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syntax: consolidate function parsing in item.rs #65362

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Oct 14, 2019
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syntax: consolidate function parsing in item.rs #65362

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285 changes: 4 additions & 281 deletions src/libsyntax/parse/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,20 +9,19 @@ mod path;
pub use path::PathStyle;
mod stmt;
mod generics;
use super::diagnostics::Error;

use crate::ast::{
self, DUMMY_NODE_ID, AttrStyle, Attribute, BindingMode, CrateSugar, Ident,
IsAsync, MacDelimiter, Mutability, Param, StrStyle, SelfKind, TyKind, Visibility,
VisibilityKind, Unsafety,
self, DUMMY_NODE_ID, AttrStyle, Attribute, CrateSugar, Ident,
IsAsync, MacDelimiter, Mutability, StrStyle, Visibility, VisibilityKind, Unsafety,
};
use crate::parse::{ParseSess, PResult, Directory, DirectoryOwnership, SeqSep, literal, token};
use crate::parse::diagnostics::{Error, dummy_arg};
use crate::parse::lexer::UnmatchedBrace;
use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
use crate::parse::token::{Token, TokenKind, DelimToken};
use crate::print::pprust;
use crate::ptr::P;
use crate::source_map::{self, respan};
use crate::source_map::respan;
use crate::symbol::{kw, sym, Symbol};
use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
use crate::ThinVec;
Expand Down Expand Up @@ -56,17 +55,6 @@ crate enum BlockMode {
Ignore,
}

/// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
struct ParamCfg {
/// Is `self` is allowed as the first parameter?
is_self_allowed: bool,
/// Is `...` allowed as the tail of the parameter list?
allow_c_variadic: bool,
/// `is_name_required` decides if, per-parameter,
/// the parameter must have a pattern or just a type.
is_name_required: fn(&token::Token) -> bool,
}

/// Like `maybe_whole_expr`, but for things other than expressions.
#[macro_export]
macro_rules! maybe_whole {
Expand Down Expand Up @@ -1105,271 +1093,6 @@ impl<'a> Parser<'a> {
res
}

/// Parses the parameter list of a function, including the `(` and `)` delimiters.
fn parse_fn_params(&mut self, mut cfg: ParamCfg) -> PResult<'a, Vec<Param>> {
let sp = self.token.span;
let is_trait_item = cfg.is_self_allowed;
let mut c_variadic = false;
// Parse the arguments, starting out with `self` being possibly allowed...
let (params, _) = self.parse_paren_comma_seq(|p| {
let param = p.parse_param_general(&cfg, is_trait_item);
// ...now that we've parsed the first argument, `self` is no longer allowed.
cfg.is_self_allowed = false;

match param {
Ok(param) => Ok(
if let TyKind::CVarArgs = param.ty.kind {
c_variadic = true;
if p.token != token::CloseDelim(token::Paren) {
p.span_err(
p.token.span,
"`...` must be the last argument of a C-variadic function",
);
// FIXME(eddyb) this should probably still push `CVarArgs`.
// Maybe AST validation/HIR lowering should emit the above error?
None
} else {
Some(param)
}
} else {
Some(param)
}
),
Err(mut e) => {
e.emit();
let lo = p.prev_span;
// Skip every token until next possible arg or end.
p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
// Create a placeholder argument for proper arg count (issue #34264).
let span = lo.to(p.prev_span);
Ok(Some(dummy_arg(Ident::new(kw::Invalid, span))))
}
}
})?;

let mut params: Vec<_> = params.into_iter().filter_map(|x| x).collect();

// Replace duplicated recovered params with `_` pattern to avoid unecessary errors.
self.deduplicate_recovered_params_names(&mut params);

if c_variadic && params.len() <= 1 {
self.span_err(
sp,
"C-variadic function must be declared with at least one named argument",
);
}

Ok(params)
}

/// Skips unexpected attributes and doc comments in this position and emits an appropriate
/// error.
/// This version of parse param doesn't necessarily require identifier names.
fn parse_param_general(&mut self, cfg: &ParamCfg, is_trait_item: bool) -> PResult<'a, Param> {
let lo = self.token.span;
let attrs = self.parse_outer_attributes()?;

// Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
if let Some(mut param) = self.parse_self_param()? {
param.attrs = attrs.into();
return if cfg.is_self_allowed {
Ok(param)
} else {
self.recover_bad_self_param(param, is_trait_item)
};
}

let is_name_required = match self.token.kind {
token::DotDotDot => false,
_ => (cfg.is_name_required)(&self.token),
};
let (pat, ty) = if is_name_required || self.is_named_param() {
debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);

let pat = self.parse_fn_param_pat()?;
if let Err(mut err) = self.expect(&token::Colon) {
return if let Some(ident) = self.parameter_without_type(
&mut err,
pat,
is_name_required,
cfg.is_self_allowed,
is_trait_item,
) {
err.emit();
Ok(dummy_arg(ident))
} else {
Err(err)
};
}

self.eat_incorrect_doc_comment_for_param_type();
(pat, self.parse_ty_common(true, true, cfg.allow_c_variadic)?)
} else {
debug!("parse_param_general ident_to_pat");
let parser_snapshot_before_ty = self.clone();
self.eat_incorrect_doc_comment_for_param_type();
let mut ty = self.parse_ty_common(true, true, cfg.allow_c_variadic);
if ty.is_ok() && self.token != token::Comma &&
self.token != token::CloseDelim(token::Paren) {
// This wasn't actually a type, but a pattern looking like a type,
// so we are going to rollback and re-parse for recovery.
ty = self.unexpected();
}
match ty {
Ok(ty) => {
let ident = Ident::new(kw::Invalid, self.prev_span);
let bm = BindingMode::ByValue(Mutability::Immutable);
let pat = self.mk_pat_ident(ty.span, bm, ident);
(pat, ty)
}
// If this is a C-variadic argument and we hit an error, return the error.
Err(err) if self.token == token::DotDotDot => return Err(err),
// Recover from attempting to parse the argument as a type without pattern.
Err(mut err) => {
err.cancel();
mem::replace(self, parser_snapshot_before_ty);
self.recover_arg_parse()?
}
}
};

let span = lo.to(self.token.span);

Ok(Param {
attrs: attrs.into(),
id: ast::DUMMY_NODE_ID,
is_placeholder: false,
pat,
span,
ty,
})
}

/// Returns the parsed optional self parameter and whether a self shortcut was used.
///
/// See `parse_self_param_with_attrs` to collect attributes.
fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
// Extract an identifier *after* having confirmed that the token is one.
let expect_self_ident = |this: &mut Self| {
match this.token.kind {
// Preserve hygienic context.
token::Ident(name, _) => {
let span = this.token.span;
this.bump();
Ident::new(name, span)
}
_ => unreachable!(),
}
};
// Is `self` `n` tokens ahead?
let is_isolated_self = |this: &Self, n| {
this.is_keyword_ahead(n, &[kw::SelfLower])
&& this.look_ahead(n + 1, |t| t != &token::ModSep)
};
// Is `mut self` `n` tokens ahead?
let is_isolated_mut_self = |this: &Self, n| {
this.is_keyword_ahead(n, &[kw::Mut])
&& is_isolated_self(this, n + 1)
};
// Parse `self` or `self: TYPE`. We already know the current token is `self`.
let parse_self_possibly_typed = |this: &mut Self, m| {
let eself_ident = expect_self_ident(this);
let eself_hi = this.prev_span;
let eself = if this.eat(&token::Colon) {
SelfKind::Explicit(this.parse_ty()?, m)
} else {
SelfKind::Value(m)
};
Ok((eself, eself_ident, eself_hi))
};
// Recover for the grammar `*self`, `*const self`, and `*mut self`.
let recover_self_ptr = |this: &mut Self| {
let msg = "cannot pass `self` by raw pointer";
let span = this.token.span;
this.struct_span_err(span, msg)
.span_label(span, msg)
.emit();

Ok((SelfKind::Value(Mutability::Immutable), expect_self_ident(this), this.prev_span))
};

// Parse optional `self` parameter of a method.
// Only a limited set of initial token sequences is considered `self` parameters; anything
// else is parsed as a normal function parameter list, so some lookahead is required.
let eself_lo = self.token.span;
let (eself, eself_ident, eself_hi) = match self.token.kind {
token::BinOp(token::And) => {
let eself = if is_isolated_self(self, 1) {
// `&self`
self.bump();
SelfKind::Region(None, Mutability::Immutable)
} else if is_isolated_mut_self(self, 1) {
// `&mut self`
self.bump();
self.bump();
SelfKind::Region(None, Mutability::Mutable)
} else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
// `&'lt self`
self.bump();
let lt = self.expect_lifetime();
SelfKind::Region(Some(lt), Mutability::Immutable)
} else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
// `&'lt mut self`
self.bump();
let lt = self.expect_lifetime();
self.bump();
SelfKind::Region(Some(lt), Mutability::Mutable)
} else {
// `&not_self`
return Ok(None);
};
(eself, expect_self_ident(self), self.prev_span)
}
// `*self`
token::BinOp(token::Star) if is_isolated_self(self, 1) => {
self.bump();
recover_self_ptr(self)?
}
// `*mut self` and `*const self`
token::BinOp(token::Star) if
self.look_ahead(1, |t| t.is_mutability())
&& is_isolated_self(self, 2) =>
{
self.bump();
self.bump();
recover_self_ptr(self)?
}
// `self` and `self: TYPE`
token::Ident(..) if is_isolated_self(self, 0) => {
parse_self_possibly_typed(self, Mutability::Immutable)?
}
// `mut self` and `mut self: TYPE`
token::Ident(..) if is_isolated_mut_self(self, 0) => {
self.bump();
parse_self_possibly_typed(self, Mutability::Mutable)?
}
_ => return Ok(None),
};

let eself = source_map::respan(eself_lo.to(eself_hi), eself);
Ok(Some(Param::from_self(ThinVec::default(), eself, eself_ident)))
}

fn is_named_param(&self) -> bool {
let offset = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
_ => 0,
}
token::BinOp(token::And) | token::AndAnd => 1,
_ if self.token.is_keyword(kw::Mut) => 1,
_ => 0,
};

self.look_ahead(offset, |t| t.is_ident()) &&
self.look_ahead(offset + 1, |t| t == &token::Colon)
}

fn is_crate_vis(&self) -> bool {
self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
}
Expand Down
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