error: `cfg` is not followed by parentheses
  --> $DIR/cfg-attr-syntax-validation.rs:1:1
   |
LL | #[cfg]
   | ^^^^^^ help: expected syntax is: `cfg(/* predicate */)`

error: `cfg` is not followed by parentheses
  --> $DIR/cfg-attr-syntax-validation.rs:4:1
   |
LL | #[cfg = 10]
   | ^^^^^^^^^^^ help: expected syntax is: `cfg(/* predicate */)`

error: `cfg` predicate is not specified
  --> $DIR/cfg-attr-syntax-validation.rs:7:1
   |
LL | #[cfg()]
   | ^^^^^^^^ help: expected syntax is: `cfg(/* predicate */)`

error: multiple `cfg` predicates are specified
  --> $DIR/cfg-attr-syntax-validation.rs:10:10
   |
LL | #[cfg(a, b)]
   |          ^

error: `cfg` predicate key cannot be a literal
  --> $DIR/cfg-attr-syntax-validation.rs:13:7
   |
LL | #[cfg("str")]
   |       ^^^^^

error: `cfg` predicate key must be an identifier
  --> $DIR/cfg-attr-syntax-validation.rs:16:7
   |
LL | #[cfg(a::b)]
   |       ^^^^

error[E0537]: invalid predicate `a`
  --> $DIR/cfg-attr-syntax-validation.rs:19:7
   |
LL | #[cfg(a())]
   |       ^^^

error[E0565]: literal in `cfg` predicate value must be a string
  --> $DIR/cfg-attr-syntax-validation.rs:22:11
   |
LL | #[cfg(a = 10)]
   |           ^^

error[E0565]: literal in `cfg` predicate value must be a string
  --> $DIR/cfg-attr-syntax-validation.rs:25:11
   |
LL | #[cfg(a = b"hi")]
   |           -^^^^
   |           |
   |           help: consider removing the prefix

error: expected unsuffixed literal or identifier, found `concat!("nonexistent")`
  --> $DIR/cfg-attr-syntax-validation.rs:30:25
   |
LL |         #[cfg(feature = $expr)]
   |                         ^^^^^
...
LL | generate_s10!(concat!("nonexistent"));
   | ------------------------------------- in this macro invocation
   |
   = note: this error originates in the macro `generate_s10` (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected unsuffixed literal or identifier, found `concat!("nonexistent")`
  --> $DIR/cfg-attr-syntax-validation.rs:30:25
   |
LL |         #[cfg(feature = $expr)]
   |                         ^^^^^
...
LL | generate_s10!(concat!("nonexistent"));
   | ------------------------------------- in this macro invocation
   |
   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
   = note: this error originates in the macro `generate_s10` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 11 previous errors

Some errors have detailed explanations: E0537, E0565.
For more information about an error, try `rustc --explain E0537`.