diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 7ab0d3f35ea..5770c038e9e 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -10,13 +10,13 @@ use crate::errors::{
ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
- HelpIdentifierStartsWithNumber, InInTypo, IncorrectAwait, IncorrectSemicolon,
- IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType, QuestionMarkInTypeSugg,
- SelfParamNotFirst, StructLiteralBodyWithoutPath, StructLiteralBodyWithoutPathSugg,
- StructLiteralNeedingParens, StructLiteralNeedingParensSugg, SuggAddMissingLetStmt,
- SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator, UnexpectedConstInGenericParam,
- UnexpectedConstParamDeclaration, UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets,
- UseEqInstead, WrapType,
+ HelpIdentifierStartsWithNumber, HelpUseLatestEdition, InInTypo, IncorrectAwait,
+ IncorrectSemicolon, IncorrectUseOfAwait, PatternMethodParamWithoutBody, QuestionMarkInType,
+ QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
+ StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens, StructLiteralNeedingParensSugg,
+ SuggAddMissingLetStmt, SuggEscapeIdentifier, SuggRemoveComma, TernaryOperator,
+ UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
+ UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead, WrapType,
};
use crate::fluent_generated as fluent;
use crate::parser;
@@ -640,6 +640,28 @@ impl<'a> Parser<'a> {
}
}
+ // Try to detect an intended c-string literal while using a pre-2021 edition. The heuristic
+ // here is to identify a cooked, uninterpolated `c` id immediately followed by a string, or
+ // a cooked, uninterpolated `cr` id immediately followed by a string or a `#`, in an edition
+ // where c-string literals are not allowed. There is the very slight possibility of a false
+ // positive for a `cr#` that wasn't intended to start a c-string literal, but identifying
+ // that in the parser requires unbounded lookahead, so we only add a hint to the existing
+ // error rather than replacing it entirely.
+ if ((self.prev_token.kind == TokenKind::Ident(sym::c, false)
+ && matches!(&self.token.kind, TokenKind::Literal(token::Lit { kind: token::Str, .. })))
+ || (self.prev_token.kind == TokenKind::Ident(sym::cr, false)
+ && matches!(
+ &self.token.kind,
+ TokenKind::Literal(token::Lit { kind: token::Str, .. }) | token::Pound
+ )))
+ && self.prev_token.span.hi() == self.token.span.lo()
+ && !self.token.span.at_least_rust_2021()
+ {
+ err.note("you may be trying to write a c-string literal");
+ err.note("c-string literals require Rust 2021 or later");
+ HelpUseLatestEdition::new().add_to_diagnostic(&mut err);
+ }
+
// `pub` may be used for an item or `pub(crate)`
if self.prev_token.is_ident_named(sym::public)
&& (self.token.can_begin_item()
diff --git a/tests/ui/editions/edition-cstr-2015-2018.rs b/tests/ui/editions/edition-cstr-2015-2018.rs
new file mode 100644
index 00000000000..4c35c48646a
--- /dev/null
+++ b/tests/ui/editions/edition-cstr-2015-2018.rs
@@ -0,0 +1,62 @@
+macro_rules! construct { ($x:ident) => { $x"str" } }
+ //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ //~| NOTE expected one of 8 possible tokens
+
+macro_rules! contain { () => { c"str" } }
+ //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ //~| NOTE expected one of 8 possible tokens
+ //~| NOTE you may be trying to write a c-string literal
+ //~| NOTE c-string literals require Rust 2021 or later
+ //~| HELP pass `--edition 2021` to `rustc`
+ //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+
+fn check_macro_construct() {
+ construct!(c); //~ NOTE in this expansion of construct!
+}
+
+fn check_macro_contain() {
+ contain!();
+ //~^ NOTE in this expansion of contain!
+ //~| NOTE in this expansion of contain!
+ //~| NOTE in this expansion of contain!
+ //~| NOTE in this expansion of contain!
+ //~| NOTE in this expansion of contain!
+}
+
+fn check_basic() {
+ c"str";
+ //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ //~| NOTE expected one of 8 possible tokens
+ //~| NOTE you may be trying to write a c-string literal
+ //~| NOTE c-string literals require Rust 2021 or later
+ //~| HELP pass `--edition 2021` to `rustc`
+ //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}
+
+fn check_craw() {
+ cr"str";
+ //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ //~| NOTE expected one of 8 possible tokens
+ //~| NOTE you may be trying to write a c-string literal
+ //~| NOTE c-string literals require Rust 2021 or later
+ //~| HELP pass `--edition 2021` to `rustc`
+ //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}
+
+fn check_craw_hash() {
+ cr##"str"##;
+ //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `#`
+ //~| NOTE expected one of 8 possible tokens
+ //~| NOTE you may be trying to write a c-string literal
+ //~| NOTE c-string literals require Rust 2021 or later
+ //~| HELP pass `--edition 2021` to `rustc`
+ //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+}
+
+fn check_cstr_space() {
+ c "str";
+ //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ //~| NOTE expected one of 8 possible tokens
+}
+
+fn main() {}
diff --git a/tests/ui/editions/edition-cstr-2015-2018.stderr b/tests/ui/editions/edition-cstr-2015-2018.stderr
new file mode 100644
index 00000000000..b864df308ef
--- /dev/null
+++ b/tests/ui/editions/edition-cstr-2015-2018.stderr
@@ -0,0 +1,67 @@
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ --> $DIR/edition-cstr-2015-2018.rs:27:6
+ |
+LL | c"str";
+ | ^^^^^ expected one of 8 possible tokens
+ |
+ = note: you may be trying to write a c-string literal
+ = note: c-string literals require Rust 2021 or later
+ = help: pass `--edition 2021` to `rustc`
+ = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ --> $DIR/edition-cstr-2015-2018.rs:37:7
+ |
+LL | cr"str";
+ | ^^^^^ expected one of 8 possible tokens
+ |
+ = note: you may be trying to write a c-string literal
+ = note: c-string literals require Rust 2021 or later
+ = help: pass `--edition 2021` to `rustc`
+ = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `#`
+ --> $DIR/edition-cstr-2015-2018.rs:47:7
+ |
+LL | cr##"str"##;
+ | ^ expected one of 8 possible tokens
+ |
+ = note: you may be trying to write a c-string literal
+ = note: c-string literals require Rust 2021 or later
+ = help: pass `--edition 2021` to `rustc`
+ = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ --> $DIR/edition-cstr-2015-2018.rs:57:7
+ |
+LL | c "str";
+ | ^^^^^ expected one of 8 possible tokens
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ --> $DIR/edition-cstr-2015-2018.rs:1:44
+ |
+LL | macro_rules! construct { ($x:ident) => { $x"str" } }
+ | ^^^^^ expected one of 8 possible tokens
+...
+LL | construct!(c);
+ | ------------- in this macro invocation
+ |
+ = note: this error originates in the macro `construct` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+ --> $DIR/edition-cstr-2015-2018.rs:5:33
+ |
+LL | macro_rules! contain { () => { c"str" } }
+ | ^^^^^ expected one of 8 possible tokens
+...
+LL | contain!();
+ | ---------- in this macro invocation
+ |
+ = note: you may be trying to write a c-string literal
+ = note: c-string literals require Rust 2021 or later
+ = help: pass `--edition 2021` to `rustc`
+ = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+ = note: this error originates in the macro `contain` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 6 previous errors
+