Account for type params on method without parentheses

[estebank]

Account for those type parameters in the structured suggestion when forgetting to call method:

error[E0615]: attempted to take value of method `collect` on type `std::vec::IntoIter<_>`
  --> $DIR/method-missing-parentheses.rs:2:32
   |
LL |     let _ = vec![].into_iter().collect::<usize>;
   |                                ^^^^^^^---------
   |                                |
   |                                help: use parentheses to call the method: `collect::<usize>()`

[rust-highfive]

r? @davidtwco

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[estebank]

The second commit can be reverted if it is too intrusive for too small a gain.

[petrochenkov]

Looks like the second comment also makes fields with generic arguments legal under #[cfg(FALSE)], which is a language change.

[estebank]

@petrochenkov adding delay_span_bug would help with accidental stabilization, but not be a good experience. Is there a place where this check could be done even if cfged out?

[estebank]

@bors r=davidtwco

[bors]

📌 Commit 9d91489 has been approved by davidtwco