error: expected type, found `{`
  --> $DIR/macro-fail.rs:31:27
   |
LL | fn make_marker() -> impl Marker<gimme_a_const!(marker)> {
   |                                 ----------------------
   |                                 |
   |                                 this macro call doesn't expand to a type
   |                                 in this macro invocation
...
LL |       ($rusty: ident) => {{ let $rusty = 3; *&$rusty }}
   |                           ^ expected type
   |
   = note: this error originates in the macro `gimme_a_const` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected type, found `{`
  --> $DIR/macro-fail.rs:31:27
   |
LL |   Example::<gimme_a_const!(marker)>
   |             ----------------------
   |             |
   |             this macro call doesn't expand to a type
   |             in this macro invocation
...
LL |       ($rusty: ident) => {{ let $rusty = 3; *&$rusty }}
   |                           ^ expected type
   |
   = note: this error originates in the macro `gimme_a_const` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected type, found `{`
  --> $DIR/macro-fail.rs:4:10
   |
LL |   () => {{
   |          ^ expected type
...
LL |   let _fail = Example::<external_macro!()>;
   |                         -----------------
   |                         |
   |                         this macro call doesn't expand to a type
   |                         in this macro invocation
   |
   = note: this error originates in the macro `external_macro` (in Nightly builds, run with -Z macro-backtrace for more info)

error: unexpected end of macro invocation
  --> $DIR/macro-fail.rs:42:25
   |
LL |     macro_rules! gimme_a_const {
   |     -------------------------- when calling this macro
...
LL |   let _fail = Example::<gimme_a_const!()>;
   |                         ^^^^^^^^^^^^^^^^ missing tokens in macro arguments
   |
note: while trying to match meta-variable `$rusty:ident`
  --> $DIR/macro-fail.rs:31:8
   |
LL |       ($rusty: ident) => {{ let $rusty = 3; *&$rusty }}
   |        ^^^^^^^^^^^^^

error[E0747]: type provided when a constant was expected
  --> $DIR/macro-fail.rs:14:33
   |
LL | fn make_marker() -> impl Marker<gimme_a_const!(marker)> {
   |                                 ^^^^^^^^^^^^^^^^^^^^^^

error[E0747]: type provided when a constant was expected
  --> $DIR/macro-fail.rs:14:33
   |
LL | fn make_marker() -> impl Marker<gimme_a_const!(marker)> {
   |                                 ^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error[E0747]: type provided when a constant was expected
  --> $DIR/macro-fail.rs:17:13
   |
LL |   Example::<gimme_a_const!(marker)>
   |             ^^^^^^^^^^^^^^^^^^^^^^

error[E0284]: type annotations needed
  --> $DIR/macro-fail.rs:17:3
   |
LL |   Example::<gimme_a_const!(marker)>
   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer the value of the const parameter `N` declared on the struct `Example`
   |
note: required by a const generic parameter in `Example`
  --> $DIR/macro-fail.rs:1:16
   |
LL | struct Example<const N: usize>;
   |                ^^^^^^^^^^^^^^ required by this const generic parameter in `Example`

error[E0747]: type provided when a constant was expected
  --> $DIR/macro-fail.rs:38:25
   |
LL |   let _fail = Example::<external_macro!()>;
   |                         ^^^^^^^^^^^^^^^^^

error[E0747]: type provided when a constant was expected
  --> $DIR/macro-fail.rs:42:25
   |
LL |   let _fail = Example::<gimme_a_const!()>;
   |                         ^^^^^^^^^^^^^^^^

error[E0284]: type annotations needed for `Example<_>`
  --> $DIR/macro-fail.rs:38:7
   |
LL |   let _fail = Example::<external_macro!()>;
   |       ^^^^^   ---------------------------- type must be known at this point
   |
note: required by a const generic parameter in `Example`
  --> $DIR/macro-fail.rs:1:16
   |
LL | struct Example<const N: usize>;
   |                ^^^^^^^^^^^^^^ required by this const generic parameter in `Example`
help: consider giving `_fail` an explicit type, where the value of const parameter `N` is specified
   |
LL |   let _fail: Example<N> = Example::<external_macro!()>;
   |            ++++++++++++

error[E0284]: type annotations needed for `Example<_>`
  --> $DIR/macro-fail.rs:42:7
   |
LL |   let _fail = Example::<gimme_a_const!()>;
   |       ^^^^^   --------------------------- type must be known at this point
   |
note: required by a const generic parameter in `Example`
  --> $DIR/macro-fail.rs:1:16
   |
LL | struct Example<const N: usize>;
   |                ^^^^^^^^^^^^^^ required by this const generic parameter in `Example`
help: consider giving `_fail` an explicit type, where the value of const parameter `N` is specified
   |
LL |   let _fail: Example<N> = Example::<gimme_a_const!()>;
   |            ++++++++++++

error: aborting due to 12 previous errors

Some errors have detailed explanations: E0284, E0747.
For more information about an error, try `rustc --explain E0284`.