Sema: apply scoping SuppAssocType scoping rule roots

The generic parameter at the root of a DependentMemberType is
the main thing we care about in terms of the scoping rule.

We have a check for ineffective / invalid inverses in a later
phase, so if the suppression on the type member was wrong then
we should still raise an error about it.

Author: kavon

lib/AST/RequirementMachine/ApplyInverses.cpp

@@ -204,7 +204,8 @@ void swift::rewriting::applyInverses(
     //       func f() where Self: ~Copyable
     //     }
     //
-    if (representativeGPs.find(canSubject) == representativeGPs.end()) {
+    auto subjectRoot = canSubject->getDependentMemberRoot()->getCanonicalType();
+    if (representativeGPs.find(subjectRoot) == representativeGPs.end()) {
       errors.push_back(
           RequirementError::forInvalidInverseOuterSubject(inverse));
       continue;

test/Generics/inverse_assoc_types.swift

@@ -156,10 +156,8 @@ protocol Veggie<A> {
 }
 protocol Carrot: Veggie
   where Self.NeedsCopyable: ~Copyable {} // expected-error {{'Self.NeedsCopyable' required to be 'Copyable' but is marked with '~Copyable'}}
-  // expected-error @-1{{cannot suppress '~Copyable' on generic parameter 'Self.NeedsCopyable' defined in outer scope}}
 
 protocol CarrotCake: Carrot where Self.A: ~Copyable {} // expected-error {{'Self.A' required to be 'Copyable' but is marked with '~Copyable'}}
-// expected-error @-1{{cannot suppress '~Copyable' on generic parameter 'Self.A' defined in outer scope}}
 
 func ex1<Cucumber: ~Copyable, Potato>(_ nc: any Veggie<Cucumber>, c: any Veggie<Potato>) {
   reqC(nc.a()) // expected-error {{global function 'reqC' requires that 'Cucumber' conform to 'Copyable'}}
@@ -171,8 +169,6 @@ protocol Bird {
 }
 
 protocol Eagle: Bird where Self.Song: ~Copyable {}// expected-error {{'Self.Song' required to be 'Copyable' but is marked with '~Copyable'}}
-// expected-error @-1{{cannot suppress '~Copyable' on generic parameter 'Self.Song' defined in outer scope}}
-
 
 protocol Pushable<Element> {
   associatedtype Element: ~Copyable

test/Generics/inverse_extensions.swift

@@ -16,8 +16,7 @@ protocol HasAssoc {
   associatedtype A
 }
 extension HasAssoc where Self.A: ~Copyable {}
-// expected-error@-1 {{cannot suppress '~Copyable' on generic parameter 'Self.A' defined in outer scope}}
-// expected-error@-2 {{'Self.A' required to be 'Copyable' but is marked with '~Copyable'}}
+// expected-error@-1 {{'Self.A' required to be 'Copyable' but is marked with '~Copyable'}}
 
 class Box<T: ~Copyable> {}
 extension Box where T: ~Copyable {}