An important part of the interface of a function is the parameter names,
for making used of named arguments. This PR makes the parameter names
print in a reliable way. The parameters of the type now appear as
hygienic names if they cannot be used as named arguments.
Modifies the heuristic for how parameters are chosen to appear before or
after the colon. The rule is now that parameters start appearing after
the colon at the first non-dependent non-instance-implicit parameter
that has a name unusable as a named argument. This is a refinement of
#2846.
Fixes the issue where consecutive hygienic names pretty print without a
space separating them, so we now have `(x✝ y✝ : Nat)` rather than `(x✝y✝
: Nat)`.
Breaking change: `Lean.PrettyPrinter.Formatter.pushToken` now takes an
additional boolean `ident` argument, which should be `true` for
identifiers. Used to insert discretionary space between consecutive
identifiers.
Closes#5810
The formatter was using `tk ++ " "` to separate tokens from tokens they
would merge with, but `" "` is not whitespace that could merge. This
affected large binder lists, which wouldn't pretty print with any line
breaks. Now they can be flowed across multiple lines.
Closes#5424
