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Replace pointer address checks in the parser #103700

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Replace pointer address checks in the parser #103700

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26 changes: 14 additions & 12 deletions compiler/rustc_parse/src/parser/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -829,12 +829,7 @@ impl<'a> Parser<'a> {
("cast", None)
};

// Save the memory location of expr before parsing any following postfix operators.
// This will be compared with the memory location of the output expression.
// If they different we can assume we parsed another expression because the existing expression is not reallocated.
let addr_before = &*cast_expr as *const _ as usize;
let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
let changed = addr_before != &*with_postfix as *const _ as usize;
let (with_postfix, changed) = self.parse_dot_or_call_expr_with_(cast_expr, span)?;

// Check if an illegal postfix operator has been added after the cast.
// If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
Expand Down Expand Up @@ -959,9 +954,9 @@ impl<'a> Parser<'a> {
// structure
let res = self.parse_dot_or_call_expr_with_(e0, lo);
if attrs.is_empty() {
res
res.map(|(expr, _)| expr)
} else {
res.map(|expr| {
res.map(|(expr, _)| {
expr.map(|mut expr| {
attrs.extend(expr.attrs);
expr.attrs = attrs;
Expand All @@ -971,7 +966,12 @@ impl<'a> Parser<'a> {
}
}

fn parse_dot_or_call_expr_with_(&mut self, mut e: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
fn parse_dot_or_call_expr_with_(
&mut self,
mut e: P<Expr>,
lo: Span,
) -> PResult<'a, (P<Expr>, bool)> {
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maybe a (doc) comment describing what this bool means would be nice,,

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galaxy brain: enum ParseDotOrCall { Changed(P<Expr>), Unchanged(P<Expr>) } 😅

but a bool is fine.

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enum ParseDotOrCall {
  Changed(P<Expr>),
  Unchanged(P<Expr>),
  CheckTheAddressJustToBeSure(P<Expr>),
}

let mut changed_expr = false;
loop {
let has_question = if self.prev_token.kind == TokenKind::Ident(kw::Return, false) {
// we are using noexpect here because we don't expect a `?` directly after a `return`
Expand All @@ -982,6 +982,7 @@ impl<'a> Parser<'a> {
};
if has_question {
// `expr?`
changed_expr = true;
e = self.mk_expr(lo.to(self.prev_token.span), ExprKind::Try(e));
continue;
}
Expand All @@ -998,13 +999,14 @@ impl<'a> Parser<'a> {
continue;
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You forgot a changed_expr on the previous line.

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@compiler-errors compiler-errors Oct 28, 2022 •
edited
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Add the corresponding UI test please:

fn main() {
    (1,) as (i32,) .0
    //~^ ERROR cast cannot be followed by a field access
}

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Actually, I feel like changed is redundant with the check on line 836:

if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {

Why did we need changed in the first place??

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Status update, as far as I can tell: we don't

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i like this

}
if self.expr_is_complete(&e) {
return Ok(e);
return Ok((e, changed_expr));
}
e = match self.token.kind {
token::OpenDelim(Delimiter::Parenthesis) => self.parse_fn_call_expr(lo, e),
token::OpenDelim(Delimiter::Bracket) => self.parse_index_expr(lo, e)?,
_ => return Ok(e),
}
_ => return Ok((e, changed_expr)),
};
changed_expr = true;
}
}

Expand Down