subpats.iter() {
for pat in pats.iter() {
check_pat(pcx, &**pat, ty::mk_err());
}
}
}
}
/// `path` is the AST path item naming the type of this struct.
/// `fields` is the field patterns of the struct pattern.
/// `class_fields` describes the type of each field of the struct.
/// `class_id` is the ID of the struct.
/// `substitutions` are the type substitutions applied to this struct type
/// (e.g. K,V in HashMap<K,V>).
/// `etc` is true if the pattern said '...' and false otherwise.
pub fn check_struct_pat_fields(pcx: &pat_ctxt,
span: Span,
fields: &[ast::FieldPat],
class_fields: Vec<ty::field_ty>,
class_id: ast::DefId,
substitutions: &subst::Substs,
etc: bool) {
let tcx = pcx.fcx.ccx.tcx;
// Index the class fields. The second argument in the tuple is whether the
// field has been bound yet or not.
let mut field_map = HashMap::new();
for (i, class_field) in class_fields.iter().enumerate() {
field_map.insert(class_field.name, (i, false));
}
// Typecheck each field.
let mut found_fields = HashSet::new();
for field in fields.iter() {
match field_map.find_mut(&field.ident.name) {
Some(&(_, true)) => {
tcx.sess.span_err(span,
format!("field `{}` bound twice in pattern",
token::get_ident(field.ident)).as_slice());
}
Some(&(index, ref mut used)) => {
*used = true;
let class_field = *class_fields.get(index);
let field_type = ty::lookup_field_type(tcx,
class_id,
class_field.id,
substitutions);
check_pat(pcx, &*field.pat, field_type);
found_fields.insert(index);
}
None => {
// Check the pattern anyway, so that attempts to look
// up its type won't fail
check_pat(pcx, &*field.pat, ty::mk_err());
tcx.sess.span_err(span,
format!("struct `{}` does not have a field named `{}`",
ty::item_path_str(tcx, class_id),
token::get_ident(field.ident)).as_slice());
}
}
}
// Report an error if not all the fields were specified.
if !etc {
for (i, field) in class_fields.iter().enumerate() {
if found_fields.contains(&i) {
continue;
}
tcx.sess
.span_err(span,
format!("pattern does not mention field `{}`",
token::get_name(field.name)).as_slice());
}
}
}
pub fn check_struct_pat(pcx: &pat_ctxt, pat_id: ast::NodeId, span: Span,
expected: ty::t, path: &ast::Path,
fields: &[ast::FieldPat], etc: bool,
struct_id: ast::DefId,
substitutions: &subst::Substs) {
let fcx = pcx.fcx;
let tcx = pcx.fcx.ccx.tcx;
let class_fields = ty::lookup_struct_fields(tcx, struct_id);
// Check to ensure that the struct is the one specified.
match tcx.def_map.borrow().find(&pat_id) {
Some(&def::DefStruct(supplied_def_id))
if supplied_def_id == struct_id => {
// OK.
}
Some(&def::DefStruct(..)) | Some(&def::DefVariant(..)) => {
let name = pprust::path_to_str(path);
tcx.sess
.span_err(span,
format!("mismatched types: expected `{}` but found \
`{}`",
fcx.infcx().ty_to_str(expected),
name).as_slice());
}
_ => {
tcx.sess.span_bug(span, "resolve didn't write in struct ID");
}
}
check_struct_pat_fields(pcx, span, fields, class_fields, struct_id,
substitutions, etc);
}
pub fn check_struct_like_enum_variant_pat(pcx: &pat_ctxt,
pat_id: ast::NodeId,
span: Span,
expected: ty::t,
path: &ast::Path,
fields: &[ast::FieldPat],
etc: bool,
enum_id: ast::DefId,
substitutions: &subst::Substs) {
let fcx = pcx.fcx;
let tcx = pcx.fcx.ccx.tcx;
// Find the variant that was specified.
match tcx.def_map.borrow().find(&pat_id) {
Some(&def::DefVariant(found_enum_id, variant_id, _))
if found_enum_id == enum_id => {
// Get the struct fields from this struct-like enum variant.
let class_fields = ty::lookup_struct_fields(tcx, variant_id);
check_struct_pat_fields(pcx, span, fields, class_fields,
variant_id, substitutions, etc);
}
Some(&def::DefStruct(..)) | Some(&def::DefVariant(..)) => {
let name = pprust::path_to_str(path);
tcx.sess.span_err(span,
format!("mismatched types: expected `{}` but \
found `{}`",
fcx.infcx().ty_to_str(expected),
name).as_slice());
}
_ => {
tcx.sess.span_bug(span, "resolve didn't write in variant");
}
}
}
// Pattern checking is top-down rather than bottom-up so that bindings get
// their types immediately.
pub fn check_pat(pcx: &pat_ctxt, pat: &ast::Pat, expected: ty::t) {
let fcx = pcx.fcx;
let tcx = pcx.fcx.ccx.tcx;
match pat.node {
ast::PatWild | ast::PatWildMulti => {
fcx.write_ty(pat.id, expected);
}
ast::PatLit(ref lt) => {
check_expr_has_type(fcx, &**lt, expected);
fcx.write_ty(pat.id, fcx.expr_ty(&**lt));
}
ast::PatRange(ref begin, ref end) => {
check_expr_has_type(fcx, &**begin, expected);
check_expr_has_type(fcx, &**end, expected);
let b_ty =
fcx.infcx().resolve_type_vars_if_possible(fcx.expr_ty(&**begin));
let e_ty =
fcx.infcx().resolve_type_vars_if_possible(fcx.expr_ty(&**end));
debug!("pat_range beginning type: {:?}", b_ty);
debug!("pat_range ending type: {:?}", e_ty);
if !require_same_types(
tcx, Some(fcx.infcx()), false, pat.span, b_ty, e_ty,
|| "mismatched types in range".to_string())
{
// no-op
} else if !ty::type_is_numeric(b_ty) && !ty::type_is_char(b_ty) {
tcx.sess.span_err(pat.span,
"only char and numeric types are allowed in range");
} else {
match valid_range_bounds(fcx.ccx, &**begin, &**end) {
Some(false) => {
tcx.sess.span_err(begin.span,
"lower range bound must be less than upper");
},
None => {
tcx.sess.span_err(begin.span,
"mismatched types in range");
},
_ => { },
}
}
fcx.write_ty(pat.id, b_ty);
}
ast::PatEnum(..) |
ast::PatIdent(..) if pat_is_const(&tcx.def_map, pat) => {
let const_did = tcx.def_map.borrow().get_copy(&pat.id).def_id();
let const_tpt = ty::lookup_item_type(tcx, const_did);
demand::suptype(fcx, pat.span, expected, const_tpt.ty);
fcx.write_ty(pat.id, const_tpt.ty);
}
ast::PatIdent(bm, ref name, sub) if pat_is_binding(&tcx.def_map, pat) => {
let typ = fcx.local_ty(pat.span, pat.id);
match bm {
ast::BindByRef(mutbl) => {
// if the binding is like
// ref x | ref const x | ref mut x
// then the type of x is &M T where M is the mutability
// and T is the expected type
let region_var =
fcx.infcx().next_region_var(
infer::PatternRegion(pat.span));
let mt = ty::mt {ty: expected, mutbl: mutbl};
let region_ty = ty::mk_rptr(tcx, region_var, mt);
demand::eqtype(fcx, pat.span, region_ty, typ);
}
// otherwise the type of x is the expected type T
ast::BindByValue(_) => {
demand::eqtype(fcx, pat.span, expected, typ);
}
}
let canon_id = *pcx.map.get(&ast_util::path_to_ident(name));
if canon_id != pat.id {
let ct = fcx.local_ty(pat.span, canon_id);
demand::eqtype(fcx, pat.span, ct, typ);
}
fcx.write_ty(pat.id, typ);
debug!("(checking match) writing type for pat id {}", pat.id);
match sub {
Some(ref p) => check_pat(pcx, &**p, expected),
_ => ()
}
}
ast::PatIdent(_, ref path, _) => {
check_pat_variant(pcx, pat, path, &Some(Vec::new()), expected);
}
ast::PatEnum(ref path, ref subpats) => {
check_pat_variant(pcx, pat, path, subpats, expected);
}
ast::PatStruct(ref path, ref fields, etc) => {
// Grab the class data that we care about.
let structure = structure_of(fcx, pat.span, expected);
let mut error_happened = false;
match *structure {
ty::ty_struct(cid, ref substs) => {
check_struct_pat(pcx, pat.id, pat.span, expected, path,
fields.as_slice(), etc, cid, substs);
}
ty::ty_enum(eid, ref substs) => {
check_struct_like_enum_variant_pat(pcx,
pat.id,
pat.span,
expected,
path,
fields.as_slice(),
etc,
eid,
substs);
}
_ => {
// See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
fcx.infcx().type_error_message_str_with_expected(pat.span,
|expected, actual| {
expected.map_or("".to_string(),
|e| {
format!("mismatched types: expected \
`{}` but found {}", e, actual)
})},
Some(expected),
"a structure pattern".to_string(),
None);
match tcx.def_map.borrow().find(&pat.id) {
Some(&def::DefStruct(supplied_def_id)) => {
check_struct_pat(pcx,
pat.id,
pat.span,
ty::mk_err(),
path,
fields.as_slice(),
etc,
supplied_def_id,
&subst::Substs::empty());
}
_ => () // Error, but we're already in an error case
}
error_happened = true;
}
}
// Finally, write in the type.
if error_happened {
fcx.write_error(pat.id);
} else {
fcx.write_ty(pat.id, expected);
}
}
ast::PatTup(ref elts) => {
let s = structure_of(fcx, pat.span, expected);
let e_count = elts.len();
match *s {
ty::ty_tup(ref ex_elts) if e_count == ex_elts.len() => {
for (i, elt) in elts.iter().enumerate() {
check_pat(pcx, &**elt, *ex_elts.get(i));
}
fcx.write_ty(pat.id, expected);
}
_ => {
for elt in elts.iter() {
check_pat(pcx, &**elt, ty::mk_err());
}
// use terr_tuple_size if both types are tuples
let type_error = match *s {
ty::ty_tup(ref ex_elts) => {
ty::terr_tuple_size(ty::expected_found {
expected: ex_elts.len(),
found: e_count
})
}
_ => ty::terr_mismatch
};
// See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
fcx.infcx().type_error_message_str_with_expected(pat.span,
|expected,
actual| {
expected.map_or("".to_string(), |e| {
format!("mismatched types: expected `{}` \
but found {}", e, actual)
}
)},
Some(expected),
"tuple".to_string(),
Some(&type_error));
fcx.write_error(pat.id);
}
}
}
ast::PatBox(ref inner) => {
check_pointer_pat(pcx, Send, &**inner, pat.id, pat.span, expected);
}
ast::PatRegion(ref inner) => {
check_pointer_pat(pcx, Borrowed, &**inner, pat.id, pat.span, expected);
}
ast::PatVec(ref before, slice, ref after) => {
let default_region_var =
fcx.infcx().next_region_var(
infer::PatternRegion(pat.span));
let check_err = |found: String| {
for &elt in before.iter() {
check_pat(pcx, &*elt, ty::mk_err());
}
for elt in slice.iter() {
check_pat(pcx, &**elt, ty::mk_err());
}
for elt in after.iter() {
check_pat(pcx, &**elt, ty::mk_err());
}
// See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
fcx.infcx().type_error_message_str_with_expected(
pat.span,
|expected, actual| {
expected.map_or("".to_string(),
|e| {
format!("mismatched types: expected `{}` but found {}",
e, actual)
})
},
Some(expected),
found,
None);
fcx.write_error(pat.id);
};
let (elt_type, region_var, mutbl, fixed) = match *structure_of(fcx,
pat.span,
expected) {
ty::ty_vec(mt, Some(fixed)) =>
(mt.ty, default_region_var, ast::MutImmutable, Some(fixed)),
ty::ty_uniq(t) => match ty::get(t).sty {
ty::ty_vec(mt, None) => {
fcx.type_error_message(pat.span,
|_| {
"unique vector patterns are no \
longer supported".to_string()
},
expected,
None);
(mt.ty, default_region_var, ast::MutImmutable, None)
}
_ => {
check_err("a vector pattern".to_string());
return;
}
},
ty::ty_rptr(r, mt) => match ty::get(mt.ty).sty {
ty::ty_vec(mt, None) => (mt.ty, r, mt.mutbl, None),
_ => {
check_err("a vector pattern".to_string());
return;
}
},
_ => {
check_err("a vector pattern".to_string());
return;
}
};
let min_len = before.len() + after.len();
fixed.and_then(|count| match slice {
Some(_) if count < min_len =>
Some(format!("a fixed vector pattern of size at least {}", min_len)),
None if count != min_len =>
Some(format!("a fixed vector pattern of size {}", min_len)),
_ => None
}).map(check_err);
for elt in before.iter() {
check_pat(pcx, &**elt, elt_type);
}
match slice {
Some(ref slice_pat) => {
let slice_ty = ty::mk_slice(tcx,
region_var,
ty::mt {ty: elt_type, mutbl: mutbl});
check_pat(pcx, &**slice_pat, slice_ty);
}
None => ()
}
for elt in after.iter() {
check_pat(pcx, &**elt, elt_type);
}
fcx.write_ty(pat.id, expected);
}
ast::PatMac(_) => tcx.sess.bug("unexpanded macro"),
}
}
// Helper function to check gc, box and & patterns
fn check_pointer_pat(pcx: &pat_ctxt,
pointer_kind: PointerKind,
inner: &ast::Pat,
pat_id: ast::NodeId,
span: Span,
expected: ty::t) {
let fcx = pcx.fcx;
let tcx = fcx.ccx.tcx;
let check_inner: |ty::t| = |e_inner| {
match ty::get(e_inner).sty {
ty::ty_trait(_) if pat_is_binding(&tcx.def_map, inner) => {
// This is "x = SomeTrait" being reduced from
// "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
check_pat(pcx, inner, ty::mk_err());
tcx.sess.span_err(
span,
format!("type `{}` cannot be dereferenced",
fcx.infcx().ty_to_str(expected)).as_slice());
fcx.write_error(pat_id);
}
_ => {
check_pat(pcx, inner, e_inner);
fcx.write_ty(pat_id, expected);
}
}
};
match *structure_of(fcx, span, expected) {
ty::ty_uniq(e_inner) if pointer_kind == Send => {
check_inner(e_inner);
}
ty::ty_rptr(_, e_inner) if pointer_kind == Borrowed => {
check_inner(e_inner.ty);
}
_ => {
check_pat(pcx, inner, ty::mk_err());
// See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
fcx.infcx().type_error_message_str_with_expected(
span,
|expected, actual| {
expected.map_or("".to_string(), |e| {
format!("mismatched types: expected `{}` but found {}",
e, actual)
})
},
Some(expected),
format!("{} pattern", match pointer_kind {
Send => "a box",
Borrowed => "an `&`-pointer",
}),
None);
fcx.write_error(pat_id);
}
}
}
#[deriving(PartialEq)]
pub enum PointerKind {
Send,
Borrowed,
}