PEP 695: Incorporated recent feedback from python-dev. (#2713)

Co-authored-by: Eric Traut <[email protected]>

Author: erictraut

pep-0695.rst

@@ -754,6 +754,30 @@ were less clear. Also, this syntax did not interact well with class and
 function decorators, which are common in Python. Only one other popular
 programming language, C++, uses this approach.
 
+We likewise considered prefix forms that looked like decorators (e.g.,
+``@using(S, T)``). This idea was rejected because such forms would be confused
+with regular decorators, and they would not compose well with existing
+decorators. Furthermore, decorators are logically executed after the statement
+they are decorating, so it would be confusing for them to introduce symbols
+(type parameters) that are visible within the "decorated" statement, which is
+logically executed before the decorator itself.
+
+
+Angle Brackets
+--------------
+Many languages that support generics make use of angle brackets. (Refer to
+the table at the end of Appendix A for a summary.) We explored the use of
+angle brackets for type parameter declarations in Python, but we ultimately
+rejected it for two reasons. First, angle brackets are not considered
+"paired" by the Python scanner, so end-of-line characters between a ``<``
+and ``>`` token are retained. That means any line breaks within a list of
+type parameters would require the use of unsightly and cumbersome ``\`` escape
+sequences. Second, Python has already established the use of square brackets
+for explicit specialization of a generic type (e.g., ``list[int]``). We
+concluded that it would be inconsistent and confusing to use angle brackets
+for generic declarations but square brackets for explicit specialization. All
+other languages that we surveyed were consistent in this regard.
+
 
 Bounds Syntax
 -------------
@@ -1043,7 +1067,7 @@ Rust uses declaration-site variance, and variance of type parameters is
 typically inferred from their usage. In cases where a type parameter is not
 used within a type, variance can be specified explicitly.
 
-Rust provides no way to specify a default type argument.
+A default type argument can be specified using the "=" operator.
 
 ::
 
@@ -1149,7 +1173,7 @@ Summary
 +------------+----------+---------+--------+----------+-----------+-----------+
 | Swift      | <>       | T: X    |        |          | decl      | inferred  |
 +------------+----------+---------+--------+----------+-----------+-----------+
-| Rust       | <>       | T: X,   |        |          | decl      | inferred, |
+| Rust       | <>       | T: X,   |        | =        | decl      | inferred, |
 |            |          | where   |        |          |           | explicit  |
 +------------+----------+---------+--------+----------+-----------+-----------+
 | Kotlin     | <>       | T: X    |        |          | use, decl | inferred  |