error: mismatched closing delimiter: `)`
  --> $DIR/issue-102878.rs:1:35
   |
LL | macro_rules!test{($l:expr,$_:r)=>({const:y y)}
   |                                  -^         ^ mismatched closing delimiter
   |                                  ||
   |                                  |unclosed delimiter
   |                                  closing delimiter possibly meant for this

error: invalid fragment specifier `r`
  --> $DIR/issue-102878.rs:1:27
   |
LL | macro_rules!test{($l:expr,$_:r)=>({const:y y)}
   |                           ^^^^
   |
   = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, `item` and `vis`

error: expected identifier, found keyword `const`
  --> $DIR/issue-102878.rs:1:36
   |
LL | macro_rules!test{($l:expr,$_:r)=>({const:y y)}
   |                                    ^^^^^ expected identifier, found keyword
...
LL | fn s(){test!(1,i)}
   |        ---------- in this macro invocation
   |
   = note: this error originates in the macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)
help: escape `const` to use it as an identifier
   |
LL | macro_rules!test{($l:expr,$_:r)=>({r#const:y y)}
   |                                    ++

error: expected identifier, found keyword `const`
  --> $DIR/issue-102878.rs:1:36
   |
LL | macro_rules!test{($l:expr,$_:r)=>({const:y y)}
   |                                    ^^^^^ expected identifier, found keyword
...
LL | fn s(){test!(1,i)}
   |        ---------- in this macro invocation
   |
   = note: this error originates in the macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)
help: escape `const` to use it as an identifier
   |
LL | macro_rules!test{($l:expr,$_:r)=>({r#const:y y)}
   |                                    ++

error: expected identifier, found `:`
  --> $DIR/issue-102878.rs:1:41
   |
LL | macro_rules!test{($l:expr,$_:r)=>({const:y y)}
   |                                         ^ expected identifier
...
LL | fn s(){test!(1,i)}
   |        ---------- in this macro invocation
   |
   = note: this error originates in the macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 5 previous errors