[Embedded] Downgrade type-checker error about non-final generic class methods to a warning

The existing SIL-level diagnostic for this check only triggers when
the type is actually used, while the type-checker version is more
eager. Stage in the stricter check as a warning and we'll clamp down
on things later.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -8612,9 +8612,10 @@ GROUPED_ERROR(weak_unowned_in_embedded_swift, EmbeddedRestrictions, none,
 GROUPED_WARNING(untyped_throws_in_embedded_swift, EmbeddedRestrictions,
                 DefaultIgnore,
                 "untyped throws is not available in Embedded Swift; add a thrown error type with '(type)'", ())
-GROUPED_ERROR(generic_nonfinal_in_embedded_swift, EmbeddedRestrictions, none,
-              "generic %kind0 in a class %select{must be 'final'|cannot be 'required'}1 in Embedded Swift",
-              (const Decl *, bool))
+GROUPED_WARNING(generic_nonfinal_in_embedded_swift, EmbeddedRestrictions,
+                DefaultIgnore,
+                "generic %kind0 in a class %select{must be 'final'|cannot be 'required'}1 in Embedded Swift",
+                (const Decl *, bool))
 GROUPED_WARNING(use_generic_member_of_existential_in_embedded_swift,
                 EmbeddedRestrictions, DefaultIgnore,
                 "cannot use generic %kind0 on a value of type %1 in Embedded Swift",

test/embedded/classes-non-final-method-no-stdlib.swift

@@ -4,7 +4,8 @@
 // REQUIRES: swift_feature_Embedded
 
 public class MyClass {
-  public func foo<T>(t: T) { } // expected-error {{generic instance method 'foo(t:)' in a class must be 'final' in Embedded Swift}}
+  public func foo<T>(t: T) { } // expected-warning {{generic instance method 'foo(t:)' in a class must be 'final' in Embedded Swift}}
+  // expected-error@-1{{classes cannot have a non-final, generic method 'foo(t:)' in embedded Swift}}
   public func bar() { }
 }
 
@@ -24,7 +25,8 @@ func testit2() -> C2<S> {
 }
 
 open class C3<X> {
-  public func foo<T>(t: T) {} // expected-error {{generic instance method 'foo(t:)' in a class must be 'final' in Embedded Swift}}
+  public func foo<T>(t: T) {} // expected-warning {{generic instance method 'foo(t:)' in a class must be 'final' in Embedded Swift}}
+  // expected-error@-1{{classes cannot have a non-final, generic method 'foo(t:)' in embedded Swift}}
 }
 
 func testit3() -> C3<S> {

test/embedded/restrictions.swift

@@ -71,18 +71,15 @@ public struct MyStruct {
 protocol P { }
 
 class MyGenericClass<T> {
-  func f<U>(value: U) { } // expected-nonembedded-warning{{generic instance method 'f(value:)' in a class must be 'final' in Embedded Swift}}
-  // expected-embedded-error@-1{{generic instance method 'f(value:)' in a class must be 'final' in Embedded Swift}}
+  func f<U>(value: U) { } // expected-warning{{generic instance method 'f(value:)' in a class must be 'final' in Embedded Swift}}
   func g() { }
-  class func h() where T: P { } // expected-nonembedded-warning{{generic class method 'h()' in a class must be 'final' in Embedded Swift}}
-  // expected-embedded-error@-1{{generic class method 'h()' in a class must be 'final' in Embedded Swift}}
+  class func h() where T: P { } // expected-warning{{generic class method 'h()' in a class must be 'final' in Embedded Swift}}
 
   init<U>(value: U) { } // okay, can be directly called
 
   required init() { } // non-generic is okay
 
-  required init<V>(something: V) { } // expected-nonembedded-warning{{generic initializer 'init(something:)' in a class cannot be 'required' in Embedded Swift}}
-  // expected-embedded-error@-1{{generic initializer 'init(something:)' in a class cannot be 'required' in Embedded Swift}}
+  required init<V>(something: V) { } // expected-warning{{generic initializer 'init(something:)' in a class cannot be 'required' in Embedded Swift}}
 }
 
 // ---------------------------------------------------------------------------