Add check for possible CStr literals in pre-2021

Author: chfogelman

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 +640,17 @@ impl<'a> Parser<'a> {
             }
         }
 
+        // extra info for `c"str"` before 2021 edition or `c "str"` in all editions
+        if self.prev_token.is_ident_named(Symbol::intern("c"))
+            && let TokenKind::Literal(token::Lit { kind: token::Str | token::StrRaw(..), .. }) =
+                &self.token.kind
+        {
+            err.note("you may be trying to declare a CStr literal");
+            err.note("`CStr` literals require edition 2021");
+            HelpUseLatestEdition::new().add_to_diagnostic(&mut err);
+            err.note("`c` modifier in CStr literal cannot be followed by whitespace");
+        }
+
         // `pub` may be used for an item or `pub(crate)`
         if self.prev_token.is_ident_named(sym::public)
             && (self.token.can_begin_item()

tests/ui/editions/edition-cstr-2015-2018.rs

@@ -0,0 +1,10 @@
+fn main() {
+    c"str";
+    //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+    //~| NOTE expected one of 8 possible tokens
+    //~| NOTE you may be trying to declare a CStr literal
+    //~| NOTE `CStr` literals require edition 2021
+    //~| HELP pass `--edition 2021` to `rustc`
+    //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+    //~| NOTE `c` modifier in CStr literal cannot be followed by whitespace
+}

tests/ui/editions/edition-cstr-2015-2018.stderr

@@ -0,0 +1,14 @@
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+  --> $DIR/edition-cstr-2015-2018.rs:2:6
+   |
+LL |     c"str";
+   |      ^^^^^ expected one of 8 possible tokens
+   |
+   = note: you may be trying to declare a CStr literal
+   = note: `CStr` literals require edition 2021
+   = help: pass `--edition 2021` to `rustc`
+   = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+   = note: `c` modifier in CStr literal cannot be followed by whitespace
+
+error: aborting due to 1 previous error
+

tests/ui/editions/edition-cstr-2021.rs

@@ -0,0 +1,13 @@
+// edition:2021
+
+fn main() {
+    c"str";   // This should pass
+    c "str";  // This should fail
+    //~^ ERROR expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+    //~| NOTE expected one of 8 possible tokens
+    //~| NOTE you may be trying to declare a CStr literal
+    //~| NOTE `CStr` literals require edition 2021
+    //~| HELP pass `--edition 2021` to `rustc`
+    //~| NOTE for more on editions, read https://doc.rust-lang.org/edition-guide
+    //~| NOTE `c` modifier in CStr literal cannot be followed by whitespace
+}

tests/ui/editions/edition-cstr-2021.stderr

@@ -0,0 +1,14 @@
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `"str"`
+  --> $DIR/edition-cstr-2021.rs:5:7
+   |
+LL |     c "str";  // This should fail
+   |       ^^^^^ expected one of 8 possible tokens
+   |
+   = note: you may be trying to declare a CStr literal
+   = note: `CStr` literals require edition 2021
+   = help: pass `--edition 2021` to `rustc`
+   = note: for more on editions, read https://doc.rust-lang.org/edition-guide
+   = note: `c` modifier in CStr literal cannot be followed by whitespace
+
+error: aborting due to 1 previous error
+