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Implement half-open range patterns #753

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merged 1 commit into from
Jan 26, 2020
Merged

Implement half-open range patterns #753

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2 changes: 1 addition & 1 deletion src/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1948,7 +1948,7 @@ pub(crate) mod parsing {
return parse_expr(input, expr, allow_struct, Precedence::Any);
};

if input.peek(Token![.]) || input.peek(Token![?]) {
if input.peek(Token![.]) && !input.peek(Token![..]) || input.peek(Token![?]) {
expr = trailer_helper(input, expr)?;

attrs.extend(expr.replace_attrs(Vec::new()));
Expand Down
101 changes: 70 additions & 31 deletions src/pat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -386,11 +386,12 @@ mod parsing {
use super::*;

use crate::ext::IdentExt;
use crate::parse::{Parse, ParseStream, Result};
use crate::parse::{Parse, ParseBuffer, ParseStream, Result};
use crate::path;

impl Parse for Pat {
fn parse(input: ParseStream) -> Result<Self> {
let begin = input.fork();
let lookahead = input.lookahead1();
if lookahead.peek(Ident)
&& ({
Expand Down Expand Up @@ -434,18 +435,19 @@ mod parsing {
} else if lookahead.peek(token::Bracket) {
input.call(pat_slice).map(Pat::Slice)
} else if lookahead.peek(Token![..]) && !input.peek(Token![...]) {
input.call(pat_rest).map(Pat::Rest)
pat_range_half_open(input, begin)
} else {
Err(lookahead.error())
}
}
}

fn pat_path_or_macro_or_struct_or_range(input: ParseStream) -> Result<Pat> {
let begin = input.fork();
let (qself, path) = path::parsing::qpath(input, true)?;

if input.peek(Token![..]) {
return pat_range(input, qself, path).map(Pat::Range);
return pat_range(input, begin, qself, path);
}

if qself.is_some() {
Expand Down Expand Up @@ -487,7 +489,7 @@ mod parsing {
} else if input.peek(token::Paren) {
pat_tuple_struct(input, path).map(Pat::TupleStruct)
} else if input.peek(Token![..]) {
pat_range(input, qself, path).map(Pat::Range)
pat_range(input, begin, qself, path)
} else {
Ok(Pat::Path(PatPath {
attrs: Vec::new(),
Expand Down Expand Up @@ -624,17 +626,44 @@ mod parsing {
})
}

fn pat_range(input: ParseStream, qself: Option<QSelf>, path: Path) -> Result<PatRange> {
Ok(PatRange {
attrs: Vec::new(),
lo: Box::new(Expr::Path(ExprPath {
fn pat_range(
input: ParseStream,
begin: ParseBuffer,
qself: Option<QSelf>,
path: Path,
) -> Result<Pat> {
let limits: RangeLimits = input.parse()?;
let hi = input.call(pat_lit_expr)?;
if let Some(hi) = hi {
Ok(Pat::Range(PatRange {
attrs: Vec::new(),
qself,
path,
})),
limits: input.parse()?,
hi: input.call(pat_lit_expr)?,
})
lo: Box::new(Expr::Path(ExprPath {
attrs: Vec::new(),
qself,
path,
})),
limits,
hi,
}))
} else {
Ok(Pat::Verbatim(verbatim::between(begin, input)))
}
}

fn pat_range_half_open(input: ParseStream, begin: ParseBuffer) -> Result<Pat> {
let limits: RangeLimits = input.parse()?;
let hi = input.call(pat_lit_expr)?;
if hi.is_some() {
Ok(Pat::Verbatim(verbatim::between(begin, input)))
} else {
match limits {
RangeLimits::HalfOpen(dot2_token) => Ok(Pat::Rest(PatRest {
attrs: Vec::new(),
dot2_token,
})),
RangeLimits::Closed(_) => Err(input.error("expected range upper bound")),
}
}
}

fn pat_tuple(input: ParseStream) -> Result<PatTuple> {
Expand Down Expand Up @@ -669,14 +698,21 @@ mod parsing {
}

fn pat_lit_or_range(input: ParseStream) -> Result<Pat> {
let lo = input.call(pat_lit_expr)?;
let begin = input.fork();
let lo = input.call(pat_lit_expr)?.unwrap();
if input.peek(Token![..]) {
Ok(Pat::Range(PatRange {
attrs: Vec::new(),
lo,
limits: input.parse()?,
hi: input.call(pat_lit_expr)?,
}))
let limits: RangeLimits = input.parse()?;
let hi = input.call(pat_lit_expr)?;
if let Some(hi) = hi {
Ok(Pat::Range(PatRange {
attrs: Vec::new(),
lo,
limits,
hi,
}))
} else {
Ok(Pat::Verbatim(verbatim::between(begin, input)))
}
} else {
Ok(Pat::Lit(PatLit {
attrs: Vec::new(),
Expand All @@ -685,7 +721,17 @@ mod parsing {
}
}

fn pat_lit_expr(input: ParseStream) -> Result<Box<Expr>> {
fn pat_lit_expr(input: ParseStream) -> Result<Option<Box<Expr>>> {
if input.is_empty()
|| input.peek(Token![|])
|| input.peek(Token![=>])
|| input.peek(Token![:]) && !input.peek(Token![::])
|| input.peek(Token![,])
|| input.peek(Token![;])
{
return Ok(None);
}

let neg: Option<Token![-]> = input.parse()?;

let lookahead = input.lookahead1();
Expand All @@ -705,15 +751,15 @@ mod parsing {
return Err(lookahead.error());
};

Ok(Box::new(if let Some(neg) = neg {
Ok(Some(Box::new(if let Some(neg) = neg {
Expr::Unary(ExprUnary {
attrs: Vec::new(),
op: UnOp::Neg(neg),
expr: Box::new(expr),
})
} else {
expr
}))
})))
}

fn pat_slice(input: ParseStream) -> Result<PatSlice> {
Expand All @@ -737,13 +783,6 @@ mod parsing {
elems,
})
}

fn pat_rest(input: ParseStream) -> Result<PatRest> {
Ok(PatRest {
attrs: Vec::new(),
dot2_token: input.parse()?,
})
}
}

#[cfg(feature = "printing")]
Expand Down
3 changes: 0 additions & 3 deletions tests/repo/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -54,9 +54,6 @@ pub fn base_dir_filter(entry: &DirEntry) -> bool {
// TODO: visibility on enum variants
"tests/rust/src/test/pretty/enum-variant-vis.rs" |
"tests/rust/src/test/ui/parser/issue-65041-empty-vis-matcher-in-enum.rs" |
// TODO: half open range patterns
"tests/rust/src/test/ui/half-open-range-patterns/half-open-range-pats-syntactic-pass.rs" |
"tests/rust/src/test/ui/half-open-range-patterns/pat-tuple-4.rs" |
// TODO: inherent associated const
"tests/rust/src/test/ui/parser/impl-item-const-pass.rs" |
// TODO: inherent associated type
Expand Down