AST: Fix crash-on-invalid when writing ~ followed by a non-protocol

Also reword some diagnostics. We don't want to talk about 'invert' or
'inverse'.

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -2496,7 +2496,7 @@ ERROR(inferred_opaque_type,none,
 
 // Inverse Constraints
 ERROR(inverse_type_not_invertible,none,
-      "type %0 is not invertible", (Type))
+      "type %0 cannot be suppressed", (Type))
 
 // Extensions
 ERROR(non_nominal_extension,none,
@@ -3168,12 +3168,11 @@ ERROR(requires_not_suitable_archetype,none,
       (Type))
 
 ERROR(requires_not_suitable_inverse_subject,none,
-      "cannot apply inverse '~%1' to type %0 in conformance requirement",
+      "cannot suppress '~%1' on type %0",
       (Type, StringRef))
 
 ERROR(requires_not_suitable_inverse_outer_subject,none,
-      "cannot add inverse constraint '%0: ~%1' "
-      "on generic parameter '%0' defined in outer scope",
+      "cannot suppress '~%1' on generic parameter '%0' defined in outer scope",
       (StringRef, StringRef))
 
 ERROR(invalid_shape_requirement,none,
@@ -7619,7 +7618,7 @@ ERROR(inverse_conflicts_explicit_composition, none,
       "composition cannot contain '~%0' when another member requires '%0'",
       (StringRef))
 ERROR(inverse_extension, none,
-      "cannot apply inverse %0 to extension",
+      "cannot suppress %0 in extension",
       (Type))
 ERROR(copyable_illegal_deinit, none,
       "deinitializer cannot be declared in %kind0 that conforms to 'Copyable'",

lib/AST/NameLookup.cpp

@@ -3060,9 +3060,10 @@ directReferencesForTypeRepr(Evaluator &evaluator,
                                                    inverseRepr->getConstraint(), dc,
                                                    allowUsableFromInline);
     if (innerResult.first.size() == 1) {
-      auto *proto = dyn_cast<ProtocolDecl>(innerResult.first[0]);
-      if (auto ip = proto->getInvertibleProtocolKind()) {
-        result.second.insert(*ip);
+      if (auto *proto = dyn_cast<ProtocolDecl>(innerResult.first[0])) {
+        if (auto ip = proto->getInvertibleProtocolKind()) {
+          result.second.insert(*ip);
+        }
       }
     }
 

test/Generics/inverse_extensions.swift

@@ -15,7 +15,7 @@ protocol HasAssoc {
   associatedtype A
 }
 extension HasAssoc where Self.A: ~Copyable {}
-// expected-error@-1 {{cannot add inverse constraint 'Self.A: ~Copyable' on generic parameter 'Self.A' defined in outer scope}}
+// 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'}}
 
 class Box<T: ~Copyable> {}

test/Generics/inverse_generics.swift

@@ -171,11 +171,11 @@ class NiceTry: ~Copyable, Copyable {} // expected-error {{classes cannot be '~Co
 
 
 struct Extendo: ~Copyable {}
-extension Extendo: Copyable, ~Copyable {} // expected-error {{cannot apply inverse '~Copyable' to extension}}
+extension Extendo: Copyable, ~Copyable {} // expected-error {{cannot suppress '~Copyable' in extension}}
 // expected-error@-1 {{struct 'Extendo' required to be 'Copyable' but is marked with '~Copyable'}}
 
 enum EnumExtendo {}
-extension EnumExtendo: ~Copyable {} // expected-error {{cannot apply inverse '~Copyable' to extension}}
+extension EnumExtendo: ~Copyable {} // expected-error {{cannot suppress '~Copyable' in extension}}
 
 extension NeedsCopyable where Self: ~Copyable {}
 // expected-error@-1 {{'Self' required to be 'Copyable' but is marked with '~Copyable'}}

test/Generics/inverse_scoping.swift

@@ -5,16 +5,16 @@
 protocol NoCopyReq: ~Copyable {}
 
 protocol P {
-  func f() where Self: ~Copyable // expected-error {{cannot add inverse constraint 'Self: ~Copyable' on generic parameter 'Self' defined in outer scope}}
+  func f() where Self: ~Copyable // expected-error {{cannot suppress '~Copyable' on generic parameter 'Self' defined in outer scope}}
 
-  func g<T>(_: T) where Self: ~Copyable // expected-error {{cannot add inverse constraint 'Self: ~Copyable' on generic parameter 'Self' defined in outer scope}}
+  func g<T>(_: T) where Self: ~Copyable // expected-error {{cannot suppress '~Copyable' on generic parameter 'Self' defined in outer scope}}
 
   associatedtype AT where Self: ~Copyable // expected-error {{constraint with subject type of 'Self' is not supported; consider adding requirement to protocol inheritance clause instead}}
 
-  // expected-error@+1 {{cannot add inverse constraint 'Self.Alice: ~Copyable' on generic parameter 'Self.Alice' defined in outer scope}}
+  // expected-error@+1 {{cannot suppress '~Copyable' on generic parameter 'Self.Alice' defined in outer scope}}
   associatedtype Bob where Alice: NoCopyReq & ~Copyable
   associatedtype Alice where Bob: ~Copyable
-  // expected-error@-1 {{cannot add inverse constraint 'Self.Bob: ~Copyable' on generic parameter 'Self.Bob' defined in outer scope}}
+  // expected-error@-1 {{cannot suppress '~Copyable' on generic parameter 'Self.Bob' defined in outer scope}}
 }
 
 protocol U {}
@@ -23,13 +23,13 @@ extension U where Self: ~Copyable {}
 // expected-error@-1 {{'Self' required to be 'Copyable' but is marked with '~Copyable'}}
 
 extension P where Self: ~Copyable {
-  func g() where Self: ~Copyable, // expected-error {{cannot add inverse constraint 'Self: ~Copyable' on generic parameter 'Self' defined in outer scope}}
+  func g() where Self: ~Copyable, // expected-error {{cannot suppress '~Copyable' on generic parameter 'Self' defined in outer scope}}
                                   // FIXME: why no similar 2nd error as Escapable here on Self?
 
-                 Self: ~Escapable {}  // expected-error {{cannot add inverse constraint 'Self: ~Escapable' on generic parameter 'Self' defined in outer scope}}
+                 Self: ~Escapable {}  // expected-error {{cannot suppress '~Escapable' on generic parameter 'Self' defined in outer scope}}
                                       // expected-error@-1 {{'Self' required to be 'Escapable' but is marked with '~Escapable'}}
 
-  typealias Me = Self where Self: ~Copyable // expected-error {{cannot add inverse constraint 'Self: ~Copyable' on generic parameter 'Self' defined in outer scope}}
+  typealias Me = Self where Self: ~Copyable // expected-error {{cannot suppress '~Copyable' on generic parameter 'Self' defined in outer scope}}
 
   typealias MeAndU = Self where Self: U
 }
@@ -39,15 +39,15 @@ struct S<T> {
   // expected-note@+2 3{{add}}
   // expected-error@+1 {{parameter of noncopyable type 'U' must specify ownership}}
   func fn<U>(_ u: U)
-    where T: ~Copyable, // expected-error {{cannot add inverse constraint 'T: ~Copyable' on generic parameter 'T' defined in outer scope}}
+    where T: ~Copyable, // expected-error {{cannot suppress '~Copyable' on generic parameter 'T' defined in outer scope}}
                         // expected-error@-1 {{'T' required to be 'Copyable' but is marked with '~Copyable'}}
           U: ~Copyable
           {}
 
   func onlyCopyable() where T: Copyable {}
 
     func fn<U>(_ u: U)
-      where T: ~Escapable, // expected-error {{cannot add inverse constraint 'T: ~Escapable' on generic parameter 'T' defined in outer scope}}
+      where T: ~Escapable, // expected-error {{cannot suppress '~Escapable' on generic parameter 'T' defined in outer scope}}
                            // expected-error@-1 {{'T' required to be 'Escapable' but is marked with '~Escapable'}}
             U: ~Escapable
             {}
@@ -57,5 +57,5 @@ extension S where T: NoCopyReq & ~Copyable {}
 // expected-error@-1 {{'T' required to be 'Copyable' but is marked with '~Copyable'}}
 
 struct ExtraInverse<T: ~Copyable> {
-  func check() where T: ~Copyable {} // expected-error {{cannot add inverse constraint 'T: ~Copyable' on generic parameter 'T' defined in outer scope}}
+  func check() where T: ~Copyable {} // expected-error {{cannot suppress '~Copyable' on generic parameter 'T' defined in outer scope}}
 }

test/Parse/inverses.swift

@@ -7,18 +7,18 @@ enum Maybe<Thing: ~Copyable> : ~Copyable {}
 func more() {
   let _: any ~Copyable = 19
 
-  let _: any ~Equatable = 19  // expected-error@:14 {{type 'Equatable' is not invertible}}
+  let _: any ~Equatable = 19  // expected-error@:14 {{type 'Equatable' cannot be suppressed}}
 
-  let _: any (~Copyable & ~Equatable) // expected-error{{type 'Equatable' is not invertible}}
+  let _: any (~Copyable & ~Equatable) // expected-error{{type 'Equatable' cannot be suppressed}}
 
-  let _: ~Any // expected-error {{type 'Any' is not invertible}}
-  let _: ~AnyObject // expected-error {{type 'AnyObject' is not invertible}}
+  let _: ~Any // expected-error {{type 'Any' cannot be suppressed}}
+  let _: ~AnyObject // expected-error {{type 'AnyObject' cannot be suppressed}}
 }
 
-struct S4: ~(Copyable & Equatable) {} // expected-error {{type 'Equatable' is not invertible}}
+struct S4: ~(Copyable & Equatable) {} // expected-error {{type 'Equatable' cannot be suppressed}}
 
 func blah<T>(_ t: borrowing T) where T: ~Copyable,
-                                     T: ~Hashable {}  // expected-error@:41 {{type 'Hashable' is not invertible}}
+                                     T: ~Hashable {}  // expected-error@:41 {{type 'Hashable' cannot be suppressed}}
 
 func foo<T: ~Copyable>(x: borrowing T) {}
 
@@ -35,13 +35,13 @@ protocol Foo: ~Copyable
     associatedtype Touch : ~Copyable,
                            ~Copyable
 
-    func test<T>(_ t: T) where T: ~Self  // expected-error {{type 'Self' is not invertible}}
+    func test<T>(_ t: T) where T: ~Self  // expected-error {{type 'Self' cannot be suppressed}}
 }
 
 protocol Sando { func make() }
 
 class C: ~Copyable,  // expected-error {{classes cannot be '~Copyable'}}
-         ~Sando // expected-error {{type 'Sando' is not invertible}}
+         ~Sando // expected-error {{type 'Sando' cannot be suppressed}}
          {}
 
 public struct MoveOnlyS1<T> : ~Copyable { /*deinit {}*/ }
@@ -52,12 +52,12 @@ protocol Rope<Element>: Hashable, ~Copyable {  // expected-error {{'Self' requir
   associatedtype Element: ~Copyable
 }
 
-extension S: ~Copyable {} // expected-error {{cannot apply inverse '~Copyable' to extension}}
+extension S: ~Copyable {} // expected-error {{cannot suppress '~Copyable' in extension}}
 
-struct S: ~U, // expected-error {{type 'U' is not invertible}}
+struct S: ~U, // expected-error {{type 'U' cannot be suppressed}}
           ~Copyable {}
 
-func greenBay<each T: ~Copyable>(_ r: repeat each T) {} // expected-error{{cannot apply inverse '~Copyable' to type 'each T' in conformance requirement}}
+func greenBay<each T: ~Copyable>(_ r: repeat each T) {} // expected-error{{cannot suppress '~Copyable' on type 'each T'}}
 
 typealias Clone = Copyable
 func dup<D: ~Clone>(_ d: D) {}
@@ -73,28 +73,32 @@ func superb(_ thing: some ~Copyable, thing2: some ~Clone) {}
 // expected-note@-2 2{{add 'inout'}}
 // expected-note@-3 2{{add 'consuming'}}
 
-func ownership1(_ t: borrowing any ~Equatable) {} // expected-error {{type 'Equatable' is not invertible}}
+func ownership1(_ t: borrowing any ~Equatable) {} // expected-error {{type 'Equatable' cannot be suppressed}}
 
 func ownership2(_ t: ~ borrowing Int) {} // expected-error {{cannot find type 'borrowing' in scope}}
                                          // expected-error@-1 {{unnamed parameters must be written with the empty name '_'}}
                                          // expected-error@-2 {{expected ',' separator}}
 
 func ownership3(_ t: consuming some ~Clone) {}
 
-func what(one: ~Copyable..., // expected-error {{type 'any Copyable' is not invertible}}
+func what(one: ~Copyable..., // expected-error {{type 'any Copyable' cannot be suppressed}}
           two: ~(Copyable...) // expected-error {{variadic parameter cannot appear outside of a function parameter list}}
-                              // expected-error@-1 {{type 'any Copyable' is not invertible}}
+                              // expected-error@-1 {{type 'any Copyable' cannot be suppressed}}
           ) {}
 
 struct A { struct B { struct C {} } }
 
 typealias Z1 = (~Copyable).Type // FIXME: should be an error
-typealias Z1 = ~Copyable.Type // expected-error {{type 'any Copyable.Type' is not invertible}}
-typealias Z2 = ~A.B.C // expected-error {{type 'A.B.C' is not invertible}}
-typealias Z3 = ~A? // expected-error {{type 'A?' is not invertible}}
-typealias Z4 = ~Rope<Int> // expected-error {{type 'Rope<Int>' is not invertible}}
-typealias Z5 = (~Int) -> Void // expected-error {{type 'Int' is not invertible}}
+typealias Z1 = ~Copyable.Type // expected-error {{type 'any Copyable.Type' cannot be suppressed}}
+typealias Z2 = ~A.B.C // expected-error {{type 'A.B.C' cannot be suppressed}}
+typealias Z3 = ~A? // expected-error {{type 'A?' cannot be suppressed}}
+typealias Z4 = ~Rope<Int> // expected-error {{type 'Rope<Int>' cannot be suppressed}}
+typealias Z5 = (~Int) -> Void // expected-error {{type 'Int' cannot be suppressed}}
 typealias Z6 = ~() -> () // expected-error {{single argument function types require parentheses}}
-                         // expected-error@-1 {{type '()' is not invertible}}
-typealias Z7 = ~(Copyable & Hashable) // expected-error {{type 'Hashable' is not invertible}}
+                         // expected-error@-1 {{type '()' cannot be suppressed}}
+typealias Z7 = ~(Copyable & Hashable) // expected-error {{type 'Hashable' cannot be suppressed}}
 typealias Z8 = ~Copyable & Hashable // expected-error {{composition cannot contain '~Copyable' when another member requires 'Copyable'}}
+
+struct NotAProtocol {}
+
+struct Bad: ~NotAProtocol {} // expected-error {{type 'NotAProtocol' cannot be suppressed}}