Incorporate tech review from Slava

Co-authored-by: Slava Pestov <[email protected]>

Author: amartini51

TSPL.docc/LanguageGuide/Generics.md

@@ -291,9 +291,16 @@ like `T` and `MyTypeParameter`,
 to indicate that they're a placeholder for a *type*, not a value.
 
 > Note:
-> If you don't need to name a type parameter or give it any constraints,
+> If you don't need to name a type parameter
+> and its generic type constraints are simple,
 > there's an alternate, lightweight syntax you can use instead,
 > as described in <doc:OpaqueTypes#Opaque-Parameter-Types>.
+<!--
+Comparison between this syntax and the lightweight syntax
+is in the Opaque Types chapter, not here ---
+the reader hasn't learned about constraints yet,
+so it wouldn't make sense to list what is/isn't supported.
+-->
 
 ## Generic Types
 

TSPL.docc/LanguageGuide/OpaqueTypes.md

@@ -945,8 +945,8 @@ func drawTwiceSome(_ shape: some Shape) -> String {
 ```
 
 The `drawTwiceGeneric(_:)` function
-uses a generic type parameter named `SomeShape`,
-and explicitly includes the protocol conformance requirement.
+declares a generic type parameter named `SomeShape`,
+with a constraint that requires `SomeShape` to conform to the `Shape` protocol.
 The `drawTwiceSome(_:)` function
 uses the type `some Shape` for its argument.
 This creates a new, unnamed, generic type parameter for the function
@@ -973,10 +973,14 @@ but there's no constraint that requires them to be the same type.
 When you call `combine(shape:with)`,
 you can pass two different shapes ---
 in this case, one triangle and one trapezoid.
-If you need to write a function
-that has multiple generic parameters
-and constrain them to be are all the same type,
-use the usual generic syntax instead.
+
+Unlike the syntax for named generic type parameters,
+described in <docc:Generics> chapter,
+this lightweight syntax can't include
+a generic `where` clause or any same-type (`==`) constraints.
+In addition,
+using the lightweight syntax for very complex constraints
+can be hard to read.
 
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