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Rollup merge of #48500 - petrochenkov:parpat, r=nikomatsakis

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Support parentheses in patterns under feature gate

This is a prerequisite for any other extensions to pattern syntax - `|` with multiple patterns, type ascription, `..PAT` in slice patterns.

Closes https://github.com/rust-lang/rfcs/issues/554
This commit is contained in:
Manish Goregaokar 2018-02-28 23:33:30 -08:00
commit 38f4d557d0
12 changed files with 166 additions and 107 deletions
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154
src/librustc/hir/lowering.rs
View File

@ -2472,86 +2472,88 @@ impl<'a> LoweringContext<'a> {
}
fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
let LoweredNodeId { node_id, hir_id } = self.lower_node_id(p.id);
let node = match p.node {
PatKind::Wild => hir::PatKind::Wild,
PatKind::Ident(ref binding_mode, pth1, ref sub) => {
match self.resolver.get_resolution(p.id).map(|d| d.base_def()) {
// `None` can occur in body-less function signatures
def @ None | def @ Some(Def::Local(_)) => {
let canonical_id = match def {
Some(Def::Local(id)) => id,
_ => p.id
};
hir::PatKind::Binding(self.lower_binding_mode(binding_mode),
canonical_id,
respan(pth1.span, pth1.node.name),
sub.as_ref().map(|x| self.lower_pat(x)))
}
Some(def) => {
hir::PatKind::Path(hir::QPath::Resolved(None, P(hir::Path {
span: pth1.span,
def,
segments: hir_vec![
hir::PathSegment::from_name(pth1.node.name)
],
})))
}
}
}
PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
PatKind::TupleStruct(ref path, ref pats, ddpos) => {
let qpath = self.lower_qpath(p.id, &None, path, ParamMode::Optional,
ImplTraitContext::Disallowed);
hir::PatKind::TupleStruct(qpath,
pats.iter().map(|x| self.lower_pat(x)).collect(),
ddpos)
}
PatKind::Path(ref qself, ref path) => {
hir::PatKind::Path(self.lower_qpath(p.id, qself, path, ParamMode::Optional,
ImplTraitContext::Disallowed))
}
PatKind::Struct(ref path, ref fields, etc) => {
let qpath = self.lower_qpath(p.id, &None, path, ParamMode::Optional,
ImplTraitContext::Disallowed);
let fs = fields.iter()
.map(|f| {
Spanned {
span: f.span,
node: hir::FieldPat {
name: self.lower_ident(f.node.ident),
pat: self.lower_pat(&f.node.pat),
is_shorthand: f.node.is_shorthand,
},
}
})
.collect();
hir::PatKind::Struct(qpath, fs, etc)
}
PatKind::Tuple(ref elts, ddpos) => {
hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
}
PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
PatKind::Ref(ref inner, mutbl) => {
hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
}
PatKind::Range(ref e1, ref e2, ref end) => {
hir::PatKind::Range(P(self.lower_expr(e1)),
P(self.lower_expr(e2)),
self.lower_range_end(end))
}
PatKind::Slice(ref before, ref slice, ref after) => {
hir::PatKind::Slice(before.iter().map(|x| self.lower_pat(x)).collect(),
slice.as_ref().map(|x| self.lower_pat(x)),
after.iter().map(|x| self.lower_pat(x)).collect())
}
PatKind::Paren(ref inner) => return self.lower_pat(inner),
PatKind::Mac(_) => panic!("Shouldn't exist here"),
};
let LoweredNodeId { node_id, hir_id } = self.lower_node_id(p.id);
P(hir::Pat {
id: node_id,
hir_id,
node: match p.node {
PatKind::Wild => hir::PatKind::Wild,
PatKind::Ident(ref binding_mode, pth1, ref sub) => {
match self.resolver.get_resolution(p.id).map(|d| d.base_def()) {
// `None` can occur in body-less function signatures
def @ None | def @ Some(Def::Local(_)) => {
let canonical_id = match def {
Some(Def::Local(id)) => id,
_ => p.id
};
hir::PatKind::Binding(self.lower_binding_mode(binding_mode),
canonical_id,
respan(pth1.span, pth1.node.name),
sub.as_ref().map(|x| self.lower_pat(x)))
}
Some(def) => {
hir::PatKind::Path(hir::QPath::Resolved(None, P(hir::Path {
span: pth1.span,
def,
segments: hir_vec![
hir::PathSegment::from_name(pth1.node.name)
],
})))
}
}
}
PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
PatKind::TupleStruct(ref path, ref pats, ddpos) => {
let qpath = self.lower_qpath(p.id, &None, path, ParamMode::Optional,
ImplTraitContext::Disallowed);
hir::PatKind::TupleStruct(qpath,
pats.iter().map(|x| self.lower_pat(x)).collect(),
ddpos)
}
PatKind::Path(ref qself, ref path) => {
hir::PatKind::Path(self.lower_qpath(p.id, qself, path, ParamMode::Optional,
ImplTraitContext::Disallowed))
}
PatKind::Struct(ref path, ref fields, etc) => {
let qpath = self.lower_qpath(p.id, &None, path, ParamMode::Optional,
ImplTraitContext::Disallowed);
let fs = fields.iter()
.map(|f| {
Spanned {
span: f.span,
node: hir::FieldPat {
name: self.lower_ident(f.node.ident),
pat: self.lower_pat(&f.node.pat),
is_shorthand: f.node.is_shorthand,
},
}
})
.collect();
hir::PatKind::Struct(qpath, fs, etc)
}
PatKind::Tuple(ref elts, ddpos) => {
hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
}
PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
PatKind::Ref(ref inner, mutbl) => {
hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
}
PatKind::Range(ref e1, ref e2, ref end) => {
hir::PatKind::Range(P(self.lower_expr(e1)),
P(self.lower_expr(e2)),
self.lower_range_end(end))
}
PatKind::Slice(ref before, ref slice, ref after) => {
hir::PatKind::Slice(before.iter().map(|x| self.lower_pat(x)).collect(),
slice.as_ref().map(|x| self.lower_pat(x)),
after.iter().map(|x| self.lower_pat(x)).collect())
}
PatKind::Mac(_) => panic!("Shouldn't exist here"),
},
node,
span: p.span,
})
}

1
src/librustc_lint/builtin.rs
View File

@ -737,6 +737,7 @@ impl EarlyLintPass for IllegalFloatLiteralPattern {
PatKind::TupleStruct(..) |
PatKind::Ref(..) |
PatKind::Box(..) |
PatKind::Paren(..) |
PatKind::Slice(..) => (),
// Extract the expressions and check them

4
src/libsyntax/ast.rs
View File

@ -562,7 +562,7 @@ impl Pat {
PatKind::TupleStruct(_, ref s, _) | PatKind::Tuple(ref s, _) => {
s.iter().all(|p| p.walk(it))
}
PatKind::Box(ref s) | PatKind::Ref(ref s, _) => {
PatKind::Box(ref s) | PatKind::Ref(ref s, _) | PatKind::Paren(ref s) => {
s.walk(it)
}
PatKind::Slice(ref before, ref slice, ref after) => {
@ -656,6 +656,8 @@ pub enum PatKind {
/// `[a, b, ..i, y, z]` is represented as:
/// `PatKind::Slice(box [a, b], Some(i), box [y, z])`
Slice(Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>),
/// Parentheses in patters used for grouping, i.e. `(PAT)`.
Paren(P<Pat>),
/// A macro pattern; pre-expansion
Mac(Mac),
}

7
src/libsyntax/feature_gate.rs
View File

@ -449,6 +449,9 @@ declare_features! (
// Multiple patterns with `|` in `if let` and `while let`
(active, if_while_or_patterns, "1.26.0", Some(48215)),
// Parentheses in patterns
(active, pattern_parentheses, "1.26.0", None),
);
declare_features! (
@ -1663,6 +1666,10 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
gate_feature_post!(&self, dotdoteq_in_patterns, pattern.span,
"`..=` syntax in patterns is experimental");
}
PatKind::Paren(..) => {
gate_feature_post!(&self, pattern_parentheses, pattern.span,
"parentheses in patterns are unstable");
}
_ => {}
}
visit::walk_pat(self, pattern)

1
src/libsyntax/fold.rs
View File

@ -1148,6 +1148,7 @@ pub fn noop_fold_pat<T: Folder>(p: P<Pat>, folder: &mut T) -> P<Pat> {
slice.map(|x| folder.fold_pat(x)),
after.move_map(|x| folder.fold_pat(x)))
}
PatKind::Paren(inner) => PatKind::Paren(folder.fold_pat(inner)),
PatKind::Mac(mac) => PatKind::Mac(folder.fold_mac(mac))
},
span: folder.new_span(span)

66
src/libsyntax/parse/parser.rs
View File

@ -3484,33 +3484,47 @@ impl<'a> Parser<'a> {
};
}
fn parse_pat_tuple_elements(&mut self, unary_needs_comma: bool)
-> PResult<'a, (Vec<P<Pat>>, Option<usize>)> {
let mut fields = vec![];
let mut ddpos = None;
// Parses a parenthesized list of patterns like
// `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
// - a vector of the patterns that were parsed
// - an option indicating the index of the `..` element
// - a boolean indicating whether a trailing comma was present.
// Trailing commas are significant because (p) and (p,) are different patterns.
fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
self.expect(&token::OpenDelim(token::Paren))?;
while !self.check(&token::CloseDelim(token::Paren)) {
if ddpos.is_none() && self.eat(&token::DotDot) {
ddpos = Some(fields.len());
if self.eat(&token::Comma) {
// `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
fields.push(self.parse_pat()?);
let mut fields = Vec::new();
let mut ddpos = None;
let mut trailing_comma = false;
loop {
if self.eat(&token::DotDot) {
if ddpos.is_none() {
ddpos = Some(fields.len());
} else {
// Emit a friendly error, ignore `..` and continue parsing
self.span_err(self.prev_span,
"`..` can only be used once per tuple or tuple struct pattern");
}
} else if ddpos.is_some() && self.eat(&token::DotDot) {
// Emit a friendly error, ignore `..` and continue parsing
self.span_err(self.prev_span, "`..` can only be used once per \
tuple or tuple struct pattern");
} else {
} else if !self.check(&token::CloseDelim(token::Paren)) {
fields.push(self.parse_pat()?);
} else {
break
}
if !self.check(&token::CloseDelim(token::Paren)) ||
(unary_needs_comma && fields.len() == 1 && ddpos.is_none()) {
self.expect(&token::Comma)?;
trailing_comma = self.eat(&token::Comma);
if !trailing_comma {
break
}
}
Ok((fields, ddpos))
if ddpos == Some(fields.len()) && trailing_comma {
// `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
self.span_err(self.prev_span, "trailing comma is not permitted after `..`");
}
self.expect(&token::CloseDelim(token::Paren))?;
Ok((fields, ddpos, trailing_comma))
}
fn parse_pat_vec_elements(
@ -3714,10 +3728,12 @@ impl<'a> Parser<'a> {
}
token::OpenDelim(token::Paren) => {
// Parse (pat,pat,pat,...) as tuple pattern
self.bump();
let (fields, ddpos) = self.parse_pat_tuple_elements(true)?;
self.expect(&token::CloseDelim(token::Paren))?;
pat = PatKind::Tuple(fields, ddpos);
let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
PatKind::Paren(fields.into_iter().nth(0).unwrap())
} else {
PatKind::Tuple(fields, ddpos)
};
}
token::OpenDelim(token::Bracket) => {
// Parse [pat,pat,...] as slice pattern
@ -3807,9 +3823,7 @@ impl<'a> Parser<'a> {
return Err(self.fatal("unexpected `(` after qualified path"));
}
// Parse tuple struct or enum pattern
self.bump();
let (fields, ddpos) = self.parse_pat_tuple_elements(false)?;
self.expect(&token::CloseDelim(token::Paren))?;
let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
pat = PatKind::TupleStruct(path, fields, ddpos)
}
_ => pat = PatKind::Path(qself, path),

5
src/libsyntax/print/pprust.rs
View File

@ -2659,6 +2659,11 @@ impl<'a> State<'a> {
|s, p| s.print_pat(p))?;
self.s.word("]")?;
}
PatKind::Paren(ref inner) => {
self.popen()?;
self.print_pat(inner)?;
self.pclose()?;
}
PatKind::Mac(ref m) => self.print_mac(m, token::Paren)?,
}
self.ann.post(self, NodePat(pat))

3
src/libsyntax/visit.rs
View File

@ -425,7 +425,8 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
walk_list!(visitor, visit_pat, tuple_elements);
}
PatKind::Box(ref subpattern) |
PatKind::Ref(ref subpattern, _) => {
PatKind::Ref(ref subpattern, _) |
PatKind::Paren(ref subpattern) => {
visitor.visit_pat(subpattern)
}
PatKind::Ident(_, ref pth1, ref optional_subpattern) => {

2
src/test/parse-fail/pat-tuple-2.rs
View File

@ -12,6 +12,6 @@
fn main() {
match 0 {
(pat, ..,) => {} //~ ERROR expected pattern, found `)`
(pat, ..,) => {} //~ ERROR trailing comma is not permitted after `..`
}
}

4
src/test/parse-fail/pat-tuple-6.rs → src/test/run-pass/pat-tuple-7.rs
View File

@ -8,10 +8,10 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: -Z parse-only
#![feature(pattern_parentheses)]
fn main() {
match 0 {
(pat) => {} //~ ERROR expected one of `,` or `@`, found `)`
(pat) => assert_eq!(pat, 0)
}
}

15
src/test/ui/feature-gate-pattern_parentheses.rs Normal file
View File

@ -0,0 +1,15 @@
// Copyright 2017 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() {
match 0 {
(pat) => {} //~ ERROR parentheses in patterns are unstable
}
}

11
src/test/ui/feature-gate-pattern_parentheses.stderr Normal file
View File

@ -0,0 +1,11 @@
error[E0658]: parentheses in patterns are unstable
--> $DIR/feature-gate-pattern_parentheses.rs:13:9
|
LL | (pat) => {} //~ ERROR parentheses in patterns are unstable
| ^^^^^
|
= help: add #![feature(pattern_parentheses)] to the crate attributes to enable
error: aborting due to previous error
If you want more information on this error, try using "rustc --explain E0658"