bjoernager/rust
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[rustc_parse] Forbid lets in certain places

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This commit is contained in:
Caio 2022-06-25 08:08:38 -03:00
parent e02d645110
commit 747586732b
13 changed files with 468 additions and 196 deletions
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30
compiler/rustc_parse/src/parser/expr.rs
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@ -7,6 +7,7 @@ use super::{
};
use crate::maybe_recover_from_interpolated_ty_qpath;
use core::mem;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, Token, TokenKind};
use rustc_ast::tokenstream::Spacing;
@ -26,7 +27,6 @@ use rustc_session::lint::BuiltinLintDiagnostics;
use rustc_span::source_map::{self, Span, Spanned};
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, Pos};
use std::mem;
/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
/// dropped into the token stream, which happens while parsing the result of
@ -2343,7 +2343,9 @@ impl<'a> Parser<'a> {
/// Parses the condition of a `if` or `while` expression.
fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let cond = self.with_let_management(true, |local_self| {
local_self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)
})?;
if let ExprKind::Let(..) = cond.kind {
// Remove the last feature gating of a `let` expression since it's stable.
@ -2356,6 +2358,13 @@ impl<'a> Parser<'a> {
/// Parses a `let $pat = $expr` pseudo-expression.
/// The `let` token has already been eaten.
fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
if !self.let_expr_allowed {
self.struct_span_err(
self.prev_token.span,
"expected expression, found `let` statement",
)
.emit();
}
let lo = self.prev_token.span;
let pat = self.parse_pat_allow_top_alt(
None,
@ -2672,6 +2681,8 @@ impl<'a> Parser<'a> {
}
pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
// Used to check the `let_chains` and `if_let_guard` features mostly by scaning
// `&&` tokens.
fn check_let_expr(expr: &Expr) -> (bool, bool) {
match expr.kind {
ExprKind::Binary(_, ref lhs, ref rhs) => {
@ -2694,7 +2705,7 @@ impl<'a> Parser<'a> {
)?;
let guard = if this.eat_keyword(kw::If) {
let if_span = this.prev_token.span;
let cond = this.parse_expr()?;
let cond = this.with_let_management(true, |local_this| local_this.parse_expr())?;
let (has_let_expr, does_not_have_bin_op) = check_let_expr(&cond);
if has_let_expr {
if does_not_have_bin_op {
@ -3256,4 +3267,17 @@ impl<'a> Parser<'a> {
Ok((res, trailing))
})
}
// Calls `f` with the internal `let_expr_allowed` set to `let_expr_allowed` and then
// sets the internal `let_expr_allowed` back to its original value.
fn with_let_management<T>(
&mut self,
let_expr_allowed: bool,
f: impl FnOnce(&mut Self) -> T,
) -> T {
let last_let_expr_allowed = mem::replace(&mut self.let_expr_allowed, let_expr_allowed);
let rslt = f(self);
self.let_expr_allowed = last_let_expr_allowed;
rslt
}
}