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auto merge of #14444 : huonw/rust/nice-for-errors, r=alexcrichton 

Change `for` desugaring & make refutable pattern errors more precise

This changes for to desugar to the `let`-based pattern match as described in #14390, and adjusts the compiler to use this information for error messages that even mention that it's in a `for` loop.

Also, it makes the compiler record the exact positions of refutable parts of a pattern, to point to exactly them in error messages.
This commit is contained in:
bors 2014-05-27 14:36:40 -07:00
parent 1e2bb09bbb 0df221e993
commit 1fc29ef0c8
8 changed files with 140 additions and 28 deletions
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65
src/librustc/middle/check_match.rs
View File

@ -863,9 +863,18 @@ fn default(cx: &MatchCheckCtxt, r: &[@Pat]) -> Option<Vec<@Pat> > {
fn check_local(cx: &mut MatchCheckCtxt, loc: &Local) {
visit::walk_local(cx, loc, ());
if is_refutable(cx, loc.pat) {
cx.tcx.sess.span_err(loc.pat.span,
"refutable pattern in local binding");
let name = match loc.source {
LocalLet => "local",
LocalFor => "`for` loop"
};
let mut spans = vec![];
find_refutable(cx, loc.pat, &mut spans);
for span in spans.iter() {
cx.tcx.sess.span_err(*span,
format!("refutable pattern in {} binding", name).as_slice());
}
// Check legality of move bindings.
@ -879,53 +888,65 @@ fn check_fn(cx: &mut MatchCheckCtxt,
sp: Span) {
visit::walk_fn(cx, kind, decl, body, sp, ());
for input in decl.inputs.iter() {
if is_refutable(cx, input.pat) {
cx.tcx.sess.span_err(input.pat.span,
let mut spans = vec![];
find_refutable(cx, input.pat, &mut spans);
for span in spans.iter() {
cx.tcx.sess.span_err(*span,
"refutable pattern in function argument");
}
}
}
fn is_refutable(cx: &MatchCheckCtxt, pat: &Pat) -> bool {
fn find_refutable(cx: &MatchCheckCtxt, pat: &Pat, spans: &mut Vec<Span>) {
macro_rules! this_pattern {
() => {
{
spans.push(pat.span);
return
}
}
}
let opt_def = cx.tcx.def_map.borrow().find_copy(&pat.id);
match opt_def {
Some(DefVariant(enum_id, _, _)) => {
if ty::enum_variants(cx.tcx, enum_id).len() != 1u {
return true;
this_pattern!()
}
}
Some(DefStatic(..)) => return true,
Some(DefStatic(..)) => this_pattern!(),
_ => ()
}
match pat.node {
PatUniq(sub) | PatRegion(sub) | PatIdent(_, _, Some(sub)) => {
is_refutable(cx, sub)
find_refutable(cx, sub, spans)
}
PatWild | PatWildMulti | PatIdent(_, _, None) => { false }
PatWild | PatWildMulti | PatIdent(_, _, None) => {}
PatLit(lit) => {
match lit.node {
ExprLit(lit) => {
match lit.node {
LitNil => false, // `()`
_ => true,
LitNil => {} // `()`
_ => this_pattern!(),
}
}
_ => true,
_ => this_pattern!(),
}
}
PatRange(_, _) => { true }
PatRange(_, _) => { this_pattern!() }
PatStruct(_, ref fields, _) => {
fields.iter().any(|f| is_refutable(cx, f.pat))
for f in fields.iter() {
find_refutable(cx, f.pat, spans);
}
}
PatTup(ref elts) => {
elts.iter().any(|elt| is_refutable(cx, *elt))
PatTup(ref elts) | PatEnum(_, Some(ref elts))=> {
for elt in elts.iter() {
find_refutable(cx, *elt, spans)
}
}
PatEnum(_, Some(ref args)) => {
args.iter().any(|a| is_refutable(cx, *a))
}
PatEnum(_,_) => { false }
PatVec(..) => { true }
PatEnum(_,_) => {}
PatVec(..) => { this_pattern!() }
}
}

9
src/libsyntax/ast.rs
View File

@ -417,6 +417,14 @@ pub enum Stmt_ {
StmtMac(Mac, bool),
}
/// Where a local declaration came from: either a true `let ... =
/// ...;`, or one desugared from the pattern of a for loop.
#[deriving(Clone, Eq, TotalEq, Encodable, Decodable, Hash)]
pub enum LocalSource {
LocalLet,
LocalFor,
}
// FIXME (pending discussion of #1697, #2178...): local should really be
// a refinement on pat.
/// Local represents a `let` statement, e.g., `let <pat>:<ty> = <expr>;`
@ -427,6 +435,7 @@ pub struct Local {
pub init: Option<@Expr>,
pub id: NodeId,
pub span: Span,
pub source: LocalSource,
}
pub type Decl = Spanned<Decl_>;

2
src/libsyntax/ext/build.rs
View File

@ -439,6 +439,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
init: Some(ex),
id: ast::DUMMY_NODE_ID,
span: sp,
source: ast::LocalLet,
};
let decl = respan(sp, ast::DeclLocal(local));
@respan(sp, ast::StmtDecl(@decl, ast::DUMMY_NODE_ID))
@ -462,6 +463,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
init: Some(ex),
id: ast::DUMMY_NODE_ID,
span: sp,
source: ast::LocalLet,
};
let decl = respan(sp, ast::DeclLocal(local));
@respan(sp, ast::StmtDecl(@decl, ast::DUMMY_NODE_ID))

40
src/libsyntax/ext/expand.rs
View File

@ -147,11 +147,17 @@ pub fn expand_expr(e: @ast::Expr, fld: &mut MacroExpander) -> @ast::Expr {
// ['<ident>:] loop {
// match i.next() {
// None => break,
// Some(<src_pat>) => <src_loop_block>
// Some(mut value) => {
// let <src_pat> = value;
// <src_loop_block>
// }
// }
// }
// }
// }
//
// (The use of the `let` is to give better error messages
// when the pattern is refutable.)
let local_ident = token::gensym_ident("__i"); // FIXME #13573
let next_ident = fld.cx.ident_of("next");
@ -167,11 +173,33 @@ pub fn expand_expr(e: @ast::Expr, fld: &mut MacroExpander) -> @ast::Expr {
fld.cx.arm(span, vec!(none_pat), break_expr)
};
// `Some(<src_pat>) => <src_loop_block>`
// let <src_pat> = value;
let value_ident = token::gensym_ident("__value");
// this is careful to use src_pat.span so that error
// messages point exact at that.
let local = @ast::Local {
ty: fld.cx.ty_infer(src_pat.span),
pat: src_pat,
init: Some(fld.cx.expr_ident(src_pat.span, value_ident)),
id: ast::DUMMY_NODE_ID,
span: src_pat.span,
source: ast::LocalFor
};
let local = codemap::respan(src_pat.span, ast::DeclLocal(local));
let local = @codemap::respan(span, ast::StmtDecl(@local, ast::DUMMY_NODE_ID));
// { let ...; <src_loop_block> }
let block = fld.cx.block(span, vec![local],
Some(fld.cx.expr_block(src_loop_block)));
// `Some(mut value) => { ... }`
// Note the _'s in the name will stop any unused mutability warnings.
let value_pat = fld.cx.pat_ident_binding_mode(span, value_ident,
ast::BindByValue(ast::MutMutable));
let some_arm =
fld.cx.arm(span,
vec!(fld.cx.pat_enum(span, some_path, vec!(src_pat))),
fld.cx.expr_block(src_loop_block));
vec!(fld.cx.pat_enum(span, some_path, vec!(value_pat))),
fld.cx.expr_block(block));
// `match i.next() { ... }`
let match_expr = {
@ -669,7 +697,8 @@ fn expand_non_macro_stmt(s: &Stmt, fld: &mut MacroExpander)
pat: pat,
init: init,
id: id,
span: span
span: span,
source: source,
} = **local;
// expand the pat (it might contain exprs... #:(o)>
let expanded_pat = fld.fold_pat(pat);
@ -703,6 +732,7 @@ fn expand_non_macro_stmt(s: &Stmt, fld: &mut MacroExpander)
init: new_init_opt,
id: id,
span: span,
source: source
};
SmallVector::one(@Spanned {
node: StmtDecl(@Spanned {

1
src/libsyntax/fold.rs
View File

@ -288,6 +288,7 @@ pub trait Folder {
pat: self.fold_pat(l.pat),
init: l.init.map(|e| self.fold_expr(e)),
span: self.new_span(l.span),
source: l.source,
}
}

3
src/libsyntax/parse/parser.rs
View File

@ -34,7 +34,7 @@ use ast::{Ident, NormalFn, Inherited, Item, Item_, ItemStatic};
use ast::{ItemEnum, ItemFn, ItemForeignMod, ItemImpl};
use ast::{ItemMac, ItemMod, ItemStruct, ItemTrait, ItemTy, Lit, Lit_};
use ast::{LitBool, LitFloat, LitFloatUnsuffixed, LitInt, LitChar};
use ast::{LitIntUnsuffixed, LitNil, LitStr, LitUint, Local};
use ast::{LitIntUnsuffixed, LitNil, LitStr, LitUint, Local, LocalLet};
use ast::{MutImmutable, MutMutable, Mac_, MacInvocTT, Matcher, MatchNonterminal};
use ast::{MatchSeq, MatchTok, Method, MutTy, BiMul, Mutability};
use ast::{NamedField, UnNeg, NoReturn, UnNot, P, Pat, PatEnum};
@ -3034,6 +3034,7 @@ impl<'a> Parser<'a> {
init: init,
id: ast::DUMMY_NODE_ID,
span: mk_sp(lo, self.last_span.hi),
source: LocalLet,
}
}

16
src/test/compile-fail/for-loop-refutable-pattern-error-message.rs Normal file
View File

@ -0,0 +1,16 @@
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
fn main() {
for
&1 //~ ERROR refutable pattern in `for` loop binding
in [1].iter() {}
}

32
src/test/compile-fail/precise-refutable-pattern-errors.rs Normal file
View File

@ -0,0 +1,32 @@
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
fn func(
(
1, //~ ERROR refutable pattern in function argument
(
Some( //~ ERROR refutable pattern in function argument
1), // nested, so no warning.
2..3 //~ ERROR refutable pattern in function argument
)
): (int, (Option<int>, int))
) {}
fn main() {
let (
1, //~ ERROR refutable pattern in local binding
(
Some( //~ ERROR refutable pattern in local binding
1), // nested, so no warning.
2..3 //~ ERROR refutable pattern in local binding
)
) = (1, (None, 2));
}