Expand the outline in the guide

Author: amartini51

TSPL.docc/LanguageGuide/OpaqueTypes.md

@@ -924,30 +924,43 @@ which means that the type of `twelve` is also inferred to be `Int`.
 
 ## Opaque Parameter Types
 
-XXX Outline:
-
-- You can write `some` as the type for a parameter
-  to a function, initializer, or subscript.
-- In that usage, it's syntactic sugar for a generic.
-- You can't refer to the generic type -- because it has no name.
-- If you write `some P` more than once,
-  they each refer to a different type.
+In addition to writing `some` to return an opaque type,
+you can also write `some` in the type for a parameter.
+However, when you write `some` in a parameter type
+that's just a shorter syntax for generics, not an opaque type.
+For example,
+both of the functions below are equivalent:
 
 ```swift
-func drawTwice(_ shape: some Shape) -> String {
+func drawTwiceSome(_ shape: some Shape) -> String {
     let drawn = shape.draw()
     return drawn + "\n" + drawn
 }
+
+func drawTwiceGeneric<SomeShape: Shape>(_ shape: SomeShape) -> String { ... }
+```
+
+The `drawTwiceSome(_:)` function
+uses the type `some Shape` for its argument.
+This creates a new, unnamed, generic type parameter for the function
+with a constraint that requires the type to conform to the `Shape` protocol.
+Because the generic type doesn't have a name,
+you can't refer to that type elsewhere in the function.
+The `drawTwiceGeneric(_:)` function
+uses a generic type parameter named `SomeShape`,
+and explicitly includes the protocol conformance requirement.
+
+XXX Every parameter's type is independent
+
+```swift
 func combine(shape s1: some Shape, with s2: some Shape) -> String {
     return s1.draw() + "\n" + s2.draw()
 }
-
-// The same as:
-func drawTwice<SomeShape: Shape>(_ shape: SomeShape) -> String { ... }
 func combine<S1: Shape, S2: Shape>(shape s1: S1, with s2: S2) -> String { ... }
 ```
 
-
+If you need to multiple generic parameters that are all the same type,
+use the usual generic syntax instead.
 
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