document ; vs , for generic params (#17192)

doc/manual.rst

@@ -4805,7 +4805,6 @@ The following example shows how a generic binary tree can be modeled:
 The ``T`` is called a `generic type parameter`:idx: or
 a `type variable`:idx:.
 
-
 Is operator
 -----------
 
@@ -4861,6 +4860,12 @@ more complex type classes:
     for key, value in fieldPairs(rec):
       echo key, " = ", value
 
+Type constraints on generic parameters can be grouped with `,` and propagation
+stops with `;`, similarly to parameters for macros and templates:
+
+.. code-block:: nim
+  proc fn1[T; U, V: SomeFloat]() = discard # T is unconstrained
+  template fn2(t; u, v: SomeFloat) = discard # t is unconstrained
 
 Whilst the syntax of type classes appears to resemble that of ADTs/algebraic data
 types in ML-like languages, it should be understood that type classes are static