Add migration lint for reserved prefixes.

This commit is contained in:
Mara Bos 2021-06-14 12:56:49 +00:00 committed by lrh2000
parent 40fb2e9705
commit d837c00d10
4 changed files with 63 additions and 7 deletions

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@ -723,6 +723,15 @@ pub trait LintContext: Sized {
BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
}
BuiltinLintDiagnostics::ReservedPrefix(span) => {
db.span_label(span, "unknown prefix");
db.span_suggestion_verbose(
span.shrink_to_hi(),
"insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
" ".into(),
Applicability::MachineApplicable,
);
}
}
// Rewrap `db`, and pass control to the user.
decorate(LintDiagnosticBuilder::new(db));

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@ -2973,6 +2973,7 @@ declare_lint_pass! {
OR_PATTERNS_BACK_COMPAT,
LARGE_ASSIGNMENTS,
FUTURE_PRELUDE_COLLISION,
RESERVED_PREFIX,
]
}
@ -3263,3 +3264,39 @@ declare_lint! {
reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
};
}
declare_lint! {
/// The `reserved_prefix` lint detects identifiers that will be parsed as a
/// prefix instead in Rust 2021.
///
/// ### Example
///
/// ```rust,compile_fail
/// #![deny(reserved_prefix)]
///
/// macro_rules! m {
/// (z $x:expr) => ();
/// }
///
/// m!(z"hey");
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// In Rust 2015 and 2018, `z"hey"` is two tokens: the identifier `z`
/// followed by the string literal `"hey"`. In Rust 2021, the `z` is
/// considered a prefix for `"hey"`.
///
/// This lint suggests to add whitespace between the `z` and `"hey"` tokens
/// to keep them separated in Rust 2021.
pub RESERVED_PREFIX,
Allow,
"identifiers that will be parsed as a prefix in Rust 2021",
@future_incompatible = FutureIncompatibleInfo {
reference: "issue #84978 <https://github.com/rust-lang/rust/issues/84978>",
edition: Some(Edition::Edition2021),
};
crate_level_only
}

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@ -300,6 +300,7 @@ pub enum BuiltinLintDiagnostics {
ExternDepSpec(String, ExternDepSpec),
ProcMacroBackCompat(String),
OrPatternsBackCompat(Span, String),
ReservedPrefix(Span),
}
/// Lints that are buffered up early on in the `Session` before the

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@ -1,9 +1,11 @@
use rustc_ast::ast::AttrStyle;
use rustc_ast::ast::{self, AttrStyle};
use rustc_ast::token::{self, CommentKind, Token, TokenKind};
use rustc_ast::tokenstream::{Spacing, TokenStream};
use rustc_errors::{error_code, Applicability, DiagnosticBuilder, FatalError, PResult};
use rustc_lexer::unescape::{self, Mode};
use rustc_lexer::{Base, DocStyle, RawStrError};
use rustc_session::lint::builtin::RESERVED_PREFIX;
use rustc_session::lint::BuiltinLintDiagnostics;
use rustc_session::parse::ParseSess;
use rustc_span::edition::Edition;
use rustc_span::symbol::{sym, Symbol};
@ -498,17 +500,24 @@ impl<'a> StringReader<'a> {
FatalError.raise()
}
// See RFC 3101.
fn report_reserved_prefix(&self, start: BytePos) {
// See RFC 3101.
let prefix_span = self.mk_sp(start, self.pos);
let msg = format!("prefix `{}` is unknown", self.str_from_to(start, self.pos));
if self.sess.edition < Edition::Edition2021 {
self.sess.buffer_lint_with_diagnostic(
&RESERVED_PREFIX,
prefix_span,
ast::CRATE_NODE_ID,
&msg,
BuiltinLintDiagnostics::ReservedPrefix(prefix_span),
);
return;
}
let mut err = self.sess.span_diagnostic.struct_span_err(
self.mk_sp(start, self.pos),
&format!("prefix `{}` is unknown", self.str_from_to(start, self.pos)),
);
err.span_label(self.mk_sp(start, self.pos), "unknown prefix");
let mut err = self.sess.span_diagnostic.struct_span_err(prefix_span, &msg);
err.span_label(prefix_span, "unknown prefix");
err.span_suggestion_verbose(
self.mk_sp(self.pos, self.pos),
"consider inserting whitespace here",