expandable 0.1.1

What if we could check declarative macros before using them?
Documentation 
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error: Potentially invalid expansion. Expected an expression, an identifier, `::`, `<`, `Self`, `break` or 14 others.
 --> tests/ui/fail/expr-tuple.rs:6:10
  |
6 |         (,)
  |          ^

error: Potentially invalid expansion. Expected an expression, an identifier, `::`, `<`, `Self`, `break` or 14 others.
  --> tests/ui/fail/expr-tuple.rs:13:13
   |
13 |         (42,, 42)
   |             ^

error: Potentially invalid expansion. Expected `!=`, `!`, `%`, `&&`, `&`, `*` or 21 others.
  --> tests/ui/fail/expr-tuple.rs:20:12
   |
20 |         (a b)
   |            ^