split the exhaustiveness-checking logic to its own module
`check_match` is now left with its grab bag of random checks.
This commit is contained in:
Ariel Ben-Yehuda
parent
48387c8bd9
commit
abae5e7e25
696
src/librustc_const_eval/_match.rs
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696
src/librustc_const_eval/_match.rs
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@ -0,0 +1,696 @@
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// Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use self::Constructor::*;
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use self::Usefulness::*;
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use self::WitnessPreference::*;
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use rustc::middle::const_val::ConstVal;
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use eval::{eval_const_expr, compare_const_vals};
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use rustc::hir::def::*;
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use rustc::hir::def_id::{DefId};
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use rustc::hir::pat_util::def_to_path;
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use rustc::ty::{self, Ty, TyCtxt};
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use std::cmp::Ordering;
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use std::fmt;
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use std::iter::{FromIterator, IntoIterator, repeat};
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use rustc::hir;
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use rustc::hir::{Pat, PatKind};
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use rustc::hir::print::pat_to_string;
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use rustc::util::common::ErrorReported;
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use syntax::ast::{self, DUMMY_NODE_ID};
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use syntax::codemap::Spanned;
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use syntax::ptr::P;
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use syntax_pos::{Span, DUMMY_SP};
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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: PatKind::Wild,
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span: DUMMY_SP
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};
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pub const DUMMY_WILD_PATTERN : Pattern<'static, 'static> = Pattern {
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pat: DUMMY_WILD_PAT,
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pattern_ty: None
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};
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#[derive(Copy, Clone)]
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pub struct Pattern<'a, 'tcx> {
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pat: &'a Pat,
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pattern_ty: Option<Ty<'tcx>>
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}
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impl<'a, 'tcx> Pattern<'a, 'tcx> {
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fn as_raw(self) -> &'a Pat {
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let mut pat = self.pat;
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while let PatKind::Binding(.., Some(ref s)) = pat.node {
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pat = s;
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}
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return pat;
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}
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pub fn span(self) -> Span {
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self.pat.span
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}
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}
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impl<'a, 'tcx> fmt::Debug for Pattern<'a, 'tcx> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "{}: {:?}", pat_to_string(self.pat), self.pattern_ty)
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}
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}
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pub struct Matrix<'a, 'tcx>(Vec<Vec<Pattern<'a, 'tcx>>>);
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impl<'a, 'tcx> Matrix<'a, 'tcx> {
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pub fn empty() -> Self {
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Matrix(vec![])
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}
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pub fn push(&mut self, row: Vec<Pattern<'a, 'tcx>>) {
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self.0.push(row)
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}
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}
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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, 'tcx> fmt::Debug for Matrix<'a, 'tcx> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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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().map(|pat| format!("{:?}", pat)).collect()
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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<usize> = (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::<usize>() + column_count * 3 + 1;
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let br = repeat('+').take(total_width).collect::<String>();
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write!(f, "{}\n", br)?;
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for row in pretty_printed_matrix {
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write!(f, "+")?;
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for (column, pat_str) in row.into_iter().enumerate() {
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write!(f, " ")?;
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write!(f, "{:1$}", pat_str, column_widths[column])?;
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write!(f, " +")?;
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}
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write!(f, "\n")?;
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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, 'tcx> FromIterator<Vec<Pattern<'a, 'tcx>>> for Matrix<'a, 'tcx> {
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fn from_iter<T: IntoIterator<Item=Vec<Pattern<'a, 'tcx>>>>(iter: T) -> Self
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{
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Matrix(iter.into_iter().collect())
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}
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}
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//NOTE: appears to be the only place other then InferCtxt to contain a ParamEnv
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pub struct MatchCheckCtxt<'a, 'tcx: 'a> {
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pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
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pub param_env: ty::ParameterEnvironment<'tcx>,
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}
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#[derive(Clone, Debug, 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(DefId),
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/// Literal values.
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ConstantValue(ConstVal),
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/// Ranges of literal values (2..5).
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ConstantRange(ConstVal, ConstVal),
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/// Array patterns of length n.
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Slice(usize),
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}
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impl Constructor {
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fn variant_for_adt<'tcx, 'container, 'a>(&self,
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adt: &'a ty::AdtDefData<'tcx, 'container>)
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-> &'a ty::VariantDefData<'tcx, 'container> {
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match self {
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&Variant(vid) => adt.variant_with_id(vid),
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_ => adt.struct_variant()
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}
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}
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}
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#[derive(Clone, PartialEq)]
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pub 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, Clone)]
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pub enum WitnessPreference {
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ConstructWitness,
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LeaveOutWitness
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}
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fn const_val_to_expr(value: &ConstVal) -> P<hir::Expr> {
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let node = match value {
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&ConstVal::Bool(b) => ast::LitKind::Bool(b),
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_ => bug!()
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};
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P(hir::Expr {
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id: DUMMY_NODE_ID,
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node: hir::ExprLit(P(Spanned { node: node, span: DUMMY_SP })),
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span: DUMMY_SP,
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attrs: ast::ThinVec::new(),
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})
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}
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/// Constructs a partial witness for a pattern given a list of
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/// patterns expanded by the specialization step.
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///
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/// When a pattern P is discovered to be useful, this function is used bottom-up
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/// to reconstruct a complete witness, e.g. a pattern P' that covers a subset
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/// of values, V, where each value in that set is not covered by any previously
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/// used patterns and is covered by the pattern P'. Examples:
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///
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/// left_ty: tuple of 3 elements
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/// pats: [10, 20, _] => (10, 20, _)
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///
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/// left_ty: struct X { a: (bool, &'static str), b: usize}
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/// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 }
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fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor,
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pats: Vec<&Pat>, left_ty: Ty<'tcx>) -> P<Pat> {
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let pats_len = pats.len();
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let mut pats = pats.into_iter().map(|p| P((*p).clone()));
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let pat = match left_ty.sty {
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ty::TyTuple(..) => PatKind::Tuple(pats.collect(), None),
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ty::TyAdt(adt, _) => {
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let v = ctor.variant_for_adt(adt);
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match v.ctor_kind {
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CtorKind::Fictive => {
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let field_pats: hir::HirVec<_> = v.fields.iter()
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.zip(pats)
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.filter(|&(_, ref pat)| pat.node != PatKind::Wild)
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.map(|(field, pat)| Spanned {
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span: DUMMY_SP,
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node: hir::FieldPat {
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name: field.name,
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pat: pat,
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is_shorthand: false,
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}
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}).collect();
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let has_more_fields = field_pats.len() < pats_len;
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PatKind::Struct(def_to_path(cx.tcx, v.did), field_pats, has_more_fields)
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}
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CtorKind::Fn => {
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PatKind::TupleStruct(def_to_path(cx.tcx, v.did), pats.collect(), None)
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}
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CtorKind::Const => {
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PatKind::Path(None, def_to_path(cx.tcx, v.did))
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}
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}
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}
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ty::TyRef(_, ty::TypeAndMut { mutbl, .. }) => {
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assert_eq!(pats_len, 1);
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PatKind::Ref(pats.nth(0).unwrap(), mutbl)
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}
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ty::TySlice(_) => match ctor {
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&Slice(n) => {
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assert_eq!(pats_len, n);
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PatKind::Slice(pats.collect(), None, hir::HirVec::new())
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},
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_ => unreachable!()
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},
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ty::TyArray(_, len) => {
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assert_eq!(pats_len, len);
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PatKind::Slice(pats.collect(), None, hir::HirVec::new())
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}
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_ => {
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match *ctor {
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ConstantValue(ref v) => PatKind::Lit(const_val_to_expr(v)),
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_ => PatKind::Wild,
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}
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}
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};
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P(hir::Pat {
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id: DUMMY_NODE_ID,
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node: pat,
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span: DUMMY_SP
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})
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}
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fn missing_constructors(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix,
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left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
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let used_constructors: Vec<Constructor> = rows.iter()
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.flat_map(|row| pat_constructors(cx, row[0], left_ty, max_slice_length))
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.collect();
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all_constructors(cx, left_ty, max_slice_length)
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.into_iter()
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.filter(|c| !used_constructors.contains(c))
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.collect()
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}
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/// This determines the set of all possible constructors of a pattern matching
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/// values of type `left_ty`. For vectors, this would normally be an infinite set
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/// but is instead bounded by the maximum fixed length of slice patterns in
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/// the column of patterns being analyzed.
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fn all_constructors(_cx: &MatchCheckCtxt, left_ty: Ty,
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max_slice_length: usize) -> Vec<Constructor> {
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match left_ty.sty {
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ty::TyBool =>
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[true, false].iter().map(|b| ConstantValue(ConstVal::Bool(*b))).collect(),
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ty::TySlice(_) =>
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(0..max_slice_length+1).map(|length| Slice(length)).collect(),
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ty::TyAdt(def, _) if def.is_enum() =>
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def.variants.iter().map(|v| Variant(v.did)).collect(),
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_ => vec![Single]
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}
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}
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// Algorithm from http://moscova.inria.fr/~maranget/papers/warn/index.html
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//
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// Whether a vector `v` of patterns is 'useful' in relation to a set of such
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// vectors `m` is defined as there being a set of inputs that will match `v`
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// but not any of the sets in `m`.
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//
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// This is used both for reachability checking (if a pattern isn't useful in
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// relation to preceding patterns, it is not reachable) and exhaustiveness
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// checking (if a wildcard pattern is useful in relation to a matrix, the
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// matrix isn't exhaustive).
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// Note: is_useful doesn't work on empty types, as the paper notes.
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// So it assumes that v is non-empty.
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pub fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
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matrix: &Matrix<'a, 'tcx>,
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v: &[Pattern<'a, 'tcx>],
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witness: WitnessPreference)
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-> Usefulness {
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let &Matrix(ref rows) = matrix;
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debug!("is_useful({:?}, {:?})", matrix, v);
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if rows.is_empty() {
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return match witness {
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ConstructWitness => UsefulWithWitness(vec!()),
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LeaveOutWitness => Useful
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};
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}
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if rows[0].is_empty() {
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return NotUseful;
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}
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assert!(rows.iter().all(|r| r.len() == v.len()));
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let left_ty = match rows.iter().filter_map(|r| r[0].pattern_ty).next()
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.or_else(|| v[0].pattern_ty)
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{
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Some(ty) => ty,
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None => {
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// all patterns are wildcards - we can pick any type we want
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cx.tcx.types.bool
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}
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};
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let max_slice_length = rows.iter().filter_map(|row| match row[0].pat.node {
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PatKind::Slice(ref before, _, ref after) => Some(before.len() + after.len()),
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_ => None
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}).max().map_or(0, |v| v + 1);
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let constructors = pat_constructors(cx, v[0], left_ty, max_slice_length);
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debug!("is_useful - pat_constructors = {:?} left_ty = {:?}", constructors,
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left_ty);
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if constructors.is_empty() {
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let constructors = missing_constructors(cx, matrix, left_ty, max_slice_length);
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debug!("is_useful - missing_constructors = {:?}", constructors);
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if constructors.is_empty() {
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all_constructors(cx, left_ty, max_slice_length).into_iter().map(|c| {
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match is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness) {
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UsefulWithWitness(pats) => UsefulWithWitness({
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let arity = constructor_arity(cx, &c, left_ty);
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let mut result = {
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let pat_slice = &pats[..];
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let subpats: Vec<_> = (0..arity).map(|i| {
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pat_slice.get(i).map_or(DUMMY_WILD_PAT, |p| &**p)
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}).collect();
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vec![construct_witness(cx, &c, subpats, left_ty)]
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};
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result.extend(pats.into_iter().skip(arity));
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result
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}),
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result => result
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}
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}).find(|result| result != &NotUseful).unwrap_or(NotUseful)
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} else {
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let matrix = rows.iter().filter_map(|r| {
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match r[0].as_raw().node {
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PatKind::Binding(..) | PatKind::Wild => Some(r[1..].to_vec()),
|
||||
_ => None,
|
||||
}
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}).collect();
|
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match is_useful(cx, &matrix, &v[1..], witness) {
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UsefulWithWitness(pats) => {
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let mut new_pats: Vec<_> = constructors.into_iter().map(|constructor| {
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let arity = constructor_arity(cx, &constructor, left_ty);
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let wild_pats = vec![DUMMY_WILD_PAT; arity];
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construct_witness(cx, &constructor, wild_pats, left_ty)
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}).collect();
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new_pats.extend(pats);
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UsefulWithWitness(new_pats)
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||||
},
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||||
result => result
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||||
}
|
||||
}
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} else {
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constructors.into_iter().map(|c|
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is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness)
|
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).find(|result| result != &NotUseful).unwrap_or(NotUseful)
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||||
}
|
||||
}
|
||||
|
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fn is_useful_specialized<'a, 'tcx>(
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cx: &MatchCheckCtxt<'a, 'tcx>,
|
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&Matrix(ref m): &Matrix<'a, 'tcx>,
|
||||
v: &[Pattern<'a, 'tcx>],
|
||||
ctor: Constructor,
|
||||
lty: Ty<'tcx>,
|
||||
witness: WitnessPreference) -> Usefulness
|
||||
{
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let arity = constructor_arity(cx, &ctor, lty);
|
||||
let matrix = Matrix(m.iter().filter_map(|r| {
|
||||
specialize(cx, &r[..], &ctor, 0, arity)
|
||||
}).collect());
|
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match specialize(cx, v, &ctor, 0, arity) {
|
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Some(v) => is_useful(cx, &matrix, &v[..], witness),
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None => NotUseful
|
||||
}
|
||||
}
|
||||
|
||||
/// Determines the constructors that the given pattern can be specialized to.
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||||
///
|
||||
/// 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: Pattern,
|
||||
left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
|
||||
let pat = p.as_raw();
|
||||
match pat.node {
|
||||
PatKind::Struct(..) | PatKind::TupleStruct(..) | PatKind::Path(..) =>
|
||||
match cx.tcx.expect_def(pat.id) {
|
||||
Def::Variant(id) | Def::VariantCtor(id, _) => vec![Variant(id)],
|
||||
Def::Struct(..) | Def::StructCtor(..) | Def::Union(..) |
|
||||
Def::TyAlias(..) | Def::AssociatedTy(..) => vec![Single],
|
||||
Def::Const(..) | Def::AssociatedConst(..) =>
|
||||
span_bug!(p.span(), "const pattern should've been rewritten"),
|
||||
def => span_bug!(p.span(), "pat_constructors: unexpected definition {:?}", def),
|
||||
},
|
||||
PatKind::Lit(ref expr) =>
|
||||
vec![ConstantValue(eval_const_expr(cx.tcx, &expr))],
|
||||
PatKind::Range(ref lo, ref hi) =>
|
||||
vec![ConstantRange(eval_const_expr(cx.tcx, &lo), eval_const_expr(cx.tcx, &hi))],
|
||||
PatKind::Slice(ref before, ref slice, ref after) =>
|
||||
match left_ty.sty {
|
||||
ty::TyArray(..) => vec![Single],
|
||||
ty::TySlice(_) if slice.is_some() => {
|
||||
(before.len() + after.len()..max_slice_length+1)
|
||||
.map(|length| Slice(length))
|
||||
.collect()
|
||||
}
|
||||
ty::TySlice(_) => vec!(Slice(before.len() + after.len())),
|
||||
_ => span_bug!(pat.span, "pat_constructors: unexpected \
|
||||
slice pattern type {:?}", left_ty)
|
||||
},
|
||||
PatKind::Box(..) | PatKind::Tuple(..) | PatKind::Ref(..) =>
|
||||
vec![Single],
|
||||
PatKind::Binding(..) | PatKind::Wild =>
|
||||
vec![],
|
||||
}
|
||||
}
|
||||
|
||||
/// 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) -> usize {
|
||||
debug!("constructor_arity({:?}, {:?})", ctor, ty);
|
||||
match ty.sty {
|
||||
ty::TyTuple(ref fs) => fs.len(),
|
||||
ty::TyBox(_) => 1,
|
||||
ty::TySlice(_) => match *ctor {
|
||||
Slice(length) => length,
|
||||
ConstantValue(_) => {
|
||||
// TODO: this is utterly wrong, but required for byte arrays
|
||||
0
|
||||
}
|
||||
_ => bug!("bad slice pattern {:?} {:?}", ctor, ty)
|
||||
},
|
||||
ty::TyRef(..) => 1,
|
||||
ty::TyAdt(adt, _) => {
|
||||
ctor.variant_for_adt(adt).fields.len()
|
||||
}
|
||||
ty::TyArray(_, n) => n,
|
||||
_ => 0
|
||||
}
|
||||
}
|
||||
|
||||
fn range_covered_by_constructor(tcx: TyCtxt, span: Span,
|
||||
ctor: &Constructor,
|
||||
from: &ConstVal, to: &ConstVal)
|
||||
-> Result<bool, ErrorReported> {
|
||||
let (c_from, c_to) = match *ctor {
|
||||
ConstantValue(ref value) => (value, value),
|
||||
ConstantRange(ref from, ref to) => (from, to),
|
||||
Single => return Ok(true),
|
||||
_ => bug!()
|
||||
};
|
||||
let cmp_from = compare_const_vals(tcx, span, c_from, from)?;
|
||||
let cmp_to = compare_const_vals(tcx, span, c_to, to)?;
|
||||
Ok(cmp_from != Ordering::Less && cmp_to != Ordering::Greater)
|
||||
}
|
||||
|
||||
pub fn wrap_pat<'a, 'b, 'tcx>(cx: &MatchCheckCtxt<'b, 'tcx>,
|
||||
pat: &'a Pat)
|
||||
-> Pattern<'a, 'tcx>
|
||||
{
|
||||
let pat_ty = cx.tcx.pat_ty(pat);
|
||||
Pattern {
|
||||
pat: pat,
|
||||
pattern_ty: Some(match pat.node {
|
||||
PatKind::Binding(hir::BindByRef(..), ..) => {
|
||||
pat_ty.builtin_deref(false, ty::NoPreference).unwrap().ty
|
||||
}
|
||||
_ => pat_ty
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
/// 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.
|
||||
fn specialize<'a, 'b, 'tcx>(
|
||||
cx: &MatchCheckCtxt<'b, 'tcx>,
|
||||
r: &[Pattern<'a, 'tcx>],
|
||||
constructor: &Constructor, col: usize, arity: usize)
|
||||
-> Option<Vec<Pattern<'a, 'tcx>>>
|
||||
{
|
||||
let pat = r[col].as_raw();
|
||||
let &Pat {
|
||||
id: pat_id, ref node, span: pat_span
|
||||
} = pat;
|
||||
let wpat = |pat: &'a Pat| wrap_pat(cx, pat);
|
||||
|
||||
let head: Option<Vec<Pattern>> = match *node {
|
||||
PatKind::Binding(..) | PatKind::Wild =>
|
||||
Some(vec![DUMMY_WILD_PATTERN; arity]),
|
||||
|
||||
PatKind::Path(..) => {
|
||||
match cx.tcx.expect_def(pat_id) {
|
||||
Def::Const(..) | Def::AssociatedConst(..) =>
|
||||
span_bug!(pat_span, "const pattern should've \
|
||||
been rewritten"),
|
||||
Def::VariantCtor(id, CtorKind::Const) if *constructor != Variant(id) => None,
|
||||
Def::VariantCtor(_, CtorKind::Const) |
|
||||
Def::StructCtor(_, CtorKind::Const) => Some(Vec::new()),
|
||||
def => span_bug!(pat_span, "specialize: unexpected \
|
||||
definition {:?}", def),
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::TupleStruct(_, ref args, ddpos) => {
|
||||
match cx.tcx.expect_def(pat_id) {
|
||||
Def::Const(..) | Def::AssociatedConst(..) =>
|
||||
span_bug!(pat_span, "const pattern should've \
|
||||
been rewritten"),
|
||||
Def::VariantCtor(id, CtorKind::Fn) if *constructor != Variant(id) => None,
|
||||
Def::VariantCtor(_, CtorKind::Fn) |
|
||||
Def::StructCtor(_, CtorKind::Fn) => {
|
||||
match ddpos {
|
||||
Some(ddpos) => {
|
||||
let mut pats: Vec<_> = args[..ddpos].iter().map(|p| {
|
||||
wpat(p)
|
||||
}).collect();
|
||||
pats.extend(repeat(DUMMY_WILD_PATTERN).take(arity - args.len()));
|
||||
pats.extend(args[ddpos..].iter().map(|p| wpat(p)));
|
||||
Some(pats)
|
||||
}
|
||||
None => Some(args.iter().map(|p| wpat(p)).collect())
|
||||
}
|
||||
}
|
||||
def => span_bug!(pat_span, "specialize: unexpected definition: {:?}", def)
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Struct(_, ref pattern_fields, _) => {
|
||||
let adt = cx.tcx.node_id_to_type(pat_id).ty_adt_def().unwrap();
|
||||
let variant = constructor.variant_for_adt(adt);
|
||||
let def_variant = adt.variant_of_def(cx.tcx.expect_def(pat_id));
|
||||
if variant.did == def_variant.did {
|
||||
Some(variant.fields.iter().map(|sf| {
|
||||
match pattern_fields.iter().find(|f| f.node.name == sf.name) {
|
||||
Some(ref f) => wpat(&f.node.pat),
|
||||
_ => DUMMY_WILD_PATTERN
|
||||
}
|
||||
}).collect())
|
||||
} else {
|
||||
None
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Tuple(ref args, Some(ddpos)) => {
|
||||
let mut pats: Vec<_> = args[..ddpos].iter().map(|p| wpat(p)).collect();
|
||||
pats.extend(repeat(DUMMY_WILD_PATTERN).take(arity - args.len()));
|
||||
pats.extend(args[ddpos..].iter().map(|p| wpat(p)));
|
||||
Some(pats)
|
||||
}
|
||||
PatKind::Tuple(ref args, None) =>
|
||||
Some(args.iter().map(|p| wpat(&**p)).collect()),
|
||||
|
||||
PatKind::Box(ref inner) | PatKind::Ref(ref inner, _) =>
|
||||
Some(vec![wpat(&**inner)]),
|
||||
|
||||
PatKind::Lit(ref expr) => {
|
||||
match r[col].pattern_ty {
|
||||
Some(&ty::TyS { sty: ty::TyRef(_, mt), .. }) => {
|
||||
// HACK: handle string literals. A string literal pattern
|
||||
// serves both as an unary reference pattern and as a
|
||||
// nullary value pattern, depending on the type.
|
||||
Some(vec![Pattern {
|
||||
pat: pat,
|
||||
pattern_ty: Some(mt.ty)
|
||||
}])
|
||||
}
|
||||
Some(ty) => {
|
||||
assert_eq!(constructor_arity(cx, constructor, ty), 0);
|
||||
let expr_value = eval_const_expr(cx.tcx, &expr);
|
||||
match range_covered_by_constructor(
|
||||
cx.tcx, expr.span, constructor, &expr_value, &expr_value
|
||||
) {
|
||||
Ok(true) => Some(vec![]),
|
||||
Ok(false) => None,
|
||||
Err(ErrorReported) => None,
|
||||
}
|
||||
}
|
||||
None => span_bug!(pat.span, "literal pattern {:?} has no type", pat)
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Range(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(
|
||||
cx.tcx, pat_span, constructor, &from_value, &to_value
|
||||
) {
|
||||
Ok(true) => Some(vec![]),
|
||||
Ok(false) => None,
|
||||
Err(ErrorReported) => None,
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Slice(ref before, ref slice, ref after) => {
|
||||
let pat_len = before.len() + after.len();
|
||||
match *constructor {
|
||||
Single => {
|
||||
// Fixed-length vectors.
|
||||
Some(
|
||||
before.iter().map(|p| wpat(p)).chain(
|
||||
repeat(DUMMY_WILD_PATTERN).take(arity - pat_len).chain(
|
||||
after.iter().map(|p| wpat(p))
|
||||
)).collect())
|
||||
},
|
||||
Slice(length) if pat_len <= length && slice.is_some() => {
|
||||
Some(
|
||||
before.iter().map(|p| wpat(p)).chain(
|
||||
repeat(DUMMY_WILD_PATTERN).take(arity - pat_len).chain(
|
||||
after.iter().map(|p| wpat(p))
|
||||
)).collect())
|
||||
}
|
||||
Slice(length) if pat_len == length => {
|
||||
Some(
|
||||
before.iter().map(|p| wpat(p)).chain(
|
||||
after.iter().map(|p| wpat(p))
|
||||
).collect())
|
||||
}
|
||||
_ => None
|
||||
}
|
||||
}
|
||||
};
|
||||
debug!("specialize({:?}, {:?}) = {:?}", r[col], arity, head);
|
||||
|
||||
head.map(|mut head| {
|
||||
head.extend_from_slice(&r[..col]);
|
||||
head.extend_from_slice(&r[col + 1..]);
|
||||
head
|
||||
})
|
||||
}
|
||||
|
||||
pub fn is_refutable<A, F>(cx: &MatchCheckCtxt, pat: &Pat, refutable: F)
|
||||
-> Option<A> where
|
||||
F: FnOnce(&Pat) -> A,
|
||||
{
|
||||
let pats = Matrix(vec!(vec!(wrap_pat(cx, pat))));
|
||||
match is_useful(cx, &pats, &[DUMMY_WILD_PATTERN], ConstructWitness) {
|
||||
UsefulWithWitness(pats) => Some(refutable(&pats[0])),
|
||||
NotUseful => None,
|
||||
Useful => bug!()
|
||||
}
|
||||
}
|
||||
@ -8,169 +8,41 @@
|
||||
// option. This file may not be copied, modified, or distributed
|
||||
// except according to those terms.
|
||||
|
||||
use self::Constructor::*;
|
||||
use self::Usefulness::*;
|
||||
use self::WitnessPreference::*;
|
||||
use _match::{MatchCheckCtxt, Matrix, wrap_pat, is_refutable, is_useful};
|
||||
use _match::{DUMMY_WILD_PATTERN, DUMMY_WILD_PAT};
|
||||
use _match::Usefulness::*;
|
||||
use _match::WitnessPreference::*;
|
||||
|
||||
use eval::report_const_eval_err;
|
||||
use eval::{eval_const_expr_partial, const_expr_to_pat, lookup_const_by_id};
|
||||
use eval::EvalHint::ExprTypeChecked;
|
||||
|
||||
use rustc::dep_graph::DepNode;
|
||||
|
||||
use rustc::hir::pat_util::{pat_bindings, pat_contains_bindings};
|
||||
|
||||
use rustc::middle::const_val::ConstVal;
|
||||
use ::{eval_const_expr, eval_const_expr_partial, compare_const_vals};
|
||||
use ::{const_expr_to_pat, lookup_const_by_id};
|
||||
use ::EvalHint::ExprTypeChecked;
|
||||
use eval::report_const_eval_err;
|
||||
use rustc::hir::def::*;
|
||||
use rustc::hir::def_id::{DefId};
|
||||
use rustc::middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor};
|
||||
use rustc::middle::expr_use_visitor::{LoanCause, MutateMode};
|
||||
use rustc::middle::expr_use_visitor as euv;
|
||||
use rustc::middle::mem_categorization::{cmt};
|
||||
use rustc::hir::pat_util::*;
|
||||
use rustc::session::Session;
|
||||
use rustc::traits::Reveal;
|
||||
use rustc::ty::{self, Ty, TyCtxt};
|
||||
use rustc::ty::{self, TyCtxt};
|
||||
use rustc_errors::DiagnosticBuilder;
|
||||
use std::cmp::Ordering;
|
||||
use std::fmt;
|
||||
use std::iter::{FromIterator, IntoIterator, repeat};
|
||||
|
||||
use rustc::hir;
|
||||
use rustc::hir::{Pat, PatKind};
|
||||
use rustc::hir::def::*;
|
||||
use rustc::hir::intravisit::{self, Visitor, FnKind};
|
||||
use rustc::hir::print::pat_to_string;
|
||||
use rustc::hir::{self, Pat, PatKind};
|
||||
|
||||
use rustc_back::slice;
|
||||
|
||||
use syntax::ast::{self, DUMMY_NODE_ID, NodeId};
|
||||
use syntax::ast;
|
||||
use syntax::codemap::Spanned;
|
||||
use syntax_pos::{Span, DUMMY_SP};
|
||||
use rustc::hir::print::pat_to_string;
|
||||
use syntax::ptr::P;
|
||||
use syntax::util::move_map::MoveMap;
|
||||
use rustc::util::common::ErrorReported;
|
||||
|
||||
pub const DUMMY_WILD_PAT: &'static Pat = &Pat {
|
||||
id: DUMMY_NODE_ID,
|
||||
node: PatKind::Wild,
|
||||
span: DUMMY_SP
|
||||
};
|
||||
|
||||
pub const DUMMY_WILD_PATTERN : Pattern<'static, 'static> = Pattern {
|
||||
pat: DUMMY_WILD_PAT,
|
||||
pattern_ty: None
|
||||
};
|
||||
|
||||
#[derive(Copy, Clone)]
|
||||
pub struct Pattern<'a, 'tcx> {
|
||||
pat: &'a Pat,
|
||||
pattern_ty: Option<Ty<'tcx>>
|
||||
}
|
||||
|
||||
impl<'a, 'tcx> Pattern<'a, 'tcx> {
|
||||
fn as_raw(self) -> &'a Pat {
|
||||
let mut pat = self.pat;
|
||||
|
||||
while let PatKind::Binding(.., Some(ref s)) = pat.node {
|
||||
pat = s;
|
||||
}
|
||||
|
||||
return pat;
|
||||
}
|
||||
|
||||
fn span(self) -> Span {
|
||||
self.pat.span
|
||||
}
|
||||
}
|
||||
|
||||
struct Matrix<'a, 'tcx>(Vec<Vec<Pattern<'a, 'tcx>>>);
|
||||
|
||||
impl<'a, 'tcx> fmt::Debug for Pattern<'a, 'tcx> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||||
write!(f, "{}: {:?}", pat_to_string(self.pat), self.pattern_ty)
|
||||
}
|
||||
}
|
||||
|
||||
/// Pretty-printer for matrices of patterns, example:
|
||||
/// ++++++++++++++++++++++++++
|
||||
/// + _ + [] +
|
||||
/// ++++++++++++++++++++++++++
|
||||
/// + true + [First] +
|
||||
/// ++++++++++++++++++++++++++
|
||||
/// + true + [Second(true)] +
|
||||
/// ++++++++++++++++++++++++++
|
||||
/// + false + [_] +
|
||||
/// ++++++++++++++++++++++++++
|
||||
/// + _ + [_, _, ..tail] +
|
||||
/// ++++++++++++++++++++++++++
|
||||
impl<'a, 'tcx> fmt::Debug for Matrix<'a, 'tcx> {
|
||||
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
||||
write!(f, "\n")?;
|
||||
|
||||
let &Matrix(ref m) = self;
|
||||
let pretty_printed_matrix: Vec<Vec<String>> = m.iter().map(|row| {
|
||||
row.iter().map(|pat| format!("{:?}", pat)).collect()
|
||||
}).collect();
|
||||
|
||||
let column_count = m.iter().map(|row| row.len()).max().unwrap_or(0);
|
||||
assert!(m.iter().all(|row| row.len() == column_count));
|
||||
let column_widths: Vec<usize> = (0..column_count).map(|col| {
|
||||
pretty_printed_matrix.iter().map(|row| row[col].len()).max().unwrap_or(0)
|
||||
}).collect();
|
||||
|
||||
let total_width = column_widths.iter().cloned().sum::<usize>() + column_count * 3 + 1;
|
||||
let br = repeat('+').take(total_width).collect::<String>();
|
||||
write!(f, "{}\n", br)?;
|
||||
for row in pretty_printed_matrix {
|
||||
write!(f, "+")?;
|
||||
for (column, pat_str) in row.into_iter().enumerate() {
|
||||
write!(f, " ")?;
|
||||
write!(f, "{:1$}", pat_str, column_widths[column])?;
|
||||
write!(f, " +")?;
|
||||
}
|
||||
write!(f, "\n")?;
|
||||
write!(f, "{}\n", br)?;
|
||||
}
|
||||
Ok(())
|
||||
}
|
||||
}
|
||||
|
||||
impl<'a, 'tcx> FromIterator<Vec<Pattern<'a, 'tcx>>> for Matrix<'a, 'tcx> {
|
||||
fn from_iter<T: IntoIterator<Item=Vec<Pattern<'a, 'tcx>>>>(iter: T) -> Self
|
||||
{
|
||||
Matrix(iter.into_iter().collect())
|
||||
}
|
||||
}
|
||||
|
||||
//NOTE: appears to be the only place other then InferCtxt to contain a ParamEnv
|
||||
pub struct MatchCheckCtxt<'a, 'tcx: 'a> {
|
||||
pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
||||
pub param_env: ty::ParameterEnvironment<'tcx>,
|
||||
}
|
||||
|
||||
#[derive(Clone, Debug, PartialEq)]
|
||||
pub enum Constructor {
|
||||
/// The constructor of all patterns that don't vary by constructor,
|
||||
/// e.g. struct patterns and fixed-length arrays.
|
||||
Single,
|
||||
/// Enum variants.
|
||||
Variant(DefId),
|
||||
/// Literal values.
|
||||
ConstantValue(ConstVal),
|
||||
/// Ranges of literal values (2..5).
|
||||
ConstantRange(ConstVal, ConstVal),
|
||||
/// Array patterns of length n.
|
||||
Slice(usize),
|
||||
}
|
||||
|
||||
#[derive(Clone, PartialEq)]
|
||||
enum Usefulness {
|
||||
Useful,
|
||||
UsefulWithWitness(Vec<P<Pat>>),
|
||||
NotUseful
|
||||
}
|
||||
|
||||
#[derive(Copy, Clone)]
|
||||
enum WitnessPreference {
|
||||
ConstructWitness,
|
||||
LeaveOutWitness
|
||||
}
|
||||
use syntax_pos::Span;
|
||||
|
||||
impl<'a, 'tcx, 'v> Visitor<'v> for MatchCheckCtxt<'a, 'tcx> {
|
||||
fn visit_expr(&mut self, ex: &hir::Expr) {
|
||||
@ -180,7 +52,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for MatchCheckCtxt<'a, 'tcx> {
|
||||
check_local(self, l);
|
||||
}
|
||||
fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v hir::FnDecl,
|
||||
b: &'v hir::Block, s: Span, n: NodeId) {
|
||||
b: &'v hir::Block, s: Span, n: ast::NodeId) {
|
||||
check_fn(self, fk, fd, b, s, n);
|
||||
}
|
||||
}
|
||||
@ -341,7 +213,7 @@ fn pat_is_catchall(dm: &DefMap, pat: &Pat) -> bool {
|
||||
fn check_arms(cx: &MatchCheckCtxt,
|
||||
arms: &[(Vec<P<Pat>>, Option<&hir::Expr>)],
|
||||
source: hir::MatchSource) {
|
||||
let mut seen = Matrix(vec![]);
|
||||
let mut seen = Matrix::empty();
|
||||
let mut catchall = None;
|
||||
let mut printed_if_let_err = false;
|
||||
for &(ref pats, guard) in arms {
|
||||
@ -390,7 +262,7 @@ fn check_arms(cx: &MatchCheckCtxt,
|
||||
hir::MatchSource::Normal => {
|
||||
let mut err = struct_span_err!(cx.tcx.sess, pat.span, E0001,
|
||||
"unreachable pattern");
|
||||
err.span_label(pat.span, &format!("this is an unreachable pattern"));
|
||||
err.span_label(pat.span, &"this is an unreachable pattern");
|
||||
// if we had a catchall pattern, hint at that
|
||||
if let Some(catchall) = catchall {
|
||||
err.span_note(catchall, "this pattern matches any value");
|
||||
@ -407,13 +279,10 @@ fn check_arms(cx: &MatchCheckCtxt,
|
||||
UsefulWithWitness(_) => bug!()
|
||||
}
|
||||
if guard.is_none() {
|
||||
let Matrix(mut rows) = seen;
|
||||
rows.push(v);
|
||||
seen = Matrix(rows);
|
||||
seen.push(v);
|
||||
if catchall.is_none() && pat_is_catchall(&cx.tcx.def_map.borrow(), pat) {
|
||||
catchall = Some(pat.span);
|
||||
}
|
||||
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -485,18 +354,6 @@ fn check_exhaustive<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
|
||||
}
|
||||
}
|
||||
|
||||
fn const_val_to_expr(value: &ConstVal) -> P<hir::Expr> {
|
||||
let node = match value {
|
||||
&ConstVal::Bool(b) => ast::LitKind::Bool(b),
|
||||
_ => bug!()
|
||||
};
|
||||
P(hir::Expr {
|
||||
id: DUMMY_NODE_ID,
|
||||
node: hir::ExprLit(P(Spanned { node: node, span: DUMMY_SP })),
|
||||
span: DUMMY_SP,
|
||||
attrs: ast::ThinVec::new(),
|
||||
})
|
||||
}
|
||||
|
||||
struct StaticInliner<'a, 'tcx: 'a> {
|
||||
tcx: TyCtxt<'a, 'tcx, 'tcx>,
|
||||
@ -588,505 +445,6 @@ impl<'a, 'tcx> StaticInliner<'a, 'tcx> {
|
||||
}
|
||||
}
|
||||
|
||||
/// 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: usize}
|
||||
/// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 }
|
||||
fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor,
|
||||
pats: Vec<&Pat>, left_ty: Ty<'tcx>) -> 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::TyTuple(..) => PatKind::Tuple(pats.collect(), None),
|
||||
|
||||
ty::TyAdt(adt, _) => {
|
||||
let v = ctor.variant_for_adt(adt);
|
||||
match v.ctor_kind {
|
||||
CtorKind::Fictive => {
|
||||
let field_pats: hir::HirVec<_> = v.fields.iter()
|
||||
.zip(pats)
|
||||
.filter(|&(_, ref pat)| pat.node != PatKind::Wild)
|
||||
.map(|(field, pat)| Spanned {
|
||||
span: DUMMY_SP,
|
||||
node: hir::FieldPat {
|
||||
name: field.name,
|
||||
pat: pat,
|
||||
is_shorthand: false,
|
||||
}
|
||||
}).collect();
|
||||
let has_more_fields = field_pats.len() < pats_len;
|
||||
PatKind::Struct(def_to_path(cx.tcx, v.did), field_pats, has_more_fields)
|
||||
}
|
||||
CtorKind::Fn => {
|
||||
PatKind::TupleStruct(def_to_path(cx.tcx, v.did), pats.collect(), None)
|
||||
}
|
||||
CtorKind::Const => {
|
||||
PatKind::Path(None, def_to_path(cx.tcx, v.did))
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
ty::TyRef(_, ty::TypeAndMut { mutbl, .. }) => {
|
||||
assert_eq!(pats_len, 1);
|
||||
PatKind::Ref(pats.nth(0).unwrap(), mutbl)
|
||||
}
|
||||
|
||||
ty::TySlice(_) => match ctor {
|
||||
&Slice(n) => {
|
||||
assert_eq!(pats_len, n);
|
||||
PatKind::Slice(pats.collect(), None, hir::HirVec::new())
|
||||
},
|
||||
_ => unreachable!()
|
||||
},
|
||||
|
||||
ty::TyArray(_, len) => {
|
||||
assert_eq!(pats_len, len);
|
||||
PatKind::Slice(pats.collect(), None, hir::HirVec::new())
|
||||
}
|
||||
|
||||
_ => {
|
||||
match *ctor {
|
||||
ConstantValue(ref v) => PatKind::Lit(const_val_to_expr(v)),
|
||||
_ => PatKind::Wild,
|
||||
}
|
||||
}
|
||||
};
|
||||
|
||||
P(hir::Pat {
|
||||
id: DUMMY_NODE_ID,
|
||||
node: pat,
|
||||
span: DUMMY_SP
|
||||
})
|
||||
}
|
||||
|
||||
impl Constructor {
|
||||
fn variant_for_adt<'tcx, 'container, 'a>(&self,
|
||||
adt: &'a ty::AdtDefData<'tcx, 'container>)
|
||||
-> &'a ty::VariantDefData<'tcx, 'container> {
|
||||
match self {
|
||||
&Variant(vid) => adt.variant_with_id(vid),
|
||||
_ => adt.struct_variant()
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn missing_constructors(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix,
|
||||
left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
|
||||
let used_constructors: Vec<Constructor> = rows.iter()
|
||||
.flat_map(|row| pat_constructors(cx, row[0], left_ty, max_slice_length))
|
||||
.collect();
|
||||
all_constructors(cx, left_ty, max_slice_length)
|
||||
.into_iter()
|
||||
.filter(|c| !used_constructors.contains(c))
|
||||
.collect()
|
||||
}
|
||||
|
||||
/// 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: usize) -> Vec<Constructor> {
|
||||
match left_ty.sty {
|
||||
ty::TyBool =>
|
||||
[true, false].iter().map(|b| ConstantValue(ConstVal::Bool(*b))).collect(),
|
||||
ty::TySlice(_) =>
|
||||
(0..max_slice_length+1).map(|length| Slice(length)).collect(),
|
||||
ty::TyAdt(def, _) if def.is_enum() =>
|
||||
def.variants.iter().map(|v| Variant(v.did)).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<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>,
|
||||
matrix: &Matrix<'a, 'tcx>,
|
||||
v: &[Pattern<'a, 'tcx>],
|
||||
witness: WitnessPreference)
|
||||
-> Usefulness {
|
||||
let &Matrix(ref rows) = matrix;
|
||||
debug!("is_useful({:?}, {:?})", matrix, v);
|
||||
if rows.is_empty() {
|
||||
return match witness {
|
||||
ConstructWitness => UsefulWithWitness(vec!()),
|
||||
LeaveOutWitness => Useful
|
||||
};
|
||||
}
|
||||
if rows[0].is_empty() {
|
||||
return NotUseful;
|
||||
}
|
||||
assert!(rows.iter().all(|r| r.len() == v.len()));
|
||||
let left_ty = match rows.iter().filter_map(|r| r[0].pattern_ty).next()
|
||||
.or_else(|| v[0].pattern_ty)
|
||||
{
|
||||
Some(ty) => ty,
|
||||
None => {
|
||||
// all patterns are wildcards - we can pick any type we want
|
||||
cx.tcx.types.bool
|
||||
}
|
||||
};
|
||||
|
||||
let max_slice_length = rows.iter().filter_map(|row| match row[0].pat.node {
|
||||
PatKind::Slice(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);
|
||||
debug!("is_useful - pat_constructors = {:?} left_ty = {:?}", constructors,
|
||||
left_ty);
|
||||
if constructors.is_empty() {
|
||||
let constructors = missing_constructors(cx, matrix, left_ty, max_slice_length);
|
||||
debug!("is_useful - missing_constructors = {:?}", constructors);
|
||||
if constructors.is_empty() {
|
||||
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)
|
||||
} else {
|
||||
let matrix = rows.iter().filter_map(|r| {
|
||||
match r[0].as_raw().node {
|
||||
PatKind::Binding(..) | PatKind::Wild => Some(r[1..].to_vec()),
|
||||
_ => None,
|
||||
}
|
||||
}).collect();
|
||||
match is_useful(cx, &matrix, &v[1..], witness) {
|
||||
UsefulWithWitness(pats) => {
|
||||
let mut new_pats: Vec<_> = constructors.into_iter().map(|constructor| {
|
||||
let arity = constructor_arity(cx, &constructor, left_ty);
|
||||
let wild_pats = vec![DUMMY_WILD_PAT; arity];
|
||||
construct_witness(cx, &constructor, wild_pats, left_ty)
|
||||
}).collect();
|
||||
new_pats.extend(pats);
|
||||
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<'a, 'tcx>(
|
||||
cx: &MatchCheckCtxt<'a, 'tcx>,
|
||||
&Matrix(ref m): &Matrix<'a, 'tcx>,
|
||||
v: &[Pattern<'a, 'tcx>],
|
||||
ctor: Constructor,
|
||||
lty: Ty<'tcx>,
|
||||
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: Pattern,
|
||||
left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> {
|
||||
let pat = p.as_raw();
|
||||
match pat.node {
|
||||
PatKind::Struct(..) | PatKind::TupleStruct(..) | PatKind::Path(..) =>
|
||||
match cx.tcx.expect_def(pat.id) {
|
||||
Def::Variant(id) | Def::VariantCtor(id, ..) => vec![Variant(id)],
|
||||
Def::Struct(..) | Def::StructCtor(..) | Def::Union(..) |
|
||||
Def::TyAlias(..) | Def::AssociatedTy(..) => vec![Single],
|
||||
Def::Const(..) | Def::AssociatedConst(..) =>
|
||||
span_bug!(p.span(), "const pattern should've been rewritten"),
|
||||
def => span_bug!(p.span(), "pat_constructors: unexpected definition {:?}", def),
|
||||
},
|
||||
PatKind::Lit(ref expr) =>
|
||||
vec![ConstantValue(eval_const_expr(cx.tcx, &expr))],
|
||||
PatKind::Range(ref lo, ref hi) =>
|
||||
vec![ConstantRange(eval_const_expr(cx.tcx, &lo), eval_const_expr(cx.tcx, &hi))],
|
||||
PatKind::Slice(ref before, ref slice, ref after) =>
|
||||
match left_ty.sty {
|
||||
ty::TyArray(..) => vec![Single],
|
||||
ty::TySlice(_) if slice.is_some() => {
|
||||
(before.len() + after.len()..max_slice_length+1)
|
||||
.map(|length| Slice(length))
|
||||
.collect()
|
||||
}
|
||||
ty::TySlice(_) => vec!(Slice(before.len() + after.len())),
|
||||
_ => span_bug!(pat.span, "pat_constructors: unexpected \
|
||||
slice pattern type {:?}", left_ty)
|
||||
},
|
||||
PatKind::Box(..) | PatKind::Tuple(..) | PatKind::Ref(..) =>
|
||||
vec![Single],
|
||||
PatKind::Binding(..) | PatKind::Wild =>
|
||||
vec![],
|
||||
}
|
||||
}
|
||||
|
||||
/// 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) -> usize {
|
||||
debug!("constructor_arity({:?}, {:?})", ctor, ty);
|
||||
match ty.sty {
|
||||
ty::TyTuple(ref fs) => fs.len(),
|
||||
ty::TyBox(_) => 1,
|
||||
ty::TySlice(_) => match *ctor {
|
||||
Slice(length) => length,
|
||||
ConstantValue(_) => {
|
||||
// TODO: this is utterly wrong, but required for byte arrays
|
||||
0
|
||||
}
|
||||
_ => bug!("bad slice pattern {:?} {:?}", ctor, ty)
|
||||
},
|
||||
ty::TyRef(..) => 1,
|
||||
ty::TyAdt(adt, _) => {
|
||||
ctor.variant_for_adt(adt).fields.len()
|
||||
}
|
||||
ty::TyArray(_, n) => n,
|
||||
_ => 0
|
||||
}
|
||||
}
|
||||
|
||||
fn range_covered_by_constructor(tcx: TyCtxt, span: Span,
|
||||
ctor: &Constructor,
|
||||
from: &ConstVal, to: &ConstVal)
|
||||
-> Result<bool, ErrorReported> {
|
||||
let (c_from, c_to) = match *ctor {
|
||||
ConstantValue(ref value) => (value, value),
|
||||
ConstantRange(ref from, ref to) => (from, to),
|
||||
Single => return Ok(true),
|
||||
_ => bug!()
|
||||
};
|
||||
let cmp_from = compare_const_vals(tcx, span, c_from, from)?;
|
||||
let cmp_to = compare_const_vals(tcx, span, c_to, to)?;
|
||||
Ok(cmp_from != Ordering::Less && cmp_to != Ordering::Greater)
|
||||
}
|
||||
|
||||
fn wrap_pat<'a, 'b, 'tcx>(cx: &MatchCheckCtxt<'b, 'tcx>,
|
||||
pat: &'a Pat)
|
||||
-> Pattern<'a, 'tcx>
|
||||
{
|
||||
let pat_ty = cx.tcx.pat_ty(pat);
|
||||
Pattern {
|
||||
pat: pat,
|
||||
pattern_ty: Some(match pat.node {
|
||||
PatKind::Binding(hir::BindByRef(..), ..) => {
|
||||
pat_ty.builtin_deref(false, ty::NoPreference).unwrap().ty
|
||||
}
|
||||
_ => pat_ty
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
/// 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, 'b, 'tcx>(
|
||||
cx: &MatchCheckCtxt<'b, 'tcx>,
|
||||
r: &[Pattern<'a, 'tcx>],
|
||||
constructor: &Constructor, col: usize, arity: usize)
|
||||
-> Option<Vec<Pattern<'a, 'tcx>>>
|
||||
{
|
||||
let pat = r[col].as_raw();
|
||||
let &Pat {
|
||||
id: pat_id, ref node, span: pat_span
|
||||
} = pat;
|
||||
let wpat = |pat: &'a Pat| wrap_pat(cx, pat);
|
||||
|
||||
let head: Option<Vec<Pattern>> = match *node {
|
||||
PatKind::Binding(..) | PatKind::Wild =>
|
||||
Some(vec![DUMMY_WILD_PATTERN; arity]),
|
||||
|
||||
PatKind::Path(..) => {
|
||||
match cx.tcx.expect_def(pat_id) {
|
||||
Def::Const(..) | Def::AssociatedConst(..) =>
|
||||
span_bug!(pat_span, "const pattern should've \
|
||||
been rewritten"),
|
||||
Def::VariantCtor(id, CtorKind::Const) if *constructor != Variant(id) => None,
|
||||
Def::VariantCtor(_, CtorKind::Const) |
|
||||
Def::StructCtor(_, CtorKind::Const) => Some(Vec::new()),
|
||||
def => span_bug!(pat_span, "specialize: unexpected definition: {:?}", def),
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::TupleStruct(_, ref args, ddpos) => {
|
||||
match cx.tcx.expect_def(pat_id) {
|
||||
Def::Const(..) | Def::AssociatedConst(..) =>
|
||||
span_bug!(pat_span, "const pattern should've \
|
||||
been rewritten"),
|
||||
Def::VariantCtor(id, CtorKind::Fn) if *constructor != Variant(id) => None,
|
||||
Def::VariantCtor(_, CtorKind::Fn) |
|
||||
Def::StructCtor(_, CtorKind::Fn) => {
|
||||
match ddpos {
|
||||
Some(ddpos) => {
|
||||
let mut pats: Vec<_> = args[..ddpos].iter().map(|p| {
|
||||
wpat(p)
|
||||
}).collect();
|
||||
pats.extend(repeat(DUMMY_WILD_PATTERN).take(arity - args.len()));
|
||||
pats.extend(args[ddpos..].iter().map(|p| wpat(p)));
|
||||
Some(pats)
|
||||
}
|
||||
None => Some(args.iter().map(|p| wpat(p)).collect())
|
||||
}
|
||||
}
|
||||
def => span_bug!(pat_span, "specialize: unexpected definition: {:?}", def),
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Struct(_, ref pattern_fields, _) => {
|
||||
let adt = cx.tcx.node_id_to_type(pat_id).ty_adt_def().unwrap();
|
||||
let variant = constructor.variant_for_adt(adt);
|
||||
let def_variant = adt.variant_of_def(cx.tcx.expect_def(pat_id));
|
||||
if variant.did == def_variant.did {
|
||||
Some(variant.fields.iter().map(|sf| {
|
||||
match pattern_fields.iter().find(|f| f.node.name == sf.name) {
|
||||
Some(ref f) => wpat(&f.node.pat),
|
||||
_ => DUMMY_WILD_PATTERN
|
||||
}
|
||||
}).collect())
|
||||
} else {
|
||||
None
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Tuple(ref args, Some(ddpos)) => {
|
||||
let mut pats: Vec<_> = args[..ddpos].iter().map(|p| wpat(p)).collect();
|
||||
pats.extend(repeat(DUMMY_WILD_PATTERN).take(arity - args.len()));
|
||||
pats.extend(args[ddpos..].iter().map(|p| wpat(p)));
|
||||
Some(pats)
|
||||
}
|
||||
PatKind::Tuple(ref args, None) =>
|
||||
Some(args.iter().map(|p| wpat(&**p)).collect()),
|
||||
|
||||
PatKind::Box(ref inner) | PatKind::Ref(ref inner, _) =>
|
||||
Some(vec![wpat(&**inner)]),
|
||||
|
||||
PatKind::Lit(ref expr) => {
|
||||
match r[col].pattern_ty {
|
||||
Some(&ty::TyS { sty: ty::TyRef(_, mt), .. }) => {
|
||||
// HACK: handle string literals. A string literal pattern
|
||||
// serves both as an unary reference pattern and as a
|
||||
// nullary value pattern, depending on the type.
|
||||
Some(vec![Pattern {
|
||||
pat: pat,
|
||||
pattern_ty: Some(mt.ty)
|
||||
}])
|
||||
}
|
||||
Some(ty) => {
|
||||
assert_eq!(constructor_arity(cx, constructor, ty), 0);
|
||||
let expr_value = eval_const_expr(cx.tcx, &expr);
|
||||
match range_covered_by_constructor(
|
||||
cx.tcx, expr.span, constructor, &expr_value, &expr_value
|
||||
) {
|
||||
Ok(true) => Some(vec![]),
|
||||
Ok(false) => None,
|
||||
Err(ErrorReported) => None,
|
||||
}
|
||||
}
|
||||
None => span_bug!(pat.span, "literal pattern {:?} has no type", pat)
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Range(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(
|
||||
cx.tcx, pat_span, constructor, &from_value, &to_value
|
||||
) {
|
||||
Ok(true) => Some(vec![]),
|
||||
Ok(false) => None,
|
||||
Err(ErrorReported) => None,
|
||||
}
|
||||
}
|
||||
|
||||
PatKind::Slice(ref before, ref slice, ref after) => {
|
||||
let pat_len = before.len() + after.len();
|
||||
match *constructor {
|
||||
Single => {
|
||||
// Fixed-length vectors.
|
||||
Some(
|
||||
before.iter().map(|p| wpat(p)).chain(
|
||||
repeat(DUMMY_WILD_PATTERN).take(arity - pat_len).chain(
|
||||
after.iter().map(|p| wpat(p))
|
||||
)).collect())
|
||||
},
|
||||
Slice(length) if pat_len <= length && slice.is_some() => {
|
||||
Some(
|
||||
before.iter().map(|p| wpat(p)).chain(
|
||||
repeat(DUMMY_WILD_PATTERN).take(arity - pat_len).chain(
|
||||
after.iter().map(|p| wpat(p))
|
||||
)).collect())
|
||||
}
|
||||
Slice(length) if pat_len == length => {
|
||||
Some(
|
||||
before.iter().map(|p| wpat(p)).chain(
|
||||
after.iter().map(|p| wpat(p))
|
||||
).collect())
|
||||
}
|
||||
_ => None
|
||||
}
|
||||
}
|
||||
};
|
||||
debug!("specialize({:?}, {:?}) = {:?}", r[col], arity, head);
|
||||
|
||||
head.map(|mut head| {
|
||||
head.extend_from_slice(&r[..col]);
|
||||
head.extend_from_slice(&r[col + 1..]);
|
||||
head
|
||||
})
|
||||
}
|
||||
|
||||
fn check_local(cx: &mut MatchCheckCtxt, loc: &hir::Local) {
|
||||
intravisit::walk_local(cx, loc);
|
||||
|
||||
@ -1103,7 +461,7 @@ fn check_fn(cx: &mut MatchCheckCtxt,
|
||||
decl: &hir::FnDecl,
|
||||
body: &hir::Block,
|
||||
sp: Span,
|
||||
fn_id: NodeId) {
|
||||
fn_id: ast::NodeId) {
|
||||
match kind {
|
||||
FnKind::Closure(_) => {}
|
||||
_ => cx.param_env = ty::ParameterEnvironment::for_item(cx.tcx, fn_id),
|
||||
@ -1135,17 +493,6 @@ fn check_irrefutable(cx: &MatchCheckCtxt, pat: &Pat, is_fn_arg: bool) {
|
||||
});
|
||||
}
|
||||
|
||||
fn is_refutable<A, F>(cx: &MatchCheckCtxt, pat: &Pat, refutable: F) -> Option<A> where
|
||||
F: FnOnce(&Pat) -> A,
|
||||
{
|
||||
let pats = Matrix(vec!(vec!(wrap_pat(cx, pat))));
|
||||
match is_useful(cx, &pats, &[DUMMY_WILD_PATTERN], ConstructWitness) {
|
||||
UsefulWithWitness(pats) => Some(refutable(&pats[0])),
|
||||
NotUseful => None,
|
||||
Useful => bug!()
|
||||
}
|
||||
}
|
||||
|
||||
// Legality of move bindings checking
|
||||
fn check_legality_of_move_bindings(cx: &MatchCheckCtxt,
|
||||
has_guard: bool,
|
||||
@ -1219,10 +566,10 @@ struct MutationChecker<'a, 'gcx: 'a> {
|
||||
|
||||
impl<'a, 'gcx, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'gcx> {
|
||||
fn matched_pat(&mut self, _: &Pat, _: cmt, _: euv::MatchMode) {}
|
||||
fn consume(&mut self, _: NodeId, _: Span, _: cmt, _: ConsumeMode) {}
|
||||
fn consume(&mut self, _: ast::NodeId, _: Span, _: cmt, _: ConsumeMode) {}
|
||||
fn consume_pat(&mut self, _: &Pat, _: cmt, _: ConsumeMode) {}
|
||||
fn borrow(&mut self,
|
||||
_: NodeId,
|
||||
_: ast::NodeId,
|
||||
span: Span,
|
||||
_: cmt,
|
||||
_: &'tcx ty::Region,
|
||||
@ -1238,8 +585,8 @@ impl<'a, 'gcx, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'gcx> {
|
||||
ty::ImmBorrow | ty::UniqueImmBorrow => {}
|
||||
}
|
||||
}
|
||||
fn decl_without_init(&mut self, _: NodeId, _: Span) {}
|
||||
fn mutate(&mut self, _: NodeId, span: Span, _: cmt, mode: MutateMode) {
|
||||
fn decl_without_init(&mut self, _: ast::NodeId, _: Span) {}
|
||||
fn mutate(&mut self, _: ast::NodeId, span: Span, _: cmt, mode: MutateMode) {
|
||||
match mode {
|
||||
MutateMode::JustWrite | MutateMode::WriteAndRead => {
|
||||
struct_span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard")
|
||||
|
||||
@ -40,7 +40,7 @@ Ensure the ordering of the match arm is correct and remove any superfluous
|
||||
arms.
|
||||
"##,
|
||||
|
||||
E0002: r##"
|
||||
/*E0002: r##"
|
||||
This error indicates that an empty match expression is invalid because the type
|
||||
it is matching on is non-empty (there exist values of this type). In safe code
|
||||
it is impossible to create an instance of an empty type, so empty match
|
||||
@ -68,7 +68,7 @@ fn foo(x: Option<String>) {
|
||||
}
|
||||
}
|
||||
```
|
||||
"##,
|
||||
"##,*/
|
||||
|
||||
|
||||
E0003: r##"
|
||||
|
||||
@ -47,6 +47,7 @@ extern crate serialize as rustc_serialize; // used by deriving
|
||||
pub mod diagnostics;
|
||||
|
||||
mod eval;
|
||||
mod _match;
|
||||
pub mod check_match;
|
||||
pub mod pattern;
|
||||
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user