Changes

Update parser and adapt to the new Tpoly invariant. Requires bootstrap.

The argument of a Tarrow must now be a [Tpoly] node.
 (commit: 94908d2)

bootstrap
 (commit: fbca0ab)

Add tests for polymorphic parameters
 (commit: a664599)

Promote polymorphic parameters tests failures
 (commit: c39e29d)

Refactor: more descriptive return type for [split_function], renaming and comment work
 (commit: 489e219)

Introduce new error "opt params cannot be polymorphic"
 (commit: da0cabe)

Wrap and generalize filter_arrow_mono if principal
 (commit: ba14d13)

Handle polymorphic parameters in type_apply_arg
 (commit: 24b6f4c)

Refactor Pexp_function case and handle poly
 (commit: 16d8e49)

Add one generalization level in type_class_arg_pattern
 (commit: e882d5a)

Handle polymorphic parameters in [type_approx and] [type_pat_aux]
 (commit: ac9691a)

Add changes entry for #15733
 (commit: 6e02745)

Add test with class argument
 (commit: d31142a)

Additional tests with labels
 (commit: 2ad84dc)

review: reorder functions in btype
 (commit: f401ccf)

review: comment format
 (commit: ced4529)

review: add a Btype.newgenmono utility symetrical to Ctype.newmono
 (commit: b6629c6)

review: use label names in error messages
 (commit: 6fc24f4)

review: additional tests
 (commit: 2dd9b7d)

Add test for polymorphic variants in polymorphic parameters
 (commit: 669bd47)

Take fixed instances of polys where appropriate

This fixes a bug in the interaction between polymorphic variants and polymorphic
parameters. The actual bug fix is just changing two falses to trues but I also
changed the instance_poly interface to make similar mistakes less likely to
happen.
 (commit: e93ba21)

Show issue with subtyping trace
 (commit: 74b9f1f)

Fix subtyping error trace
 (commit: 4e597e9)

tests: Promote error messages improvements after rebasing.
 (commit: e6d2834)

review: more reuse in parser and reloc in [param_type]
 (commit: be3016c)

review: move [is_really_poly] utility to Ctype.
 (commit: a5dc2ad)

Add more test cases
 (commit: 47350a7)

Move definition closer to usage
 (commit: 19c9abe)

Additional test cases
 (commit: c5587a4)

Document function in comment
 (commit: c9a8533)

Add test cases
 (commit: 21b3641)

Fix typo in error message
 (commit: 7cde513)

Rename function and move it to Btype
 (commit: e8eb592)

Inline function and exception used only once
 (commit: d01ee5f)

Document function
 (commit: 1dcf986)

Enforce Tpoly invariant
 (commit: 7d2f412)

Clarify conditions
 (commit: ad0db61)

Clearer argument label and field names
 (commit: 730e704)

Turn ordinary comment into a documentation comment
 (commit: ba7bf49)

Clearer variable name
 (commit: 1e1c51e)

Fix wrong set of univars
 (commit: 73934de)

review: De-duplicate parser rule for let
 (commit: 7202cde)

review: Add test with syntactic arity mismatch
 (commit: 6e7a744)

review: Fix test
 (commit: f3d08a2)