[macro_metavar_expr_concat] Add support for literals

Author: c410-f3r

compiler/rustc_expand/src/mbe/metavar_expr.rs

@@ -119,6 +119,8 @@ impl MetaVarExpr {
     }
 }
 
+/// Indicates what is placed in a `concat` parameter. For example, literals
+/// (`${concat("foo", "bar")}`) or adhoc identifiers (`${concat(foo, bar)}`).
 #[derive(Debug, Decodable, Encodable, PartialEq)]
 pub(crate) enum MetaVarExprConcatElem {
     /// Identifier WITHOUT a preceding dollar sign, which means that this identifier should be

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -6,9 +6,10 @@ use crate::mbe::macro_parser::{NamedMatch, NamedMatch::*};
 use crate::mbe::metavar_expr::{MetaVarExprConcatElem, RAW_IDENT_ERR};
 use crate::mbe::{self, KleeneOp, MetaVarExpr};
 use rustc_ast::mut_visit::{self, MutVisitor};
-use rustc_ast::token::IdentIsRaw;
-use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::token::{self, Delimiter, Nonterminal, Token, TokenKind};
+use rustc_ast::token::{IdentIsRaw, Lit, LitKind};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
+use rustc_ast::ExprKind;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{pluralize, Diag, DiagCtxtHandle, PResult};
 use rustc_parse::lexer::nfc_normalize;
@@ -750,7 +751,7 @@ fn transcribe_metavar_expr<'a>(
     Ok(())
 }
 
-/// Extracts an identifier that can be originated from a `$var:ident` variable or from a token tree.
+/// Extracts an metavariable value that can be an identifier, a token tree or a literal.
 fn extract_ident<'a>(
     dcx: DiagCtxtHandle<'a>,
     ident: Ident,
@@ -763,19 +764,29 @@ fn extract_ident<'a>(
             }
             return Ok(nt_ident.to_string());
         }
-        if let ParseNtResult::Tt(TokenTree::Token(
-            Token { kind: TokenKind::Ident(token_ident, is_raw), .. },
-            _,
-        )) = pnr
-        {
-            if let IdentIsRaw::Yes = is_raw {
-                return Err(dcx.struct_span_err(ident.span, RAW_IDENT_ERR));
+
+        if let ParseNtResult::Tt(TokenTree::Token(Token { kind, .. }, _)) = pnr {
+            if let TokenKind::Ident(symbol, is_raw) = kind {
+                if let IdentIsRaw::Yes = is_raw {
+                    return Err(dcx.struct_span_err(ident.span, RAW_IDENT_ERR));
+                }
+                return Ok(symbol.to_string());
             }
-            return Ok(token_ident.to_string());
+
+            if let TokenKind::Literal(Lit { kind: LitKind::Str, symbol, suffix: None }) = kind {
+                return Ok(symbol.to_string());
+            }
+        }
+
+        if let ParseNtResult::Nt(nt) = pnr
+            && let Nonterminal::NtLiteral(expr) = &**nt
+            && let ExprKind::Lit(Lit { kind: LitKind::Str, symbol, suffix: None }) = &expr.kind
+        {
+            return Ok(symbol.to_string());
         }
     }
     Err(dcx.struct_span_err(
         ident.span,
-        "`${concat(..)}` currently only accepts identifiers or meta-variables as parameters",
+        "`${concat(..)}` currently only accepts identifiers, token trees or literals",
     ))
 }

tests/ui/macros/macro-metavar-expr-concat/syntax-errors.rs

@@ -98,6 +98,16 @@ macro_rules! unsupported_literals {
     }};
 }
 
+macro_rules! bad_literal_parameter {
+    ($literal:literal) => {
+        const ${concat(_foo, $literal)}: () = ();
+        //~^ ERROR `${concat(..)}` is not generating a valid identifier
+        //~| ERROR `${concat(..)}` is not generating a valid identifier
+        //~| ERROR `${concat(..)}` is not generating a valid identifier
+        //~| ERROR `${concat(..)}` is not generating a valid identifier
+    }
+}
+
 fn main() {
     wrong_concat_declarations!(1);
 
@@ -113,4 +123,9 @@ fn main() {
     unsupported_literals!(_abc);
 
     empty!();
+
+    bad_literal_parameter!("\u{00BD}");
+    bad_literal_parameter!("\x41");
+    bad_literal_parameter!("🤷");
+    bad_literal_parameter!("d[-_-]b");
 }

tests/ui/macros/macro-metavar-expr-concat/syntax-errors.stderr

@@ -64,7 +64,7 @@ error: expected identifier or string literal
 LL |         let ${concat($ident, 1)}: () = ();
    |                              ^
 
-error: `${concat(..)}` currently only accepts identifiers or meta-variables as parameters
+error: `${concat(..)}` currently only accepts identifiers, token trees or literals
   --> $DIR/syntax-errors.rs:22:19
    |
 LL |         ${concat($ex, aaaa)}
@@ -131,5 +131,49 @@ LL |     empty!();
    |
    = note: this error originates in the macro `empty` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 18 previous errors
+error: `${concat(..)}` is not generating a valid identifier
+  --> $DIR/syntax-errors.rs:103:16
+   |
+LL |         const ${concat(_foo, $literal)}: () = ();
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |     bad_literal_parameter!("\u{00BD}");
+   |     ---------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `bad_literal_parameter` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `${concat(..)}` is not generating a valid identifier
+  --> $DIR/syntax-errors.rs:103:16
+   |
+LL |         const ${concat(_foo, $literal)}: () = ();
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |     bad_literal_parameter!("\x41");
+   |     ------------------------------ in this macro invocation
+   |
+   = note: this error originates in the macro `bad_literal_parameter` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `${concat(..)}` is not generating a valid identifier
+  --> $DIR/syntax-errors.rs:103:16
+   |
+LL |         const ${concat(_foo, $literal)}: () = ();
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |     bad_literal_parameter!("🤷");
+   |     ---------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `bad_literal_parameter` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `${concat(..)}` is not generating a valid identifier
+  --> $DIR/syntax-errors.rs:103:16
+   |
+LL |         const ${concat(_foo, $literal)}: () = ();
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |     bad_literal_parameter!("d[-_-]b");
+   |     --------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `bad_literal_parameter` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 22 previous errors
 

tests/ui/macros/macro-metavar-expr-concat/unicode-expansion.rs

@@ -3,12 +3,17 @@
 #![feature(macro_metavar_expr_concat)]
 
 macro_rules! turn_to_page {
-    ($ident:ident) => {
+    ($ident:ident, $literal:literal, $tt:tt) => {
         const ${concat("Ḧ", $ident)}: i32 = 394;
+        const ${concat("Ḧ", $literal)}: i32 = 394;
+        const ${concat("Ḧ", $tt)}: i32 = 394;
     };
 }
 
 fn main() {
-    turn_to_page!(P);
-    assert_eq!(ḦP, 394);
+    turn_to_page!(P1, "Ṕ2", Ṕ);
+    assert_eq!(ḦṔ, 394);
+    assert_eq!(ḦP1, 394);
+    assert_eq!(ḦṔ2, 394);
+
 }