1190 lines
45 KiB
Rust
1190 lines
45 KiB
Rust
// Copyright 2012-2014 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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pub use self::Constructor::*;
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use self::Usefulness::*;
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use self::WitnessPreference::*;
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use middle::const_eval::{compare_const_vals, const_bool, const_float, const_val};
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use middle::const_eval::{const_expr_to_pat, eval_const_expr, lookup_const_by_id};
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use middle::def::*;
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use middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor, Init};
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use middle::expr_use_visitor::{JustWrite, LoanCause, MutateMode};
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use middle::expr_use_visitor::{WriteAndRead};
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use middle::expr_use_visitor as euv;
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use middle::mem_categorization::cmt;
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use middle::pat_util::*;
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use middle::ty::*;
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use middle::ty;
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use std::cmp::Ordering;
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use std::fmt;
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use std::iter::{range_inclusive, AdditiveIterator, FromIterator, IntoIterator, repeat};
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use std::num::Float;
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use std::slice;
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use syntax::ast::{self, DUMMY_NODE_ID, NodeId, Pat};
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use syntax::ast_util;
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use syntax::codemap::{Span, Spanned, DUMMY_SP};
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use syntax::fold::{Folder, noop_fold_pat};
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use syntax::print::pprust::pat_to_string;
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use syntax::parse::token;
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use syntax::ptr::P;
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use syntax::visit::{self, Visitor, FnKind};
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use util::ppaux::ty_to_string;
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use util::nodemap::FnvHashMap;
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pub const DUMMY_WILD_PAT: &'static Pat = &Pat {
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id: DUMMY_NODE_ID,
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node: ast::PatWild(ast::PatWildSingle),
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span: DUMMY_SP
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};
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struct Matrix<'a>(Vec<Vec<&'a Pat>>);
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/// Pretty-printer for matrices of patterns, example:
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/// ++++++++++++++++++++++++++
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/// + _ + [] +
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/// ++++++++++++++++++++++++++
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/// + true + [First] +
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/// ++++++++++++++++++++++++++
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/// + true + [Second(true)] +
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/// ++++++++++++++++++++++++++
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/// + false + [_] +
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/// ++++++++++++++++++++++++++
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/// + _ + [_, _, ..tail] +
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/// ++++++++++++++++++++++++++
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impl<'a> fmt::Debug for Matrix<'a> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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try!(write!(f, "\n"));
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let &Matrix(ref m) = self;
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let pretty_printed_matrix: Vec<Vec<String>> = m.iter().map(|row| {
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row.iter()
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.map(|&pat| pat_to_string(&*pat))
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.collect::<Vec<String>>()
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}).collect();
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let column_count = m.iter().map(|row| row.len()).max().unwrap_or(0);
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assert!(m.iter().all(|row| row.len() == column_count));
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let column_widths: Vec<uint> = (0..column_count).map(|col| {
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pretty_printed_matrix.iter().map(|row| row[col].len()).max().unwrap_or(0)
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}).collect();
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let total_width = column_widths.iter().cloned().sum() + column_count * 3 + 1;
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let br = repeat('+').take(total_width).collect::<String>();
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try!(write!(f, "{}\n", br));
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for row in pretty_printed_matrix {
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try!(write!(f, "+"));
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for (column, pat_str) in row.into_iter().enumerate() {
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try!(write!(f, " "));
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try!(write!(f, "{:1$}", pat_str, column_widths[column]));
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try!(write!(f, " +"));
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}
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try!(write!(f, "\n"));
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try!(write!(f, "{}\n", br));
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}
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Ok(())
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}
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}
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impl<'a> FromIterator<Vec<&'a Pat>> for Matrix<'a> {
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fn from_iter<T: IntoIterator<Item=Vec<&'a Pat>>>(iter: T) -> Matrix<'a> {
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Matrix(iter.into_iter().collect())
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}
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}
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pub struct MatchCheckCtxt<'a, 'tcx: 'a> {
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pub tcx: &'a ty::ctxt<'tcx>,
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pub param_env: ParameterEnvironment<'a, 'tcx>,
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}
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#[derive(Clone, PartialEq)]
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pub enum Constructor {
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/// The constructor of all patterns that don't vary by constructor,
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/// e.g. struct patterns and fixed-length arrays.
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Single,
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/// Enum variants.
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Variant(ast::DefId),
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/// Literal values.
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ConstantValue(const_val),
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/// Ranges of literal values (2..5).
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ConstantRange(const_val, const_val),
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/// Array patterns of length n.
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Slice(uint),
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/// Array patterns with a subslice.
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SliceWithSubslice(uint, uint)
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}
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#[derive(Clone, PartialEq)]
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enum Usefulness {
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Useful,
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UsefulWithWitness(Vec<P<Pat>>),
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NotUseful
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}
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#[derive(Copy)]
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enum WitnessPreference {
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ConstructWitness,
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LeaveOutWitness
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}
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impl<'a, 'tcx, 'v> Visitor<'v> for MatchCheckCtxt<'a, 'tcx> {
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fn visit_expr(&mut self, ex: &ast::Expr) {
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check_expr(self, ex);
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}
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fn visit_local(&mut self, l: &ast::Local) {
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check_local(self, l);
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}
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fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v ast::FnDecl,
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b: &'v ast::Block, s: Span, n: NodeId) {
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check_fn(self, fk, fd, b, s, n);
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}
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}
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pub fn check_crate(tcx: &ty::ctxt) {
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visit::walk_crate(&mut MatchCheckCtxt {
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tcx: tcx,
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param_env: ty::empty_parameter_environment(tcx),
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}, tcx.map.krate());
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tcx.sess.abort_if_errors();
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}
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fn check_expr(cx: &mut MatchCheckCtxt, ex: &ast::Expr) {
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visit::walk_expr(cx, ex);
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match ex.node {
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ast::ExprMatch(ref scrut, ref arms, source) => {
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for arm in arms {
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// First, check legality of move bindings.
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check_legality_of_move_bindings(cx,
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arm.guard.is_some(),
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&arm.pats);
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// Second, if there is a guard on each arm, make sure it isn't
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// assigning or borrowing anything mutably.
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match arm.guard {
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Some(ref guard) => check_for_mutation_in_guard(cx, &**guard),
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None => {}
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}
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}
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let mut static_inliner = StaticInliner::new(cx.tcx, None);
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let inlined_arms = arms.iter().map(|arm| {
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(arm.pats.iter().map(|pat| {
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static_inliner.fold_pat((*pat).clone())
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}).collect(), arm.guard.as_ref().map(|e| &**e))
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}).collect::<Vec<(Vec<P<Pat>>, Option<&ast::Expr>)>>();
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// Bail out early if inlining failed.
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if static_inliner.failed {
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return;
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}
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for pat in inlined_arms
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.iter()
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.flat_map(|&(ref pats, _)| pats.iter()) {
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// Third, check legality of move bindings.
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check_legality_of_bindings_in_at_patterns(cx, &**pat);
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// Fourth, check if there are any references to NaN that we should warn about.
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check_for_static_nan(cx, &**pat);
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// Fifth, check if for any of the patterns that match an enumerated type
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// are bindings with the same name as one of the variants of said type.
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check_for_bindings_named_the_same_as_variants(cx, &**pat);
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}
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// Fourth, check for unreachable arms.
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check_arms(cx, &inlined_arms[..], source);
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// Finally, check if the whole match expression is exhaustive.
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// Check for empty enum, because is_useful only works on inhabited types.
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let pat_ty = node_id_to_type(cx.tcx, scrut.id);
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if inlined_arms.is_empty() {
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if !type_is_empty(cx.tcx, pat_ty) {
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// We know the type is inhabited, so this must be wrong
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span_err!(cx.tcx.sess, ex.span, E0002,
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"non-exhaustive patterns: type {} is non-empty",
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ty_to_string(cx.tcx, pat_ty)
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);
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}
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// If the type *is* empty, it's vacuously exhaustive
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return;
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}
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let matrix: Matrix = inlined_arms
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.iter()
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.filter(|&&(_, guard)| guard.is_none())
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.flat_map(|arm| arm.0.iter())
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.map(|pat| vec![&**pat])
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.collect();
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check_exhaustive(cx, ex.span, &matrix, source);
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},
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_ => ()
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}
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}
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fn is_expr_const_nan(tcx: &ty::ctxt, expr: &ast::Expr) -> bool {
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match eval_const_expr(tcx, expr) {
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const_float(f) => f.is_nan(),
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_ => false
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}
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}
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fn check_for_bindings_named_the_same_as_variants(cx: &MatchCheckCtxt, pat: &Pat) {
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ast_util::walk_pat(pat, |p| {
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match p.node {
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ast::PatIdent(ast::BindByValue(ast::MutImmutable), ident, None) => {
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let pat_ty = ty::pat_ty(cx.tcx, p);
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if let ty::ty_enum(def_id, _) = pat_ty.sty {
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let def = cx.tcx.def_map.borrow().get(&p.id).map(|d| d.full_def());
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if let Some(DefLocal(_)) = def {
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if ty::enum_variants(cx.tcx, def_id).iter().any(|variant|
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token::get_name(variant.name) == token::get_name(ident.node.name)
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&& variant.args.len() == 0
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) {
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span_warn!(cx.tcx.sess, p.span, E0170,
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"pattern binding `{}` is named the same as one \
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of the variants of the type `{}`",
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&token::get_ident(ident.node), ty_to_string(cx.tcx, pat_ty));
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span_help!(cx.tcx.sess, p.span,
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"if you meant to match on a variant, \
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consider making the path in the pattern qualified: `{}::{}`",
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ty_to_string(cx.tcx, pat_ty), &token::get_ident(ident.node));
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}
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}
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}
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}
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_ => ()
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}
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true
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});
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}
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// Check that we do not match against a static NaN (#6804)
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fn check_for_static_nan(cx: &MatchCheckCtxt, pat: &Pat) {
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ast_util::walk_pat(pat, |p| {
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match p.node {
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ast::PatLit(ref expr) if is_expr_const_nan(cx.tcx, &**expr) => {
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span_warn!(cx.tcx.sess, p.span, E0003,
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"unmatchable NaN in pattern, \
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use the is_nan method in a guard instead");
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}
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_ => ()
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}
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true
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});
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}
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// Check for unreachable patterns
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fn check_arms(cx: &MatchCheckCtxt,
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arms: &[(Vec<P<Pat>>, Option<&ast::Expr>)],
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source: ast::MatchSource) {
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let mut seen = Matrix(vec![]);
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let mut printed_if_let_err = false;
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for &(ref pats, guard) in arms {
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for pat in pats {
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let v = vec![&**pat];
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match is_useful(cx, &seen, &v[..], LeaveOutWitness) {
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NotUseful => {
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match source {
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ast::MatchSource::IfLetDesugar { .. } => {
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if printed_if_let_err {
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// we already printed an irrefutable if-let pattern error.
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// We don't want two, that's just confusing.
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} else {
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// find the first arm pattern so we can use its span
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let &(ref first_arm_pats, _) = &arms[0];
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let first_pat = &first_arm_pats[0];
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let span = first_pat.span;
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span_err!(cx.tcx.sess, span, E0162, "irrefutable if-let pattern");
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printed_if_let_err = true;
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}
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},
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ast::MatchSource::WhileLetDesugar => {
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// find the first arm pattern so we can use its span
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let &(ref first_arm_pats, _) = &arms[0];
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let first_pat = &first_arm_pats[0];
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let span = first_pat.span;
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span_err!(cx.tcx.sess, span, E0165, "irrefutable while-let pattern");
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},
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ast::MatchSource::ForLoopDesugar => {
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// this is a bug, because on `match iter.next()` we cover
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// `Some(<head>)` and `None`. It's impossible to have an unreachable
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// pattern
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// (see libsyntax/ext/expand.rs for the full expansion of a for loop)
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cx.tcx.sess.span_bug(pat.span, "unreachable for-loop pattern")
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},
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ast::MatchSource::Normal => {
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span_err!(cx.tcx.sess, pat.span, E0001, "unreachable pattern")
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},
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}
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}
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Useful => (),
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UsefulWithWitness(_) => unreachable!()
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}
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if guard.is_none() {
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let Matrix(mut rows) = seen;
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rows.push(v);
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seen = Matrix(rows);
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}
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}
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}
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}
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fn raw_pat<'a>(p: &'a Pat) -> &'a Pat {
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match p.node {
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ast::PatIdent(_, _, Some(ref s)) => raw_pat(&**s),
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_ => p
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}
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}
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fn check_exhaustive(cx: &MatchCheckCtxt, sp: Span, matrix: &Matrix, source: ast::MatchSource) {
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match is_useful(cx, matrix, &[DUMMY_WILD_PAT], ConstructWitness) {
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UsefulWithWitness(pats) => {
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let witness = match &pats[..] {
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[ref witness] => &**witness,
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[] => DUMMY_WILD_PAT,
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_ => unreachable!()
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};
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match source {
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ast::MatchSource::ForLoopDesugar => {
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// `witness` has the form `Some(<head>)`, peel off the `Some`
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let witness = match witness.node {
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ast::PatEnum(_, Some(ref pats)) => match &pats[..] {
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[ref pat] => &**pat,
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_ => unreachable!(),
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},
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_ => unreachable!(),
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};
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span_err!(cx.tcx.sess, sp, E0297,
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"refutable pattern in `for` loop binding: \
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`{}` not covered",
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pat_to_string(witness));
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},
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_ => {
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span_err!(cx.tcx.sess, sp, E0004,
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"non-exhaustive patterns: `{}` not covered",
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pat_to_string(witness)
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);
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},
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}
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}
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NotUseful => {
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// This is good, wildcard pattern isn't reachable
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},
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_ => unreachable!()
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}
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}
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fn const_val_to_expr(value: &const_val) -> P<ast::Expr> {
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let node = match value {
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&const_bool(b) => ast::LitBool(b),
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_ => unreachable!()
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};
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P(ast::Expr {
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id: 0,
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node: ast::ExprLit(P(Spanned { node: node, span: DUMMY_SP })),
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span: DUMMY_SP
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})
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}
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pub struct StaticInliner<'a, 'tcx: 'a> {
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pub tcx: &'a ty::ctxt<'tcx>,
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pub failed: bool,
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pub renaming_map: Option<&'a mut FnvHashMap<(NodeId, Span), NodeId>>,
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}
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impl<'a, 'tcx> StaticInliner<'a, 'tcx> {
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pub fn new<'b>(tcx: &'b ty::ctxt<'tcx>,
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renaming_map: Option<&'b mut FnvHashMap<(NodeId, Span), NodeId>>)
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-> StaticInliner<'b, 'tcx> {
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StaticInliner {
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tcx: tcx,
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failed: false,
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renaming_map: renaming_map
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}
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}
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}
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struct RenamingRecorder<'map> {
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substituted_node_id: NodeId,
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origin_span: Span,
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renaming_map: &'map mut FnvHashMap<(NodeId, Span), NodeId>
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}
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impl<'map> ast_util::IdVisitingOperation for RenamingRecorder<'map> {
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fn visit_id(&mut self, node_id: NodeId) {
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let key = (node_id, self.origin_span);
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self.renaming_map.insert(key, self.substituted_node_id);
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}
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}
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impl<'a, 'tcx> Folder for StaticInliner<'a, 'tcx> {
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fn fold_pat(&mut self, pat: P<Pat>) -> P<Pat> {
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return match pat.node {
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ast::PatIdent(..) | ast::PatEnum(..) => {
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let def = self.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def());
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match def {
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Some(DefConst(did)) => match lookup_const_by_id(self.tcx, did) {
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Some(const_expr) => {
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const_expr_to_pat(self.tcx, const_expr, pat.span).map(|new_pat| {
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if let Some(ref mut renaming_map) = self.renaming_map {
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// Record any renamings we do here
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record_renamings(const_expr, &pat, renaming_map);
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}
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new_pat
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})
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}
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None => {
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self.failed = true;
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span_err!(self.tcx.sess, pat.span, E0158,
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"statics cannot be referenced in patterns");
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pat
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}
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},
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_ => noop_fold_pat(pat, self)
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}
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}
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_ => noop_fold_pat(pat, self)
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};
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fn record_renamings(const_expr: &ast::Expr,
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substituted_pat: &ast::Pat,
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renaming_map: &mut FnvHashMap<(NodeId, Span), NodeId>) {
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let mut renaming_recorder = RenamingRecorder {
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substituted_node_id: substituted_pat.id,
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origin_span: substituted_pat.span,
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renaming_map: renaming_map,
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};
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let mut id_visitor = ast_util::IdVisitor {
|
|
operation: &mut renaming_recorder,
|
|
pass_through_items: true,
|
|
visited_outermost: false,
|
|
};
|
|
|
|
id_visitor.visit_expr(const_expr);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Constructs a partial witness for a pattern given a list of
|
|
/// patterns expanded by the specialization step.
|
|
///
|
|
/// When a pattern P is discovered to be useful, this function is used bottom-up
|
|
/// to reconstruct a complete witness, e.g. a pattern P' that covers a subset
|
|
/// of values, V, where each value in that set is not covered by any previously
|
|
/// used patterns and is covered by the pattern P'. Examples:
|
|
///
|
|
/// left_ty: tuple of 3 elements
|
|
/// pats: [10, 20, _] => (10, 20, _)
|
|
///
|
|
/// left_ty: struct X { a: (bool, &'static str), b: uint}
|
|
/// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 }
|
|
fn construct_witness(cx: &MatchCheckCtxt, ctor: &Constructor,
|
|
pats: Vec<&Pat>, left_ty: Ty) -> P<Pat> {
|
|
let pats_len = pats.len();
|
|
let mut pats = pats.into_iter().map(|p| P((*p).clone()));
|
|
let pat = match left_ty.sty {
|
|
ty::ty_tup(_) => ast::PatTup(pats.collect()),
|
|
|
|
ty::ty_enum(cid, _) | ty::ty_struct(cid, _) => {
|
|
let (vid, is_structure) = match ctor {
|
|
&Variant(vid) =>
|
|
(vid, ty::enum_variant_with_id(cx.tcx, cid, vid).arg_names.is_some()),
|
|
_ =>
|
|
(cid, !ty::is_tuple_struct(cx.tcx, cid))
|
|
};
|
|
if is_structure {
|
|
let fields = ty::lookup_struct_fields(cx.tcx, vid);
|
|
let field_pats: Vec<_> = fields.into_iter()
|
|
.zip(pats)
|
|
.filter(|&(_, ref pat)| pat.node != ast::PatWild(ast::PatWildSingle))
|
|
.map(|(field, pat)| Spanned {
|
|
span: DUMMY_SP,
|
|
node: ast::FieldPat {
|
|
ident: ast::Ident::new(field.name),
|
|
pat: pat,
|
|
is_shorthand: false,
|
|
}
|
|
}).collect();
|
|
let has_more_fields = field_pats.len() < pats_len;
|
|
ast::PatStruct(def_to_path(cx.tcx, vid), field_pats, has_more_fields)
|
|
} else {
|
|
ast::PatEnum(def_to_path(cx.tcx, vid), Some(pats.collect()))
|
|
}
|
|
}
|
|
|
|
ty::ty_rptr(_, ty::mt { ty, mutbl }) => {
|
|
match ty.sty {
|
|
ty::ty_vec(_, Some(n)) => match ctor {
|
|
&Single => {
|
|
assert_eq!(pats_len, n);
|
|
ast::PatVec(pats.collect(), None, vec!())
|
|
},
|
|
_ => unreachable!()
|
|
},
|
|
ty::ty_vec(_, None) => match ctor {
|
|
&Slice(n) => {
|
|
assert_eq!(pats_len, n);
|
|
ast::PatVec(pats.collect(), None, vec!())
|
|
},
|
|
_ => unreachable!()
|
|
},
|
|
ty::ty_str => ast::PatWild(ast::PatWildSingle),
|
|
|
|
_ => {
|
|
assert_eq!(pats_len, 1);
|
|
ast::PatRegion(pats.nth(0).unwrap(), mutbl)
|
|
}
|
|
}
|
|
}
|
|
|
|
ty::ty_vec(_, Some(len)) => {
|
|
assert_eq!(pats_len, len);
|
|
ast::PatVec(pats.collect(), None, vec![])
|
|
}
|
|
|
|
_ => {
|
|
match *ctor {
|
|
ConstantValue(ref v) => ast::PatLit(const_val_to_expr(v)),
|
|
_ => ast::PatWild(ast::PatWildSingle),
|
|
}
|
|
}
|
|
};
|
|
|
|
P(ast::Pat {
|
|
id: 0,
|
|
node: pat,
|
|
span: DUMMY_SP
|
|
})
|
|
}
|
|
|
|
fn missing_constructor(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix,
|
|
left_ty: Ty, max_slice_length: uint) -> Option<Constructor> {
|
|
let used_constructors: Vec<Constructor> = rows.iter()
|
|
.flat_map(|row| pat_constructors(cx, row[0], left_ty, max_slice_length).into_iter())
|
|
.collect();
|
|
all_constructors(cx, left_ty, max_slice_length)
|
|
.into_iter()
|
|
.find(|c| !used_constructors.contains(c))
|
|
}
|
|
|
|
/// This determines the set of all possible constructors of a pattern matching
|
|
/// values of type `left_ty`. For vectors, this would normally be an infinite set
|
|
/// but is instead bounded by the maximum fixed length of slice patterns in
|
|
/// the column of patterns being analyzed.
|
|
fn all_constructors(cx: &MatchCheckCtxt, left_ty: Ty,
|
|
max_slice_length: uint) -> Vec<Constructor> {
|
|
match left_ty.sty {
|
|
ty::ty_bool =>
|
|
[true, false].iter().map(|b| ConstantValue(const_bool(*b))).collect(),
|
|
|
|
ty::ty_rptr(_, ty::mt { ty, .. }) => match ty.sty {
|
|
ty::ty_vec(_, None) =>
|
|
range_inclusive(0, max_slice_length).map(|length| Slice(length)).collect(),
|
|
_ => vec!(Single)
|
|
},
|
|
|
|
ty::ty_enum(eid, _) =>
|
|
ty::enum_variants(cx.tcx, eid)
|
|
.iter()
|
|
.map(|va| Variant(va.id))
|
|
.collect(),
|
|
|
|
_ =>
|
|
vec!(Single)
|
|
}
|
|
}
|
|
|
|
// Algorithm from http://moscova.inria.fr/~maranget/papers/warn/index.html
|
|
//
|
|
// Whether a vector `v` of patterns is 'useful' in relation to a set of such
|
|
// vectors `m` is defined as there being a set of inputs that will match `v`
|
|
// but not any of the sets in `m`.
|
|
//
|
|
// This is used both for reachability checking (if a pattern isn't useful in
|
|
// relation to preceding patterns, it is not reachable) and exhaustiveness
|
|
// checking (if a wildcard pattern is useful in relation to a matrix, the
|
|
// matrix isn't exhaustive).
|
|
|
|
// Note: is_useful doesn't work on empty types, as the paper notes.
|
|
// So it assumes that v is non-empty.
|
|
fn is_useful(cx: &MatchCheckCtxt,
|
|
matrix: &Matrix,
|
|
v: &[&Pat],
|
|
witness: WitnessPreference)
|
|
-> Usefulness {
|
|
let &Matrix(ref rows) = matrix;
|
|
debug!("{:?}", matrix);
|
|
if rows.len() == 0 {
|
|
return match witness {
|
|
ConstructWitness => UsefulWithWitness(vec!()),
|
|
LeaveOutWitness => Useful
|
|
};
|
|
}
|
|
if rows[0].len() == 0 {
|
|
return NotUseful;
|
|
}
|
|
let real_pat = match rows.iter().find(|r| (*r)[0].id != DUMMY_NODE_ID) {
|
|
Some(r) => raw_pat(r[0]),
|
|
None if v.len() == 0 => return NotUseful,
|
|
None => v[0]
|
|
};
|
|
let left_ty = if real_pat.id == DUMMY_NODE_ID {
|
|
ty::mk_nil(cx.tcx)
|
|
} else {
|
|
ty::pat_ty(cx.tcx, &*real_pat)
|
|
};
|
|
|
|
let max_slice_length = rows.iter().filter_map(|row| match row[0].node {
|
|
ast::PatVec(ref before, _, ref after) => Some(before.len() + after.len()),
|
|
_ => None
|
|
}).max().map_or(0, |v| v + 1);
|
|
|
|
let constructors = pat_constructors(cx, v[0], left_ty, max_slice_length);
|
|
if constructors.is_empty() {
|
|
match missing_constructor(cx, matrix, left_ty, max_slice_length) {
|
|
None => {
|
|
all_constructors(cx, left_ty, max_slice_length).into_iter().map(|c| {
|
|
match is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness) {
|
|
UsefulWithWitness(pats) => UsefulWithWitness({
|
|
let arity = constructor_arity(cx, &c, left_ty);
|
|
let mut result = {
|
|
let pat_slice = &pats[..];
|
|
let subpats: Vec<_> = (0..arity).map(|i| {
|
|
pat_slice.get(i).map_or(DUMMY_WILD_PAT, |p| &**p)
|
|
}).collect();
|
|
vec![construct_witness(cx, &c, subpats, left_ty)]
|
|
};
|
|
result.extend(pats.into_iter().skip(arity));
|
|
result
|
|
}),
|
|
result => result
|
|
}
|
|
}).find(|result| result != &NotUseful).unwrap_or(NotUseful)
|
|
},
|
|
|
|
Some(constructor) => {
|
|
let matrix = rows.iter().filter_map(|r| {
|
|
if pat_is_binding_or_wild(&cx.tcx.def_map, raw_pat(r[0])) {
|
|
Some(r.tail().to_vec())
|
|
} else {
|
|
None
|
|
}
|
|
}).collect();
|
|
match is_useful(cx, &matrix, v.tail(), witness) {
|
|
UsefulWithWitness(pats) => {
|
|
let arity = constructor_arity(cx, &constructor, left_ty);
|
|
let wild_pats: Vec<_> = repeat(DUMMY_WILD_PAT).take(arity).collect();
|
|
let enum_pat = construct_witness(cx, &constructor, wild_pats, left_ty);
|
|
let mut new_pats = vec![enum_pat];
|
|
new_pats.extend(pats.into_iter());
|
|
UsefulWithWitness(new_pats)
|
|
},
|
|
result => result
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
constructors.into_iter().map(|c|
|
|
is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness)
|
|
).find(|result| result != &NotUseful).unwrap_or(NotUseful)
|
|
}
|
|
}
|
|
|
|
fn is_useful_specialized(cx: &MatchCheckCtxt, &Matrix(ref m): &Matrix,
|
|
v: &[&Pat], ctor: Constructor, lty: Ty,
|
|
witness: WitnessPreference) -> Usefulness {
|
|
let arity = constructor_arity(cx, &ctor, lty);
|
|
let matrix = Matrix(m.iter().filter_map(|r| {
|
|
specialize(cx, &r[..], &ctor, 0, arity)
|
|
}).collect());
|
|
match specialize(cx, v, &ctor, 0, arity) {
|
|
Some(v) => is_useful(cx, &matrix, &v[..], witness),
|
|
None => NotUseful
|
|
}
|
|
}
|
|
|
|
/// Determines the constructors that the given pattern can be specialized to.
|
|
///
|
|
/// In most cases, there's only one constructor that a specific pattern
|
|
/// represents, such as a specific enum variant or a specific literal value.
|
|
/// Slice patterns, however, can match slices of different lengths. For instance,
|
|
/// `[a, b, ..tail]` can match a slice of length 2, 3, 4 and so on.
|
|
///
|
|
/// On the other hand, a wild pattern and an identifier pattern cannot be
|
|
/// specialized in any way.
|
|
fn pat_constructors(cx: &MatchCheckCtxt, p: &Pat,
|
|
left_ty: Ty, max_slice_length: uint) -> Vec<Constructor> {
|
|
let pat = raw_pat(p);
|
|
match pat.node {
|
|
ast::PatIdent(..) =>
|
|
match cx.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) {
|
|
Some(DefConst(..)) =>
|
|
cx.tcx.sess.span_bug(pat.span, "const pattern should've \
|
|
been rewritten"),
|
|
Some(DefStruct(_)) => vec!(Single),
|
|
Some(DefVariant(_, id, _)) => vec!(Variant(id)),
|
|
_ => vec!()
|
|
},
|
|
ast::PatEnum(..) =>
|
|
match cx.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) {
|
|
Some(DefConst(..)) =>
|
|
cx.tcx.sess.span_bug(pat.span, "const pattern should've \
|
|
been rewritten"),
|
|
Some(DefVariant(_, id, _)) => vec!(Variant(id)),
|
|
_ => vec!(Single)
|
|
},
|
|
ast::PatStruct(..) =>
|
|
match cx.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) {
|
|
Some(DefConst(..)) =>
|
|
cx.tcx.sess.span_bug(pat.span, "const pattern should've \
|
|
been rewritten"),
|
|
Some(DefVariant(_, id, _)) => vec!(Variant(id)),
|
|
_ => vec!(Single)
|
|
},
|
|
ast::PatLit(ref expr) =>
|
|
vec!(ConstantValue(eval_const_expr(cx.tcx, &**expr))),
|
|
ast::PatRange(ref lo, ref hi) =>
|
|
vec!(ConstantRange(eval_const_expr(cx.tcx, &**lo), eval_const_expr(cx.tcx, &**hi))),
|
|
ast::PatVec(ref before, ref slice, ref after) =>
|
|
match left_ty.sty {
|
|
ty::ty_vec(_, Some(_)) => vec!(Single),
|
|
_ => if slice.is_some() {
|
|
range_inclusive(before.len() + after.len(), max_slice_length)
|
|
.map(|length| Slice(length))
|
|
.collect()
|
|
} else {
|
|
vec!(Slice(before.len() + after.len()))
|
|
}
|
|
},
|
|
ast::PatBox(_) | ast::PatTup(_) | ast::PatRegion(..) =>
|
|
vec!(Single),
|
|
ast::PatWild(_) =>
|
|
vec!(),
|
|
ast::PatMac(_) =>
|
|
cx.tcx.sess.bug("unexpanded macro")
|
|
}
|
|
}
|
|
|
|
/// This computes the arity of a constructor. The arity of a constructor
|
|
/// is how many subpattern patterns of that constructor should be expanded to.
|
|
///
|
|
/// For instance, a tuple pattern (_, 42, Some([])) has the arity of 3.
|
|
/// A struct pattern's arity is the number of fields it contains, etc.
|
|
pub fn constructor_arity(cx: &MatchCheckCtxt, ctor: &Constructor, ty: Ty) -> uint {
|
|
match ty.sty {
|
|
ty::ty_tup(ref fs) => fs.len(),
|
|
ty::ty_uniq(_) => 1,
|
|
ty::ty_rptr(_, ty::mt { ty, .. }) => match ty.sty {
|
|
ty::ty_vec(_, None) => match *ctor {
|
|
Slice(length) => length,
|
|
ConstantValue(_) => 0,
|
|
_ => unreachable!()
|
|
},
|
|
ty::ty_str => 0,
|
|
_ => 1
|
|
},
|
|
ty::ty_enum(eid, _) => {
|
|
match *ctor {
|
|
Variant(id) => enum_variant_with_id(cx.tcx, eid, id).args.len(),
|
|
_ => unreachable!()
|
|
}
|
|
}
|
|
ty::ty_struct(cid, _) => ty::lookup_struct_fields(cx.tcx, cid).len(),
|
|
ty::ty_vec(_, Some(n)) => n,
|
|
_ => 0
|
|
}
|
|
}
|
|
|
|
fn range_covered_by_constructor(ctor: &Constructor,
|
|
from: &const_val, to: &const_val) -> Option<bool> {
|
|
let (c_from, c_to) = match *ctor {
|
|
ConstantValue(ref value) => (value, value),
|
|
ConstantRange(ref from, ref to) => (from, to),
|
|
Single => return Some(true),
|
|
_ => unreachable!()
|
|
};
|
|
let cmp_from = compare_const_vals(c_from, from);
|
|
let cmp_to = compare_const_vals(c_to, to);
|
|
match (cmp_from, cmp_to) {
|
|
(Some(cmp_from), Some(cmp_to)) => {
|
|
Some(cmp_from != Ordering::Less && cmp_to != Ordering::Greater)
|
|
}
|
|
_ => None
|
|
}
|
|
}
|
|
|
|
/// This is the main specialization step. It expands the first pattern in the given row
|
|
/// into `arity` patterns based on the constructor. For most patterns, the step is trivial,
|
|
/// for instance tuple patterns are flattened and box patterns expand into their inner pattern.
|
|
///
|
|
/// OTOH, slice patterns with a subslice pattern (..tail) can be expanded into multiple
|
|
/// different patterns.
|
|
/// Structure patterns with a partial wild pattern (Foo { a: 42, .. }) have their missing
|
|
/// fields filled with wild patterns.
|
|
pub fn specialize<'a>(cx: &MatchCheckCtxt, r: &[&'a Pat],
|
|
constructor: &Constructor, col: uint, arity: uint) -> Option<Vec<&'a Pat>> {
|
|
let &Pat {
|
|
id: pat_id, ref node, span: pat_span
|
|
} = raw_pat(r[col]);
|
|
let head: Option<Vec<&Pat>> = match *node {
|
|
ast::PatWild(_) =>
|
|
Some(repeat(DUMMY_WILD_PAT).take(arity).collect()),
|
|
|
|
ast::PatIdent(_, _, _) => {
|
|
let opt_def = cx.tcx.def_map.borrow().get(&pat_id).map(|d| d.full_def());
|
|
match opt_def {
|
|
Some(DefConst(..)) =>
|
|
cx.tcx.sess.span_bug(pat_span, "const pattern should've \
|
|
been rewritten"),
|
|
Some(DefVariant(_, id, _)) => if *constructor == Variant(id) {
|
|
Some(vec!())
|
|
} else {
|
|
None
|
|
},
|
|
_ => Some(repeat(DUMMY_WILD_PAT).take(arity).collect())
|
|
}
|
|
}
|
|
|
|
ast::PatEnum(_, ref args) => {
|
|
let def = cx.tcx.def_map.borrow()[pat_id].full_def();
|
|
match def {
|
|
DefConst(..) =>
|
|
cx.tcx.sess.span_bug(pat_span, "const pattern should've \
|
|
been rewritten"),
|
|
DefVariant(_, id, _) if *constructor != Variant(id) => None,
|
|
DefVariant(..) | DefStruct(..) => {
|
|
Some(match args {
|
|
&Some(ref args) => args.iter().map(|p| &**p).collect(),
|
|
&None => repeat(DUMMY_WILD_PAT).take(arity).collect(),
|
|
})
|
|
}
|
|
_ => None
|
|
}
|
|
}
|
|
|
|
ast::PatStruct(_, ref pattern_fields, _) => {
|
|
// Is this a struct or an enum variant?
|
|
let def = cx.tcx.def_map.borrow()[pat_id].full_def();
|
|
let class_id = match def {
|
|
DefConst(..) =>
|
|
cx.tcx.sess.span_bug(pat_span, "const pattern should've \
|
|
been rewritten"),
|
|
DefVariant(_, variant_id, _) => if *constructor == Variant(variant_id) {
|
|
Some(variant_id)
|
|
} else {
|
|
None
|
|
},
|
|
_ => {
|
|
// Assume this is a struct.
|
|
match ty::ty_to_def_id(node_id_to_type(cx.tcx, pat_id)) {
|
|
None => {
|
|
cx.tcx.sess.span_bug(pat_span,
|
|
"struct pattern wasn't of a \
|
|
type with a def ID?!")
|
|
}
|
|
Some(def_id) => Some(def_id),
|
|
}
|
|
}
|
|
};
|
|
class_id.map(|variant_id| {
|
|
let struct_fields = ty::lookup_struct_fields(cx.tcx, variant_id);
|
|
let args = struct_fields.iter().map(|sf| {
|
|
match pattern_fields.iter().find(|f| f.node.ident.name == sf.name) {
|
|
Some(ref f) => &*f.node.pat,
|
|
_ => DUMMY_WILD_PAT
|
|
}
|
|
}).collect();
|
|
args
|
|
})
|
|
}
|
|
|
|
ast::PatTup(ref args) =>
|
|
Some(args.iter().map(|p| &**p).collect()),
|
|
|
|
ast::PatBox(ref inner) | ast::PatRegion(ref inner, _) =>
|
|
Some(vec![&**inner]),
|
|
|
|
ast::PatLit(ref expr) => {
|
|
let expr_value = eval_const_expr(cx.tcx, &**expr);
|
|
match range_covered_by_constructor(constructor, &expr_value, &expr_value) {
|
|
Some(true) => Some(vec![]),
|
|
Some(false) => None,
|
|
None => {
|
|
span_err!(cx.tcx.sess, pat_span, E0298, "mismatched types between arms");
|
|
None
|
|
}
|
|
}
|
|
}
|
|
|
|
ast::PatRange(ref from, ref to) => {
|
|
let from_value = eval_const_expr(cx.tcx, &**from);
|
|
let to_value = eval_const_expr(cx.tcx, &**to);
|
|
match range_covered_by_constructor(constructor, &from_value, &to_value) {
|
|
Some(true) => Some(vec![]),
|
|
Some(false) => None,
|
|
None => {
|
|
span_err!(cx.tcx.sess, pat_span, E0299, "mismatched types between arms");
|
|
None
|
|
}
|
|
}
|
|
}
|
|
|
|
ast::PatVec(ref before, ref slice, ref after) => {
|
|
match *constructor {
|
|
// Fixed-length vectors.
|
|
Single => {
|
|
let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect();
|
|
pats.extend(repeat(DUMMY_WILD_PAT).take(arity - before.len() - after.len()));
|
|
pats.extend(after.iter().map(|p| &**p));
|
|
Some(pats)
|
|
},
|
|
Slice(length) if before.len() + after.len() <= length && slice.is_some() => {
|
|
let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect();
|
|
pats.extend(repeat(DUMMY_WILD_PAT).take(arity - before.len() - after.len()));
|
|
pats.extend(after.iter().map(|p| &**p));
|
|
Some(pats)
|
|
},
|
|
Slice(length) if before.len() + after.len() == length => {
|
|
let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect();
|
|
pats.extend(after.iter().map(|p| &**p));
|
|
Some(pats)
|
|
},
|
|
SliceWithSubslice(prefix, suffix)
|
|
if before.len() == prefix
|
|
&& after.len() == suffix
|
|
&& slice.is_some() => {
|
|
let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect();
|
|
pats.extend(after.iter().map(|p| &**p));
|
|
Some(pats)
|
|
}
|
|
_ => None
|
|
}
|
|
}
|
|
|
|
ast::PatMac(_) => {
|
|
span_err!(cx.tcx.sess, pat_span, E0300, "unexpanded macro");
|
|
None
|
|
}
|
|
};
|
|
head.map(|mut head| {
|
|
head.push_all(&r[..col]);
|
|
head.push_all(&r[col + 1..]);
|
|
head
|
|
})
|
|
}
|
|
|
|
fn check_local(cx: &mut MatchCheckCtxt, loc: &ast::Local) {
|
|
visit::walk_local(cx, loc);
|
|
|
|
let name = match loc.source {
|
|
ast::LocalLet => "local",
|
|
ast::LocalFor => "`for` loop"
|
|
};
|
|
|
|
let mut static_inliner = StaticInliner::new(cx.tcx, None);
|
|
is_refutable(cx, &*static_inliner.fold_pat(loc.pat.clone()), |pat| {
|
|
span_err!(cx.tcx.sess, loc.pat.span, E0005,
|
|
"refutable pattern in {} binding: `{}` not covered",
|
|
name, pat_to_string(pat)
|
|
);
|
|
});
|
|
|
|
// Check legality of move bindings and `@` patterns.
|
|
check_legality_of_move_bindings(cx, false, slice::ref_slice(&loc.pat));
|
|
check_legality_of_bindings_in_at_patterns(cx, &*loc.pat);
|
|
}
|
|
|
|
fn check_fn(cx: &mut MatchCheckCtxt,
|
|
kind: FnKind,
|
|
decl: &ast::FnDecl,
|
|
body: &ast::Block,
|
|
sp: Span,
|
|
fn_id: NodeId) {
|
|
match kind {
|
|
visit::FkFnBlock => {}
|
|
_ => cx.param_env = ParameterEnvironment::for_item(cx.tcx, fn_id),
|
|
}
|
|
|
|
visit::walk_fn(cx, kind, decl, body, sp);
|
|
|
|
for input in &decl.inputs {
|
|
is_refutable(cx, &*input.pat, |pat| {
|
|
span_err!(cx.tcx.sess, input.pat.span, E0006,
|
|
"refutable pattern in function argument: `{}` not covered",
|
|
pat_to_string(pat)
|
|
);
|
|
});
|
|
check_legality_of_move_bindings(cx, false, slice::ref_slice(&input.pat));
|
|
check_legality_of_bindings_in_at_patterns(cx, &*input.pat);
|
|
}
|
|
}
|
|
|
|
fn is_refutable<A, F>(cx: &MatchCheckCtxt, pat: &Pat, refutable: F) -> Option<A> where
|
|
F: FnOnce(&Pat) -> A,
|
|
{
|
|
let pats = Matrix(vec!(vec!(pat)));
|
|
match is_useful(cx, &pats, &[DUMMY_WILD_PAT], ConstructWitness) {
|
|
UsefulWithWitness(pats) => {
|
|
assert_eq!(pats.len(), 1);
|
|
Some(refutable(&*pats[0]))
|
|
},
|
|
NotUseful => None,
|
|
Useful => unreachable!()
|
|
}
|
|
}
|
|
|
|
// Legality of move bindings checking
|
|
fn check_legality_of_move_bindings(cx: &MatchCheckCtxt,
|
|
has_guard: bool,
|
|
pats: &[P<Pat>]) {
|
|
let tcx = cx.tcx;
|
|
let def_map = &tcx.def_map;
|
|
let mut by_ref_span = None;
|
|
for pat in pats {
|
|
pat_bindings(def_map, &**pat, |bm, _, span, _path| {
|
|
match bm {
|
|
ast::BindByRef(_) => {
|
|
by_ref_span = Some(span);
|
|
}
|
|
ast::BindByValue(_) => {
|
|
}
|
|
}
|
|
})
|
|
}
|
|
|
|
let check_move = |p: &Pat, sub: Option<&Pat>| {
|
|
// check legality of moving out of the enum
|
|
|
|
// x @ Foo(..) is legal, but x @ Foo(y) isn't.
|
|
if sub.map_or(false, |p| pat_contains_bindings(def_map, &*p)) {
|
|
span_err!(cx.tcx.sess, p.span, E0007, "cannot bind by-move with sub-bindings");
|
|
} else if has_guard {
|
|
span_err!(cx.tcx.sess, p.span, E0008, "cannot bind by-move into a pattern guard");
|
|
} else if by_ref_span.is_some() {
|
|
span_err!(cx.tcx.sess, p.span, E0009,
|
|
"cannot bind by-move and by-ref in the same pattern");
|
|
span_note!(cx.tcx.sess, by_ref_span.unwrap(), "by-ref binding occurs here");
|
|
}
|
|
};
|
|
|
|
for pat in pats {
|
|
ast_util::walk_pat(&**pat, |p| {
|
|
if pat_is_binding(def_map, &*p) {
|
|
match p.node {
|
|
ast::PatIdent(ast::BindByValue(_), _, ref sub) => {
|
|
let pat_ty = ty::node_id_to_type(tcx, p.id);
|
|
if ty::type_moves_by_default(&cx.param_env, pat.span, pat_ty) {
|
|
check_move(p, sub.as_ref().map(|p| &**p));
|
|
}
|
|
}
|
|
ast::PatIdent(ast::BindByRef(_), _, _) => {
|
|
}
|
|
_ => {
|
|
cx.tcx.sess.span_bug(
|
|
p.span,
|
|
&format!("binding pattern {} is not an \
|
|
identifier: {:?}",
|
|
p.id,
|
|
p.node));
|
|
}
|
|
}
|
|
}
|
|
true
|
|
});
|
|
}
|
|
}
|
|
|
|
/// Ensures that a pattern guard doesn't borrow by mutable reference or
|
|
/// assign.
|
|
fn check_for_mutation_in_guard<'a, 'tcx>(cx: &'a MatchCheckCtxt<'a, 'tcx>,
|
|
guard: &ast::Expr) {
|
|
let mut checker = MutationChecker {
|
|
cx: cx,
|
|
};
|
|
let mut visitor = ExprUseVisitor::new(&mut checker,
|
|
&checker.cx.param_env);
|
|
visitor.walk_expr(guard);
|
|
}
|
|
|
|
struct MutationChecker<'a, 'tcx: 'a> {
|
|
cx: &'a MatchCheckCtxt<'a, 'tcx>,
|
|
}
|
|
|
|
impl<'a, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'tcx> {
|
|
fn matched_pat(&mut self, _: &Pat, _: cmt, _: euv::MatchMode) {}
|
|
fn consume(&mut self, _: NodeId, _: Span, _: cmt, _: ConsumeMode) {}
|
|
fn consume_pat(&mut self, _: &Pat, _: cmt, _: ConsumeMode) {}
|
|
fn borrow(&mut self,
|
|
_: NodeId,
|
|
span: Span,
|
|
_: cmt,
|
|
_: Region,
|
|
kind: BorrowKind,
|
|
_: LoanCause) {
|
|
match kind {
|
|
MutBorrow => {
|
|
span_err!(self.cx.tcx.sess, span, E0301,
|
|
"cannot mutably borrow in a pattern guard")
|
|
}
|
|
ImmBorrow | UniqueImmBorrow => {}
|
|
}
|
|
}
|
|
fn decl_without_init(&mut self, _: NodeId, _: Span) {}
|
|
fn mutate(&mut self, _: NodeId, span: Span, _: cmt, mode: MutateMode) {
|
|
match mode {
|
|
JustWrite | WriteAndRead => {
|
|
span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard")
|
|
}
|
|
Init => {}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Forbids bindings in `@` patterns. This is necessary for memory safety,
|
|
/// because of the way rvalues are handled in the borrow check. (See issue
|
|
/// #14587.)
|
|
fn check_legality_of_bindings_in_at_patterns(cx: &MatchCheckCtxt, pat: &Pat) {
|
|
AtBindingPatternVisitor { cx: cx, bindings_allowed: true }.visit_pat(pat);
|
|
}
|
|
|
|
struct AtBindingPatternVisitor<'a, 'b:'a, 'tcx:'b> {
|
|
cx: &'a MatchCheckCtxt<'b, 'tcx>,
|
|
bindings_allowed: bool
|
|
}
|
|
|
|
impl<'a, 'b, 'tcx, 'v> Visitor<'v> for AtBindingPatternVisitor<'a, 'b, 'tcx> {
|
|
fn visit_pat(&mut self, pat: &Pat) {
|
|
if !self.bindings_allowed && pat_is_binding(&self.cx.tcx.def_map, pat) {
|
|
span_err!(self.cx.tcx.sess, pat.span, E0303,
|
|
"pattern bindings are not allowed \
|
|
after an `@`");
|
|
}
|
|
|
|
match pat.node {
|
|
ast::PatIdent(_, _, Some(_)) => {
|
|
let bindings_were_allowed = self.bindings_allowed;
|
|
self.bindings_allowed = false;
|
|
visit::walk_pat(self, pat);
|
|
self.bindings_allowed = bindings_were_allowed;
|
|
}
|
|
_ => visit::walk_pat(self, pat),
|
|
}
|
|
}
|
|
}
|