Rollup merge of #143245 - tgross35:metavariable-expr-organization, r=petrochenkov

mbe: Add tests and restructure metavariable expressions

Add tests that show better diagnostics, and factor `concat` handling to a separate function. Each commit message has further details.

This performs the nonfunctional perparation for further changes such as https://github.com/rust-lang/rust/pull/142950 and https://github.com/rust-lang/rust/pull/142975 .

compiler/rustc_expand/messages.ftl

@@ -109,9 +109,6 @@ expand_malformed_feature_attribute =
 
 expand_meta_var_dif_seq_matchers = {$msg}
 
-expand_meta_var_expr_unrecognized_var =
-    variable `{$key}` is not recognized in meta-variable expression
-
 expand_missing_fragment_specifier = missing fragment specifier
     .note = fragment specifiers must be provided
     .suggestion_add_fragspec = try adding a specifier here
@@ -136,6 +133,9 @@ expand_module_multiple_candidates =
 expand_must_repeat_once =
     this must repeat at least once
 
+expand_mve_unrecognized_var =
+    variable `{$key}` is not recognized in meta-variable expression
+
 expand_non_inline_modules_in_proc_macro_input_are_unstable =
     non-inline modules in proc macro input are unstable
 

compiler/rustc_expand/src/errors.rs

@@ -27,14 +27,6 @@ pub(crate) struct CountRepetitionMisplaced {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(expand_meta_var_expr_unrecognized_var)]
-pub(crate) struct MetaVarExprUnrecognizedVar {
-    #[primary_span]
-    pub span: Span,
-    pub key: MacroRulesNormalizedIdent,
-}
-
 #[derive(Diagnostic)]
 #[diag(expand_var_still_repeating)]
 pub(crate) struct VarStillRepeating {
@@ -499,3 +491,16 @@ pub(crate) struct ProcMacroBackCompat {
     pub crate_name: String,
     pub fixed_version: String,
 }
+
+pub(crate) use metavar_exprs::*;
+mod metavar_exprs {
+    use super::*;
+
+    #[derive(Diagnostic)]
+    #[diag(expand_mve_unrecognized_var)]
+    pub(crate) struct MveUnrecognizedVar {
+        #[primary_span]
+        pub span: Span,
+        pub key: MacroRulesNormalizedIdent,
+    }
+}

compiler/rustc_expand/src/mbe/metavar_expr.rs

@@ -47,46 +47,7 @@ impl MetaVarExpr {
         check_trailing_token(&mut iter, psess)?;
         let mut iter = args.iter();
         let rslt = match ident.as_str() {
-            "concat" => {
-                let mut result = Vec::new();
-                loop {
-                    let is_var = try_eat_dollar(&mut iter);
-                    let token = parse_token(&mut iter, psess, outer_span)?;
-                    let element = if is_var {
-                        MetaVarExprConcatElem::Var(parse_ident_from_token(psess, token)?)
-                    } else if let TokenKind::Literal(Lit {
-                        kind: token::LitKind::Str,
-                        symbol,
-                        suffix: None,
-                    }) = token.kind
-                    {
-                        MetaVarExprConcatElem::Literal(symbol)
-                    } else {
-                        match parse_ident_from_token(psess, token) {
-                            Err(err) => {
-                                err.cancel();
-                                return Err(psess
-                                    .dcx()
-                                    .struct_span_err(token.span, UNSUPPORTED_CONCAT_ELEM_ERR));
-                            }
-                            Ok(elem) => MetaVarExprConcatElem::Ident(elem),
-                        }
-                    };
-                    result.push(element);
-                    if iter.peek().is_none() {
-                        break;
-                    }
-                    if !try_eat_comma(&mut iter) {
-                        return Err(psess.dcx().struct_span_err(outer_span, "expected comma"));
-                    }
-                }
-                if result.len() < 2 {
-                    return Err(psess
-                        .dcx()
-                        .struct_span_err(ident.span, "`concat` must have at least two elements"));
-                }
-                MetaVarExpr::Concat(result.into())
-            }
+            "concat" => parse_concat(&mut iter, psess, outer_span, ident.span)?,
             "count" => parse_count(&mut iter, psess, ident.span)?,
             "ignore" => {
                 eat_dollar(&mut iter, psess, ident.span)?;
@@ -126,20 +87,6 @@ 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
-    /// interpreted as a literal.
-    Ident(Ident),
-    /// For example, a number or a string.
-    Literal(Symbol),
-    /// Identifier WITH a preceding dollar sign, which means that this identifier should be
-    /// expanded and interpreted as a variable.
-    Var(Ident),
-}
-
 // Checks if there are any remaining tokens. For example, `${ignore(ident ... a b c ...)}`
 fn check_trailing_token<'psess>(
     iter: &mut TokenStreamIter<'_>,
@@ -156,6 +103,64 @@ fn check_trailing_token<'psess>(
     }
 }
 
+/// 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
+    /// interpreted as a literal.
+    Ident(Ident),
+    /// For example, a number or a string.
+    Literal(Symbol),
+    /// Identifier WITH a preceding dollar sign, which means that this identifier should be
+    /// expanded and interpreted as a variable.
+    Var(Ident),
+}
+
+/// Parse a meta-variable `concat` expression: `concat($metavar, ident, ...)`.
+fn parse_concat<'psess>(
+    iter: &mut TokenStreamIter<'_>,
+    psess: &'psess ParseSess,
+    outer_span: Span,
+    expr_ident_span: Span,
+) -> PResult<'psess, MetaVarExpr> {
+    let mut result = Vec::new();
+    loop {
+        let is_var = try_eat_dollar(iter);
+        let token = parse_token(iter, psess, outer_span)?;
+        let element = if is_var {
+            MetaVarExprConcatElem::Var(parse_ident_from_token(psess, token)?)
+        } else if let TokenKind::Literal(Lit { kind: token::LitKind::Str, symbol, suffix: None }) =
+            token.kind
+        {
+            MetaVarExprConcatElem::Literal(symbol)
+        } else {
+            match parse_ident_from_token(psess, token) {
+                Err(err) => {
+                    err.cancel();
+                    return Err(psess
+                        .dcx()
+                        .struct_span_err(token.span, UNSUPPORTED_CONCAT_ELEM_ERR));
+                }
+                Ok(elem) => MetaVarExprConcatElem::Ident(elem),
+            }
+        };
+        result.push(element);
+        if iter.peek().is_none() {
+            break;
+        }
+        if !try_eat_comma(iter) {
+            return Err(psess.dcx().struct_span_err(outer_span, "expected comma"));
+        }
+    }
+    if result.len() < 2 {
+        return Err(psess
+            .dcx()
+            .struct_span_err(expr_ident_span, "`concat` must have at least two elements"));
+    }
+    Ok(MetaVarExpr::Concat(result.into()))
+}
+
 /// Parse a meta-variable `count` expression: `count(ident[, depth])`
 fn parse_count<'psess>(
     iter: &mut TokenStreamIter<'_>,

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -17,7 +17,7 @@ use rustc_span::{
 use smallvec::{SmallVec, smallvec};
 
 use crate::errors::{
-    CountRepetitionMisplaced, MetaVarExprUnrecognizedVar, MetaVarsDifSeqMatchers, MustRepeatOnce,
+    CountRepetitionMisplaced, MetaVarsDifSeqMatchers, MustRepeatOnce, MveUnrecognizedVar,
     NoSyntaxVarsExprRepeat, VarStillRepeating,
 };
 use crate::mbe::macro_parser::NamedMatch;
@@ -879,7 +879,7 @@ where
 {
     let span = ident.span;
     let key = MacroRulesNormalizedIdent::new(ident);
-    interp.get(&key).ok_or_else(|| dcx.create_err(MetaVarExprUnrecognizedVar { span, key }))
+    interp.get(&key).ok_or_else(|| dcx.create_err(MveUnrecognizedVar { span, key }))
 }
 
 /// Used by meta-variable expressions when an user input is out of the actual declared bounds. For

src/tools/tidy/src/issues.txt

@@ -2846,7 +2846,6 @@ ui/macros/issue-98466.rs
 ui/macros/issue-99261.rs
 ui/macros/issue-99265.rs
 ui/macros/issue-99907.rs
-ui/macros/rfc-3086-metavar-expr/issue-111904.rs
 ui/malformed/issue-107423-unused-delim-only-one-no-pair.rs
 ui/malformed/issue-69341-malformed-derive-inert.rs
 ui/marker_trait_attr/issue-61651-type-mismatch.rs

tests/ui/macros/metavar-expressions/concat-hygiene.stderr

@@ -1,5 +1,5 @@
 error[E0425]: cannot find value `abcdef` in this scope
-  --> $DIR/hygiene.rs:5:10
+  --> $DIR/concat-hygiene.rs:5:10
    |
 LL |         ${concat($lhs, $rhs)}
    |          ^^^^^^^^^^^^^^^^^^^^ not found in this scope

tests/ui/macros/metavar-expressions/concat-raw-identifiers.stderr

@@ -1,47 +1,47 @@
 error: expected identifier or string literal
-  --> $DIR/raw-identifiers.rs:28:22
+  --> $DIR/concat-raw-identifiers.rs:28:22
    |
 LL |         let ${concat(r#abc, abc)}: () = ();
    |                      ^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/raw-identifiers.rs:32:27
+  --> $DIR/concat-raw-identifiers.rs:32:27
    |
 LL |         let ${concat(abc, r#abc)}: () = ();
    |                           ^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/raw-identifiers.rs:35:22
+  --> $DIR/concat-raw-identifiers.rs:35:22
    |
 LL |         let ${concat(r#abc, r#abc)}: () = ();
    |                      ^^^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:5:28
+  --> $DIR/concat-raw-identifiers.rs:5:28
    |
 LL |         let ${concat(abc, $rhs)}: () = ();
    |                            ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:12:23
+  --> $DIR/concat-raw-identifiers.rs:12:23
    |
 LL |         let ${concat($lhs, abc)}: () = ();
    |                       ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:19:23
+  --> $DIR/concat-raw-identifiers.rs:19:23
    |
 LL |         let ${concat($lhs, $rhs)}: () = ();
    |                       ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:19:29
+  --> $DIR/concat-raw-identifiers.rs:19:29
    |
 LL |         let ${concat($lhs, $rhs)}: () = ();
    |                             ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:19:23
+  --> $DIR/concat-raw-identifiers.rs:19:23
    |
 LL |         let ${concat($lhs, $rhs)}: () = ();
    |                       ^^^
@@ -49,31 +49,31 @@ LL |         let ${concat($lhs, $rhs)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:42:28
+  --> $DIR/concat-raw-identifiers.rs:42:28
    |
 LL |         let ${concat(abc, $rhs)}: () = ();
    |                            ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:49:23
+  --> $DIR/concat-raw-identifiers.rs:49:23
    |
 LL |         let ${concat($lhs, abc)}: () = ();
    |                       ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:56:23
+  --> $DIR/concat-raw-identifiers.rs:56:23
    |
 LL |         let ${concat($lhs, $rhs)}: () = ();
    |                       ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:56:29
+  --> $DIR/concat-raw-identifiers.rs:56:29
    |
 LL |         let ${concat($lhs, $rhs)}: () = ();
    |                             ^^^
 
 error: `${concat(..)}` currently does not support raw identifiers
-  --> $DIR/raw-identifiers.rs:56:23
+  --> $DIR/concat-raw-identifiers.rs:56:23
    |
 LL |         let ${concat($lhs, $rhs)}: () = ();
    |                       ^^^
@@ -81,7 +81,7 @@ LL |         let ${concat($lhs, $rhs)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: expected pattern, found `$`
-  --> $DIR/raw-identifiers.rs:28:13
+  --> $DIR/concat-raw-identifiers.rs:28:13
    |
 LL |         let ${concat(r#abc, abc)}: () = ();
    |             ^ expected pattern

tests/ui/macros/metavar-expressions/concat-repetitions.stderr

@@ -1,17 +1,17 @@
 error: invalid syntax
-  --> $DIR/repetitions.rs:14:20
+  --> $DIR/concat-repetitions.rs:14:20
    |
 LL |             const ${concat($a, Z)}: i32 = 3;
    |                    ^^^^^^^^^^^^^^^
 
 error: invalid syntax
-  --> $DIR/repetitions.rs:22:17
+  --> $DIR/concat-repetitions.rs:22:17
    |
 LL |         read::<${concat($t, $en)}>()
    |                 ^^^^^^^^^^^^^^^^^
 
 error: invalid syntax
-  --> $DIR/repetitions.rs:22:17
+  --> $DIR/concat-repetitions.rs:22:17
    |
 LL |         read::<${concat($t, $en)}>()
    |                 ^^^^^^^^^^^^^^^^^

tests/ui/macros/metavar-expressions/concat-trace-errors.rs

@@ -0,0 +1,33 @@
+// Our diagnostics should be able to point to a specific input that caused an invalid
+// identifier.
+
+#![feature(macro_metavar_expr_concat)]
+
+// See what we can do without expanding anything
+macro_rules! pre_expansion {
+    ($a:ident) => {
+        ${concat("hi", " bye ")};
+        ${concat("hi", "-", "bye")};
+        ${concat($a, "-")};
+    }
+}
+
+macro_rules! post_expansion {
+    ($a:literal) => {
+        const _: () = ${concat("hi", $a, "bye")};
+        //~^ ERROR is not generating a valid identifier
+    }
+}
+
+post_expansion!("!");
+
+macro_rules! post_expansion_many {
+    ($a:ident, $b:ident, $c:ident, $d:literal, $e:ident) => {
+        const _: () = ${concat($a, $b, $c, $d, $e)};
+        //~^ ERROR is not generating a valid identifier
+    }
+}
+
+post_expansion_many!(a, b, c, ".d", e);
+
+fn main() {}

tests/ui/macros/metavar-expressions/concat-trace-errors.stderr

@@ -0,0 +1,24 @@
+error: `${concat(..)}` is not generating a valid identifier
+  --> $DIR/concat-trace-errors.rs:17:24
+   |
+LL |         const _: () = ${concat("hi", $a, "bye")};
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | post_expansion!("!");
+   | -------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `post_expansion` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `${concat(..)}` is not generating a valid identifier
+  --> $DIR/concat-trace-errors.rs:26:24
+   |
+LL |         const _: () = ${concat($a, $b, $c, $d, $e)};
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | post_expansion_many!(a, b, c, ".d", e);
+   | -------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `post_expansion_many` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 2 previous errors
+

tests/ui/macros/metavar-expressions/concat-usage-errors.rs

@@ -1,6 +1,8 @@
+//@ edition: 2021
+
 #![feature(macro_metavar_expr_concat)]
 
-macro_rules! wrong_concat_declarations {
+macro_rules! syntax_errors {
     ($ex:expr) => {
         ${concat()}
         //~^ ERROR expected identifier
@@ -90,11 +92,31 @@ macro_rules! unsupported_literals {
         //~| ERROR expected pattern
         let ${concat(_a, 1)}: () = ();
         //~^ ERROR expected identifier or string literal
+        let ${concat(_a, 1.5)}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat(_a, c"hi")}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat(_a, b"hi")}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat(_a, b'b')}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat(_a, b'b')}: () = ();
+        //~^ ERROR expected identifier or string literal
 
         let ${concat($ident, 'b')}: () = ();
         //~^ ERROR expected identifier or string literal
         let ${concat($ident, 1)}: () = ();
         //~^ ERROR expected identifier or string literal
+        let ${concat($ident, 1.5)}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat($ident, c"hi")}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat($ident, b"hi")}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat($ident, b'b')}: () = ();
+        //~^ ERROR expected identifier or string literal
+        let ${concat($ident, b'b')}: () = ();
+        //~^ ERROR expected identifier or string literal
     }};
 }
 
@@ -132,7 +154,7 @@ macro_rules! bad_tt_literal {
 }
 
 fn main() {
-    wrong_concat_declarations!(1);
+    syntax_errors!(1);
 
     dollar_sign_without_referenced_ident!(VAR);
 

tests/ui/macros/metavar-expressions/concat-usage-errors.stderr

@@ -1,71 +1,131 @@
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:5:10
+  --> $DIR/concat-usage-errors.rs:7:10
    |
 LL |         ${concat()}
    |          ^^^^^^^^^^
 
 error: `concat` must have at least two elements
-  --> $DIR/syntax-errors.rs:8:11
+  --> $DIR/concat-usage-errors.rs:10:11
    |
 LL |         ${concat(aaaa)}
    |           ^^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:11:10
+  --> $DIR/concat-usage-errors.rs:13:10
    |
 LL |         ${concat(aaaa,)}
    |          ^^^^^^^^^^^^^^^
 
 error: expected comma
-  --> $DIR/syntax-errors.rs:16:10
+  --> $DIR/concat-usage-errors.rs:18:10
    |
 LL |         ${concat(aaaa aaaa)}
    |          ^^^^^^^^^^^^^^^^^^^
 
 error: `concat` must have at least two elements
-  --> $DIR/syntax-errors.rs:19:11
+  --> $DIR/concat-usage-errors.rs:21:11
    |
 LL |         ${concat($ex)}
    |           ^^^^^^
 
 error: expected comma
-  --> $DIR/syntax-errors.rs:25:10
+  --> $DIR/concat-usage-errors.rs:27:10
    |
 LL |         ${concat($ex, aaaa 123)}
    |          ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:28:10
+  --> $DIR/concat-usage-errors.rs:30:10
    |
 LL |         ${concat($ex, aaaa,)}
    |          ^^^^^^^^^^^^^^^^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:88:26
+  --> $DIR/concat-usage-errors.rs:90:26
    |
 LL |         let ${concat(_a, 'b')}: () = ();
    |                          ^^^
 
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:91:26
+  --> $DIR/concat-usage-errors.rs:93:26
    |
 LL |         let ${concat(_a, 1)}: () = ();
    |                          ^
 
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:94:30
+  --> $DIR/concat-usage-errors.rs:95:26
+   |
+LL |         let ${concat(_a, 1.5)}: () = ();
+   |                          ^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:97:26
+   |
+LL |         let ${concat(_a, c"hi")}: () = ();
+   |                          ^^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:99:26
+   |
+LL |         let ${concat(_a, b"hi")}: () = ();
+   |                          ^^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:101:26
+   |
+LL |         let ${concat(_a, b'b')}: () = ();
+   |                          ^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:103:26
+   |
+LL |         let ${concat(_a, b'b')}: () = ();
+   |                          ^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:106:30
    |
 LL |         let ${concat($ident, 'b')}: () = ();
    |                              ^^^
 
 error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:96:30
+  --> $DIR/concat-usage-errors.rs:108:30
    |
 LL |         let ${concat($ident, 1)}: () = ();
    |                              ^
 
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:110:30
+   |
+LL |         let ${concat($ident, 1.5)}: () = ();
+   |                              ^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:112:30
+   |
+LL |         let ${concat($ident, c"hi")}: () = ();
+   |                              ^^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:114:30
+   |
+LL |         let ${concat($ident, b"hi")}: () = ();
+   |                              ^^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:116:30
+   |
+LL |         let ${concat($ident, b'b')}: () = ();
+   |                              ^^^^
+
+error: expected identifier or string literal
+  --> $DIR/concat-usage-errors.rs:118:30
+   |
+LL |         let ${concat($ident, b'b')}: () = ();
+   |                              ^^^^
+
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:22:19
+  --> $DIR/concat-usage-errors.rs:24:19
    |
 LL |         ${concat($ex, aaaa)}
    |                   ^^
@@ -73,13 +133,13 @@ LL |         ${concat($ex, aaaa)}
    = note: currently only string literals are supported
 
 error: variable `foo` is not recognized in meta-variable expression
-  --> $DIR/syntax-errors.rs:35:30
+  --> $DIR/concat-usage-errors.rs:37:30
    |
 LL |         const ${concat(FOO, $foo)}: i32 = 2;
    |                              ^^^
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/syntax-errors.rs:42:14
+  --> $DIR/concat-usage-errors.rs:44:14
    |
 LL |         let ${concat("1", $ident)}: () = ();
    |              ^^^^^^^^^^^^^^^^^^^^^
@@ -90,7 +150,7 @@ LL |     starting_number!(_abc);
    = note: this error originates in the macro `starting_number` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/syntax-errors.rs:55:14
+  --> $DIR/concat-usage-errors.rs:57:14
    |
 LL |         let ${concat("\u{00BD}", $ident)}: () = ();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -101,7 +161,7 @@ LL |     starting_invalid_unicode!(_abc);
    = note: this error originates in the macro `starting_invalid_unicode` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/syntax-errors.rs:74:14
+  --> $DIR/concat-usage-errors.rs:76:14
    |
 LL |         let ${concat($ident, "\u{00BD}")}: () = ();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -112,7 +172,7 @@ LL |     ending_invalid_unicode!(_abc);
    = note: this error originates in the macro `ending_invalid_unicode` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: expected pattern, found `$`
-  --> $DIR/syntax-errors.rs:88:13
+  --> $DIR/concat-usage-errors.rs:90:13
    |
 LL |         let ${concat(_a, 'b')}: () = ();
    |             ^ expected pattern
@@ -123,7 +183,7 @@ LL |     unsupported_literals!(_abc);
    = note: this error originates in the macro `unsupported_literals` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/syntax-errors.rs:81:14
+  --> $DIR/concat-usage-errors.rs:83:14
    |
 LL |         let ${concat("", "")}: () = ();
    |              ^^^^^^^^^^^^^^^^
@@ -134,7 +194,7 @@ LL |     empty!();
    = note: this error originates in the macro `empty` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -145,7 +205,7 @@ LL |     bad_literal_string!("\u{00BD}");
    = note: this error originates in the macro `bad_literal_string` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -156,7 +216,7 @@ LL |     bad_literal_string!("\x41");
    = note: this error originates in the macro `bad_literal_string` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -167,7 +227,7 @@ LL |     bad_literal_string!("🤷");
    = note: this error originates in the macro `bad_literal_string` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -178,7 +238,7 @@ LL |     bad_literal_string!("d[-_-]b");
    = note: this error originates in the macro `bad_literal_string` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -189,7 +249,7 @@ LL |     bad_literal_string!("-1");
    = note: this error originates in the macro `bad_literal_string` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -200,7 +260,7 @@ LL |     bad_literal_string!("1.0");
    = note: this error originates in the macro `bad_literal_string` (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
+  --> $DIR/concat-usage-errors.rs:125:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -211,7 +271,7 @@ LL |     bad_literal_string!("'1'");
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:116:31
+  --> $DIR/concat-usage-errors.rs:138:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -219,7 +279,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: currently only string literals are supported
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:116:31
+  --> $DIR/concat-usage-errors.rs:138:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -228,7 +288,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:116:31
+  --> $DIR/concat-usage-errors.rs:138:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -237,7 +297,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:116:31
+  --> $DIR/concat-usage-errors.rs:138:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -246,7 +306,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:116:31
+  --> $DIR/concat-usage-errors.rs:138:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -255,7 +315,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:127:31
+  --> $DIR/concat-usage-errors.rs:149:31
    |
 LL |         const ${concat(_foo, $tt)}: () = ();
    |                               ^^
@@ -263,7 +323,7 @@ LL |         const ${concat(_foo, $tt)}: () = ();
    = note: currently only string literals are supported
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:127:31
+  --> $DIR/concat-usage-errors.rs:149:31
    |
 LL |         const ${concat(_foo, $tt)}: () = ();
    |                               ^^
@@ -272,7 +332,7 @@ LL |         const ${concat(_foo, $tt)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/syntax-errors.rs:127:31
+  --> $DIR/concat-usage-errors.rs:149:31
    |
 LL |         const ${concat(_foo, $tt)}: () = ();
    |                               ^^
@@ -280,5 +340,5 @@ LL |         const ${concat(_foo, $tt)}: () = ();
    = note: currently only string literals are supported
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 33 previous errors
+error: aborting due to 43 previous errors
 

tests/ui/macros/metavar-expressions/count-empty-index-arg.rs

@@ -1,3 +1,6 @@
+// Issue: https://github.com/rust-lang/rust/issues/111904
+// Ensure that a trailing `,` is not interpreted as a `0`.
+
 #![feature(macro_metavar_expr)]
 
 macro_rules! foo {
@@ -10,5 +13,4 @@ fn test() {
     foo!(a, a; b, b);
 }
 
-fn main() {
-}
+fn main() {}

tests/ui/macros/metavar-expressions/count-empty-index-arg.stderr

@@ -1,11 +1,11 @@
 error: `count` followed by a comma must have an associated index indicating its depth
-  --> $DIR/issue-111904.rs:4:37
+  --> $DIR/count-empty-index-arg.rs:7:37
    |
 LL |     ( $( $($t:ident),* );* ) => { ${count($t,)} }
    |                                     ^^^^^
 
 error: expected expression, found `$`
-  --> $DIR/issue-111904.rs:4:35
+  --> $DIR/count-empty-index-arg.rs:7:35
    |
 LL |     ( $( $($t:ident),* );* ) => { ${count($t,)} }
    |                                   ^ expected expression

tests/ui/macros/metavar-expressions/syntax-errors.rs

@@ -0,0 +1,117 @@
+// General syntax errors that apply to all matavariable expressions
+//
+// We don't invoke the macros here to ensure code gets rejected at the definition rather than
+// only when expanded.
+
+#![feature(macro_metavar_expr)]
+
+macro_rules! dollar_dollar_in_the_lhs {
+    ( $$ $a:ident ) => {
+        //~^ ERROR unexpected token: $
+    };
+}
+
+macro_rules! metavar_in_the_lhs {
+    ( ${ len() } ) => {
+        //~^ ERROR unexpected token: {
+        //~| ERROR expected one of: `*`, `+`, or `?`
+    };
+}
+
+macro_rules! metavar_token_without_ident {
+    ( $( $i:ident ),* ) => { ${ ignore() } };
+    //~^ ERROR meta-variable expressions must be referenced using a dollar sign
+}
+
+macro_rules! metavar_with_literal_suffix {
+    ( $( $i:ident ),* ) => { ${ index(1u32) } };
+    //~^ ERROR only unsuffixes integer literals are supported in meta-variable expressions
+}
+
+macro_rules! mve_without_parens {
+    ( $( $i:ident ),* ) => { ${ count } };
+    //~^ ERROR meta-variable expression parameter must be wrapped in parentheses
+}
+
+#[rustfmt::skip]
+macro_rules! empty_expression {
+    () => { ${} };
+    //~^ ERROR expected identifier or string literal
+}
+
+#[rustfmt::skip]
+macro_rules! open_brackets_with_lit {
+     () => { ${ "hi" } };
+     //~^ ERROR expected identifier
+ }
+
+macro_rules! mve_wrong_delim {
+    ( $( $i:ident ),* ) => { ${ count{i} } };
+    //~^ ERROR meta-variable expression parameter must be wrapped in parentheses
+}
+
+macro_rules! invalid_metavar {
+    () => { ${ignore($123)} }
+    //~^ ERROR expected identifier, found `123`
+}
+
+#[rustfmt::skip]
+macro_rules! open_brackets_with_group {
+    ( $( $i:ident ),* ) => { ${ {} } };
+    //~^ ERROR expected identifier
+}
+
+macro_rules! extra_garbage_after_metavar {
+    ( $( $i:ident ),* ) => {
+        ${count() a b c}
+        //~^ ERROR unexpected token: a
+        ${count($i a b c)}
+        //~^ ERROR unexpected token: a
+        ${count($i, 1 a b c)}
+        //~^ ERROR unexpected token: a
+        ${count($i) a b c}
+        //~^ ERROR unexpected token: a
+
+        ${ignore($i) a b c}
+        //~^ ERROR unexpected token: a
+        ${ignore($i a b c)}
+        //~^ ERROR unexpected token: a
+
+        ${index() a b c}
+        //~^ ERROR unexpected token: a
+        ${index(1 a b c)}
+        //~^ ERROR unexpected token: a
+
+        ${index() a b c}
+        //~^ ERROR unexpected token: a
+        ${index(1 a b c)}
+        //~^ ERROR unexpected token: a
+    };
+}
+
+const IDX: usize = 1;
+macro_rules! metavar_depth_is_not_literal {
+    ( $( $i:ident ),* ) => { ${ index(IDX) } };
+    //~^ ERROR meta-variable expression depth must be a literal
+}
+
+macro_rules! unknown_count_ident {
+    ( $( $i:ident )* ) => {
+        ${count(foo)}
+        //~^ ERROR meta-variable expressions must be referenced using a dollar sign
+    };
+}
+
+macro_rules! unknown_ignore_ident {
+    ( $( $i:ident )* ) => {
+        ${ignore(bar)}
+        //~^ ERROR meta-variable expressions must be referenced using a dollar sign
+    };
+}
+
+macro_rules! unknown_metavar {
+    ( $( $i:ident ),* ) => { ${ aaaaaaaaaaaaaa(i) } };
+    //~^ ERROR unrecognized meta-variable expression
+}
+
+fn main() {}

tests/ui/macros/metavar-expressions/syntax-errors.stderr

@@ -0,0 +1,224 @@
+error: unexpected token: $
+  --> $DIR/syntax-errors.rs:9:8
+   |
+LL |     ( $$ $a:ident ) => {
+   |        ^
+
+note: `$$` and meta-variable expressions are not allowed inside macro parameter definitions
+  --> $DIR/syntax-errors.rs:9:8
+   |
+LL |     ( $$ $a:ident ) => {
+   |        ^
+
+error: unexpected token: {
+  --> $DIR/syntax-errors.rs:15:8
+   |
+LL |     ( ${ len() } ) => {
+   |        ^^^^^^^^^
+
+note: `$$` and meta-variable expressions are not allowed inside macro parameter definitions
+  --> $DIR/syntax-errors.rs:15:8
+   |
+LL |     ( ${ len() } ) => {
+   |        ^^^^^^^^^
+
+error: expected one of: `*`, `+`, or `?`
+  --> $DIR/syntax-errors.rs:15:8
+   |
+LL |     ( ${ len() } ) => {
+   |        ^^^^^^^^^
+
+error: meta-variables within meta-variable expressions must be referenced using a dollar sign
+  --> $DIR/syntax-errors.rs:22:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ ignore() } };
+   |                                 ^^^^^^
+
+error: only unsuffixes integer literals are supported in meta-variable expressions
+  --> $DIR/syntax-errors.rs:27:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ index(1u32) } };
+   |                                 ^^^^^
+
+error: meta-variable expression parameter must be wrapped in parentheses
+  --> $DIR/syntax-errors.rs:32:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ count } };
+   |                                 ^^^^^
+
+error: meta-variable expression parameter must be wrapped in parentheses
+  --> $DIR/syntax-errors.rs:49:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ count{i} } };
+   |                                 ^^^^^
+
+error: expected identifier, found `123`
+  --> $DIR/syntax-errors.rs:54:23
+   |
+LL |     () => { ${ignore($123)} }
+   |                       ^^^ help: try removing `123`
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:66:19
+   |
+LL |         ${count() a b c}
+   |                   ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:66:19
+   |
+LL |         ${count() a b c}
+   |                   ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:68:20
+   |
+LL |         ${count($i a b c)}
+   |                    ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:68:20
+   |
+LL |         ${count($i a b c)}
+   |                    ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:70:23
+   |
+LL |         ${count($i, 1 a b c)}
+   |                       ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:70:23
+   |
+LL |         ${count($i, 1 a b c)}
+   |                       ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:72:21
+   |
+LL |         ${count($i) a b c}
+   |                     ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:72:21
+   |
+LL |         ${count($i) a b c}
+   |                     ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:75:22
+   |
+LL |         ${ignore($i) a b c}
+   |                      ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:75:22
+   |
+LL |         ${ignore($i) a b c}
+   |                      ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:77:21
+   |
+LL |         ${ignore($i a b c)}
+   |                     ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:77:21
+   |
+LL |         ${ignore($i a b c)}
+   |                     ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:80:19
+   |
+LL |         ${index() a b c}
+   |                   ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:80:19
+   |
+LL |         ${index() a b c}
+   |                   ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:82:19
+   |
+LL |         ${index(1 a b c)}
+   |                   ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:82:19
+   |
+LL |         ${index(1 a b c)}
+   |                   ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:85:19
+   |
+LL |         ${index() a b c}
+   |                   ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:85:19
+   |
+LL |         ${index() a b c}
+   |                   ^
+
+error: unexpected token: a
+  --> $DIR/syntax-errors.rs:87:19
+   |
+LL |         ${index(1 a b c)}
+   |                   ^
+   |
+note: meta-variable expression must not have trailing tokens
+  --> $DIR/syntax-errors.rs:87:19
+   |
+LL |         ${index(1 a b c)}
+   |                   ^
+
+error: meta-variable expression depth must be a literal
+  --> $DIR/syntax-errors.rs:94:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ index(IDX) } };
+   |                                 ^^^^^
+
+error: meta-variables within meta-variable expressions must be referenced using a dollar sign
+  --> $DIR/syntax-errors.rs:100:11
+   |
+LL |         ${count(foo)}
+   |           ^^^^^
+
+error: meta-variables within meta-variable expressions must be referenced using a dollar sign
+  --> $DIR/syntax-errors.rs:107:11
+   |
+LL |         ${ignore(bar)}
+   |           ^^^^^^
+
+error: unrecognized meta-variable expression
+  --> $DIR/syntax-errors.rs:113:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ aaaaaaaaaaaaaa(i) } };
+   |                                 ^^^^^^^^^^^^^^ help: supported expressions are count, ignore, index and len
+
+error: expected identifier or string literal
+  --> $DIR/syntax-errors.rs:38:14
+   |
+LL |     () => { ${} };
+   |              ^^
+
+error: expected identifier, found `"hi"`
+  --> $DIR/syntax-errors.rs:44:17
+   |
+LL |      () => { ${ "hi" } };
+   |                 ^^^^ help: try removing `"hi"`
+
+error: expected identifier or string literal
+  --> $DIR/syntax-errors.rs:60:33
+   |
+LL |     ( $( $i:ident ),* ) => { ${ {} } };
+   |                                 ^^
+
+error: aborting due to 25 previous errors
+

tests/ui/macros/metavar-expressions/usage-errors.rs

@@ -0,0 +1,55 @@
+// Errors for the `count` and `length` metavariable expressions
+
+#![feature(macro_metavar_expr)]
+
+// `curly` = Right hand side curly brackets
+// `no_rhs_dollar` = No dollar sign at the right hand side meta variable "function"
+// `round` = Left hand side round brackets
+
+macro_rules! curly__no_rhs_dollar__round {
+    ( $( $i:ident ),* ) => { ${ count($i) } };
+}
+const _: u32 = curly__no_rhs_dollar__round!(a, b, c);
+
+macro_rules! curly__no_rhs_dollar__no_round {
+    ( $i:ident ) => { ${ count($i) } };
+    //~^ ERROR `count` can not be placed inside the innermost repetition
+}
+curly__no_rhs_dollar__no_round!(a);
+
+macro_rules! curly__rhs_dollar__no_round {
+    ( $i:ident ) => { ${ count($i) } };
+    //~^ ERROR `count` can not be placed inside the innermost repetition
+}
+curly__rhs_dollar__no_round !(a);
+
+#[rustfmt::skip] // autoformatters can break a few of the error traces
+macro_rules! no_curly__no_rhs_dollar__round {
+    ( $( $i:ident ),* ) => { count(i) };
+    //~^ ERROR missing `fn` or `struct` for function or struct definition
+}
+no_curly__no_rhs_dollar__round !(a, b, c);
+
+#[rustfmt::skip] // autoformatters can break a few of the error traces
+macro_rules! no_curly__no_rhs_dollar__no_round {
+    ( $i:ident ) => { count(i) };
+    //~^ ERROR missing `fn` or `struct` for function or struct definition
+}
+no_curly__no_rhs_dollar__no_round !(a);
+
+#[rustfmt::skip] // autoformatters can break a few of the error traces
+macro_rules! no_curly__rhs_dollar__round {
+    ( $( $i:ident ),* ) => { count($i) };
+    //~^ ERROR variable `i` is still repeating at this depth
+}
+no_curly__rhs_dollar__round! (a);
+
+#[rustfmt::skip] // autoformatters can break a few of the error traces
+macro_rules! no_curly__rhs_dollar__no_round {
+    ( $i:ident ) => { count($i) };
+    //~^ ERROR cannot find function `count` in this scope
+}
+const _: u32 = no_curly__rhs_dollar__no_round! (a);
+//~^ ERROR cannot find value `a` in this scope
+
+fn main() {}

tests/ui/macros/metavar-expressions/usage-errors.stderr

@@ -0,0 +1,71 @@
+error: `count` can not be placed inside the innermost repetition
+  --> $DIR/usage-errors.rs:15:24
+   |
+LL |     ( $i:ident ) => { ${ count($i) } };
+   |                        ^^^^^^^^^^^^^
+
+error: `count` can not be placed inside the innermost repetition
+  --> $DIR/usage-errors.rs:21:24
+   |
+LL |     ( $i:ident ) => { ${ count($i) } };
+   |                        ^^^^^^^^^^^^^
+
+error: missing `fn` or `struct` for function or struct definition
+  --> $DIR/usage-errors.rs:28:30
+   |
+LL |     ( $( $i:ident ),* ) => { count(i) };
+   |                              ^^^^^
+...
+LL | no_curly__no_rhs_dollar__round !(a, b, c);
+   | ----------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `no_curly__no_rhs_dollar__round` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: if you meant to call a macro, try
+   |
+LL |     ( $( $i:ident ),* ) => { count!(i) };
+   |                                   +
+
+error: missing `fn` or `struct` for function or struct definition
+  --> $DIR/usage-errors.rs:35:23
+   |
+LL |     ( $i:ident ) => { count(i) };
+   |                       ^^^^^
+...
+LL | no_curly__no_rhs_dollar__no_round !(a);
+   | -------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `no_curly__no_rhs_dollar__no_round` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: if you meant to call a macro, try
+   |
+LL |     ( $i:ident ) => { count!(i) };
+   |                            +
+
+error: variable `i` is still repeating at this depth
+  --> $DIR/usage-errors.rs:42:36
+   |
+LL |     ( $( $i:ident ),* ) => { count($i) };
+   |                                    ^^
+
+error[E0425]: cannot find value `a` in this scope
+  --> $DIR/usage-errors.rs:52:49
+   |
+LL |     ( $i:ident ) => { count($i) };
+   |                             -- due to this macro variable
+...
+LL | const _: u32 = no_curly__rhs_dollar__no_round! (a);
+   |                                                 ^ not found in this scope
+
+error[E0425]: cannot find function `count` in this scope
+  --> $DIR/usage-errors.rs:49:23
+   |
+LL |     ( $i:ident ) => { count($i) };
+   |                       ^^^^^ not found in this scope
+...
+LL | const _: u32 = no_curly__rhs_dollar__no_round! (a);
+   |                ----------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `no_curly__rhs_dollar__no_round` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 7 previous errors
+
+For more information about this error, try `rustc --explain E0425`.

tests/ui/macros/rfc-3086-metavar-expr/syntax-errors.rs

@@ -1,164 +0,0 @@
-#![feature(macro_metavar_expr)]
-
-// `curly` = Right hand side curly brackets
-// `no_rhs_dollar` = No dollar sign at the right hand side meta variable "function"
-// `round` = Left hand side round brackets
-
-macro_rules! curly__no_rhs_dollar__round {
-    ( $( $i:ident ),* ) => { ${ count($i) } };
-}
-
-macro_rules! curly__no_rhs_dollar__no_round {
-    ( $i:ident ) => { ${ count($i) } };
-    //~^ ERROR `count` can not be placed inside the innermost repetition
-}
-
-macro_rules! curly__rhs_dollar__no_round {
-    ( $i:ident ) => { ${ count($i) } };
-    //~^ ERROR `count` can not be placed inside the innermost repetition
-}
-
-#[rustfmt::skip] // autoformatters can break a few of the error traces
-macro_rules! no_curly__no_rhs_dollar__round {
-    ( $( $i:ident ),* ) => { count(i) };
-    //~^ ERROR cannot find function `count` in this scope
-    //~| ERROR cannot find value `i` in this scope
-}
-
-#[rustfmt::skip] // autoformatters can break a few of the error traces
-macro_rules! no_curly__no_rhs_dollar__no_round {
-    ( $i:ident ) => { count(i) };
-    //~^ ERROR cannot find function `count` in this scope
-    //~| ERROR cannot find value `i` in this scope
-}
-
-#[rustfmt::skip] // autoformatters can break a few of the error traces
-macro_rules! no_curly__rhs_dollar__round {
-    ( $( $i:ident ),* ) => { count($i) };
-    //~^ ERROR variable `i` is still repeating at this depth
-}
-
-#[rustfmt::skip] // autoformatters can break a few of the error traces
-macro_rules! no_curly__rhs_dollar__no_round {
-    ( $i:ident ) => { count($i) };
-    //~^ ERROR cannot find function `count` in this scope
-}
-
-// Other scenarios
-
-macro_rules! dollar_dollar_in_the_lhs {
-    ( $$ $a:ident ) => {
-        //~^ ERROR unexpected token: $
-    };
-}
-
-macro_rules! extra_garbage_after_metavar {
-    ( $( $i:ident ),* ) => {
-        ${count() a b c}
-        //~^ ERROR unexpected token: a
-        //~| ERROR expected expression, found `$`
-        ${count($i a b c)}
-        //~^ ERROR unexpected token: a
-        ${count($i, 1 a b c)}
-        //~^ ERROR unexpected token: a
-        ${count($i) a b c}
-        //~^ ERROR unexpected token: a
-
-        ${ignore($i) a b c}
-        //~^ ERROR unexpected token: a
-        ${ignore($i a b c)}
-        //~^ ERROR unexpected token: a
-
-        ${index() a b c}
-        //~^ ERROR unexpected token: a
-        ${index(1 a b c)}
-        //~^ ERROR unexpected token: a
-
-        ${index() a b c}
-        //~^ ERROR unexpected token: a
-        ${index(1 a b c)}
-        //~^ ERROR unexpected token: a
-    };
-}
-
-const IDX: usize = 1;
-macro_rules! metavar_depth_is_not_literal {
-    ( $( $i:ident ),* ) => { ${ index(IDX) } };
-    //~^ ERROR meta-variable expression depth must be a literal
-    //~| ERROR expected expression, found `$`
-}
-
-macro_rules! metavar_in_the_lhs {
-    ( ${ len() } ) => {
-        //~^ ERROR unexpected token: {
-        //~| ERROR expected one of: `*`, `+`, or `?`
-    };
-}
-
-macro_rules! metavar_token_without_ident {
-    ( $( $i:ident ),* ) => { ${ ignore() } };
-    //~^ ERROR meta-variable expressions must be referenced using a dollar sign
-    //~| ERROR expected expression
-}
-
-macro_rules! metavar_with_literal_suffix {
-    ( $( $i:ident ),* ) => { ${ index(1u32) } };
-    //~^ ERROR only unsuffixes integer literals are supported in meta-variable expressions
-    //~| ERROR expected expression, found `$`
-}
-
-macro_rules! metavar_without_parens {
-    ( $( $i:ident ),* ) => { ${ count{i} } };
-    //~^ ERROR meta-variable expression parameter must be wrapped in parentheses
-    //~| ERROR expected expression, found `$`
-}
-
-#[rustfmt::skip]
-macro_rules! open_brackets_without_tokens {
-    ( $( $i:ident ),* ) => { ${ {} } };
-    //~^ ERROR expected expression, found `$`
-    //~| ERROR expected identifier
-}
-
-macro_rules! unknown_count_ident {
-    ( $( $i:ident )* ) => {
-        ${count(foo)}
-        //~^ ERROR meta-variable expressions must be referenced using a dollar sign
-        //~| ERROR expected expression
-    };
-}
-
-macro_rules! unknown_ignore_ident {
-    ( $( $i:ident )* ) => {
-        ${ignore(bar)}
-        //~^ ERROR meta-variable expressions must be referenced using a dollar sign
-        //~| ERROR expected expression
-    };
-}
-
-macro_rules! unknown_metavar {
-    ( $( $i:ident ),* ) => { ${ aaaaaaaaaaaaaa(i) } };
-    //~^ ERROR unrecognized meta-variable expression
-    //~| ERROR expected expression
-}
-
-fn main() {
-    curly__no_rhs_dollar__round!(a, b, c);
-    curly__no_rhs_dollar__no_round!(a);
-    curly__rhs_dollar__no_round!(a);
-    no_curly__no_rhs_dollar__round!(a, b, c);
-    no_curly__no_rhs_dollar__no_round!(a);
-    no_curly__rhs_dollar__round!(a, b, c);
-    no_curly__rhs_dollar__no_round!(a);
-    //~^ ERROR cannot find value `a` in this scope
-
-    extra_garbage_after_metavar!(a);
-    metavar_depth_is_not_literal!(a);
-    metavar_token_without_ident!(a);
-    metavar_with_literal_suffix!(a);
-    metavar_without_parens!(a);
-    open_brackets_without_tokens!(a);
-    unknown_count_ident!(a);
-    unknown_ignore_ident!(a);
-    unknown_metavar!(a);
-}

tests/ui/macros/rfc-3086-metavar-expr/syntax-errors.stderr

@@ -1,382 +0,0 @@
-error: unexpected token: $
-  --> $DIR/syntax-errors.rs:50:8
-   |
-LL |     ( $$ $a:ident ) => {
-   |        ^
-
-note: `$$` and meta-variable expressions are not allowed inside macro parameter definitions
-  --> $DIR/syntax-errors.rs:50:8
-   |
-LL |     ( $$ $a:ident ) => {
-   |        ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:57:19
-   |
-LL |         ${count() a b c}
-   |                   ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:57:19
-   |
-LL |         ${count() a b c}
-   |                   ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:60:20
-   |
-LL |         ${count($i a b c)}
-   |                    ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:60:20
-   |
-LL |         ${count($i a b c)}
-   |                    ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:62:23
-   |
-LL |         ${count($i, 1 a b c)}
-   |                       ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:62:23
-   |
-LL |         ${count($i, 1 a b c)}
-   |                       ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:64:21
-   |
-LL |         ${count($i) a b c}
-   |                     ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:64:21
-   |
-LL |         ${count($i) a b c}
-   |                     ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:67:22
-   |
-LL |         ${ignore($i) a b c}
-   |                      ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:67:22
-   |
-LL |         ${ignore($i) a b c}
-   |                      ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:69:21
-   |
-LL |         ${ignore($i a b c)}
-   |                     ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:69:21
-   |
-LL |         ${ignore($i a b c)}
-   |                     ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:72:19
-   |
-LL |         ${index() a b c}
-   |                   ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:72:19
-   |
-LL |         ${index() a b c}
-   |                   ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:74:19
-   |
-LL |         ${index(1 a b c)}
-   |                   ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:74:19
-   |
-LL |         ${index(1 a b c)}
-   |                   ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:77:19
-   |
-LL |         ${index() a b c}
-   |                   ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:77:19
-   |
-LL |         ${index() a b c}
-   |                   ^
-
-error: unexpected token: a
-  --> $DIR/syntax-errors.rs:79:19
-   |
-LL |         ${index(1 a b c)}
-   |                   ^
-   |
-note: meta-variable expression must not have trailing tokens
-  --> $DIR/syntax-errors.rs:79:19
-   |
-LL |         ${index(1 a b c)}
-   |                   ^
-
-error: meta-variable expression depth must be a literal
-  --> $DIR/syntax-errors.rs:86:33
-   |
-LL |     ( $( $i:ident ),* ) => { ${ index(IDX) } };
-   |                                 ^^^^^
-
-error: unexpected token: {
-  --> $DIR/syntax-errors.rs:92:8
-   |
-LL |     ( ${ len() } ) => {
-   |        ^^^^^^^^^
-
-note: `$$` and meta-variable expressions are not allowed inside macro parameter definitions
-  --> $DIR/syntax-errors.rs:92:8
-   |
-LL |     ( ${ len() } ) => {
-   |        ^^^^^^^^^
-
-error: expected one of: `*`, `+`, or `?`
-  --> $DIR/syntax-errors.rs:92:8
-   |
-LL |     ( ${ len() } ) => {
-   |        ^^^^^^^^^
-
-error: meta-variables within meta-variable expressions must be referenced using a dollar sign
-  --> $DIR/syntax-errors.rs:99:33
-   |
-LL |     ( $( $i:ident ),* ) => { ${ ignore() } };
-   |                                 ^^^^^^
-
-error: only unsuffixes integer literals are supported in meta-variable expressions
-  --> $DIR/syntax-errors.rs:105:33
-   |
-LL |     ( $( $i:ident ),* ) => { ${ index(1u32) } };
-   |                                 ^^^^^
-
-error: meta-variable expression parameter must be wrapped in parentheses
-  --> $DIR/syntax-errors.rs:111:33
-   |
-LL |     ( $( $i:ident ),* ) => { ${ count{i} } };
-   |                                 ^^^^^
-
-error: meta-variables within meta-variable expressions must be referenced using a dollar sign
-  --> $DIR/syntax-errors.rs:125:11
-   |
-LL |         ${count(foo)}
-   |           ^^^^^
-
-error: meta-variables within meta-variable expressions must be referenced using a dollar sign
-  --> $DIR/syntax-errors.rs:133:11
-   |
-LL |         ${ignore(bar)}
-   |           ^^^^^^
-
-error: unrecognized meta-variable expression
-  --> $DIR/syntax-errors.rs:140:33
-   |
-LL |     ( $( $i:ident ),* ) => { ${ aaaaaaaaaaaaaa(i) } };
-   |                                 ^^^^^^^^^^^^^^ help: supported expressions are count, ignore, index and len
-
-error: expected identifier or string literal
-  --> $DIR/syntax-errors.rs:118:33
-   |
-LL |     ( $( $i:ident ),* ) => { ${ {} } };
-   |                                 ^^
-
-error: `count` can not be placed inside the innermost repetition
-  --> $DIR/syntax-errors.rs:12:24
-   |
-LL |     ( $i:ident ) => { ${ count($i) } };
-   |                        ^^^^^^^^^^^^^
-
-error: `count` can not be placed inside the innermost repetition
-  --> $DIR/syntax-errors.rs:17:24
-   |
-LL |     ( $i:ident ) => { ${ count($i) } };
-   |                        ^^^^^^^^^^^^^
-
-error: variable `i` is still repeating at this depth
-  --> $DIR/syntax-errors.rs:37:36
-   |
-LL |     ( $( $i:ident ),* ) => { count($i) };
-   |                                    ^^
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:57:9
-   |
-LL |         ${count() a b c}
-   |         ^ expected expression
-...
-LL |     extra_garbage_after_metavar!(a);
-   |     ------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `extra_garbage_after_metavar` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:86:30
-   |
-LL |     ( $( $i:ident ),* ) => { ${ index(IDX) } };
-   |                              ^ expected expression
-...
-LL |     metavar_depth_is_not_literal!(a);
-   |     -------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `metavar_depth_is_not_literal` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:99:30
-   |
-LL |     ( $( $i:ident ),* ) => { ${ ignore() } };
-   |                              ^ expected expression
-...
-LL |     metavar_token_without_ident!(a);
-   |     ------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `metavar_token_without_ident` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:105:30
-   |
-LL |     ( $( $i:ident ),* ) => { ${ index(1u32) } };
-   |                              ^ expected expression
-...
-LL |     metavar_with_literal_suffix!(a);
-   |     ------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `metavar_with_literal_suffix` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:111:30
-   |
-LL |     ( $( $i:ident ),* ) => { ${ count{i} } };
-   |                              ^ expected expression
-...
-LL |     metavar_without_parens!(a);
-   |     -------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `metavar_without_parens` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:118:30
-   |
-LL |     ( $( $i:ident ),* ) => { ${ {} } };
-   |                              ^ expected expression
-...
-LL |     open_brackets_without_tokens!(a);
-   |     -------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `open_brackets_without_tokens` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:125:9
-   |
-LL |         ${count(foo)}
-   |         ^ expected expression
-...
-LL |     unknown_count_ident!(a);
-   |     ----------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `unknown_count_ident` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:133:9
-   |
-LL |         ${ignore(bar)}
-   |         ^ expected expression
-...
-LL |     unknown_ignore_ident!(a);
-   |     ------------------------ in this macro invocation
-   |
-   = note: this error originates in the macro `unknown_ignore_ident` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: expected expression, found `$`
-  --> $DIR/syntax-errors.rs:140:30
-   |
-LL |     ( $( $i:ident ),* ) => { ${ aaaaaaaaaaaaaa(i) } };
-   |                              ^ expected expression
-...
-LL |     unknown_metavar!(a);
-   |     ------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `unknown_metavar` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0425]: cannot find value `i` in this scope
-  --> $DIR/syntax-errors.rs:23:36
-   |
-LL |     ( $( $i:ident ),* ) => { count(i) };
-   |                                    ^ not found in this scope
-...
-LL |     no_curly__no_rhs_dollar__round!(a, b, c);
-   |     ---------------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `no_curly__no_rhs_dollar__round` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0425]: cannot find value `i` in this scope
-  --> $DIR/syntax-errors.rs:30:29
-   |
-LL |     ( $i:ident ) => { count(i) };
-   |                             ^ not found in this scope
-...
-LL |     no_curly__no_rhs_dollar__no_round!(a);
-   |     ------------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `no_curly__no_rhs_dollar__no_round` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0425]: cannot find value `a` in this scope
-  --> $DIR/syntax-errors.rs:152:37
-   |
-LL |     ( $i:ident ) => { count($i) };
-   |                             -- due to this macro variable
-...
-LL |     no_curly__rhs_dollar__no_round!(a);
-   |                                     ^ not found in this scope
-
-error[E0425]: cannot find function `count` in this scope
-  --> $DIR/syntax-errors.rs:23:30
-   |
-LL |     ( $( $i:ident ),* ) => { count(i) };
-   |                              ^^^^^ not found in this scope
-...
-LL |     no_curly__no_rhs_dollar__round!(a, b, c);
-   |     ---------------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `no_curly__no_rhs_dollar__round` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0425]: cannot find function `count` in this scope
-  --> $DIR/syntax-errors.rs:30:23
-   |
-LL |     ( $i:ident ) => { count(i) };
-   |                       ^^^^^ not found in this scope
-...
-LL |     no_curly__no_rhs_dollar__no_round!(a);
-   |     ------------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `no_curly__no_rhs_dollar__no_round` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0425]: cannot find function `count` in this scope
-  --> $DIR/syntax-errors.rs:43:23
-   |
-LL |     ( $i:ident ) => { count($i) };
-   |                       ^^^^^ not found in this scope
-...
-LL |     no_curly__rhs_dollar__no_round!(a);
-   |     ---------------------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `no_curly__rhs_dollar__no_round` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: aborting due to 39 previous errors
-
-For more information about this error, try `rustc --explain E0425`.