[Diagnostics] Split "only concrete types conform to protocols" into a separate note

include/swift/AST/DiagnosticsSema.def

@@ -1842,9 +1842,11 @@ ERROR(use_of_equal_instead_of_equality,none,
       "use of '=' in a boolean context, did you mean '=='?", ())
 ERROR(type_cannot_conform, none,
       "%select{type %1|protocol %1 as a type}0 cannot conform to "
-      "%select{%3|the protocol itself}2; "
-      "only concrete types such as structs, enums and classes can conform to protocols",
+      "%select{%3|the protocol itself}2",
       (bool, Type, bool, Type))
+NOTE(only_concrete_types_conform_to_protocols,none,
+     "only concrete types such as structs, enums and classes can conform to protocols",
+     ())
 NOTE(required_by_opaque_return,none,
     "required by opaque return type of %0 %1", (DescriptiveDeclKind, DeclName))
 NOTE(required_by_decl,none,

lib/Sema/CSDiagnostics.cpp

@@ -516,6 +516,8 @@ bool MissingConformanceFailure::diagnoseTypeCannotConform(
                  nonConformingType->isEqual(protocolType),
                  protocolType);
 
+  emitDiagnostic(diag::only_concrete_types_conform_to_protocols);
+
   if (auto *OTD = dyn_cast<OpaqueTypeDecl>(AffectedDecl)) {
     auto *namingDecl = OTD->getNamingDecl();
     if (auto *repr = namingDecl->getOpaqueResultTypeRepr()) {
@@ -2171,6 +2173,7 @@ bool ContextualFailure::diagnoseAsError() {
         emitDiagnostic(diag::type_cannot_conform,
                        /*isExistentialType=*/true, fromType, 
                        fromType->isEqual(toType), toType);
+        emitDiagnostic(diag::only_concrete_types_conform_to_protocols);
         return true;
       }
 

lib/Sema/TypeCheckProtocol.cpp

@@ -4735,6 +4735,8 @@ void swift::diagnoseConformanceFailure(Type T,
       diags.diagnose(ComplainLoc, diag::type_cannot_conform, true,
                      T, T->isEqual(Proto->getDeclaredInterfaceType()), 
                      Proto->getDeclaredInterfaceType());
+      diags.diagnose(ComplainLoc,
+                     diag::only_concrete_types_conform_to_protocols);
       return;
     }
 

test/Constraints/diagnostics.swift

@@ -51,9 +51,9 @@ f0(i, i, // expected-error@:7 {{cannot convert value of type 'Int' to expected a
 
 
 // Cannot conform to protocols.
-f5(f4)  // expected-error {{type '(Int) -> Int' cannot conform to 'P2'; only concrete types such as structs, enums and classes can conform to protocols}}
-f5((1, "hello"))  // expected-error {{type '(Int, String)' cannot conform to 'P2'; only concrete types such as structs, enums and classes can conform to protocols}}
-f5(Int.self) // expected-error {{type 'Int.Type' cannot conform to 'P2'; only concrete types such as structs, enums and classes can conform to protocols}}
+f5(f4)  // expected-error {{type '(Int) -> Int' cannot conform to 'P2'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
+f5((1, "hello"))  // expected-error {{type '(Int, String)' cannot conform to 'P2'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
+f5(Int.self) // expected-error {{type 'Int.Type' cannot conform to 'P2'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 
 // Tuple element not convertible.
 f0(i,
@@ -104,7 +104,7 @@ func f8<T:P2>(_ n: T, _ f: @escaping (T) -> T) {}  // expected-note {{where 'T'
 f8(3, f4) // expected-error {{global function 'f8' requires that 'Int' conform to 'P2'}}
 typealias Tup = (Int, Double)
 func f9(_ x: Tup) -> Tup { return x }
-f8((1,2.0), f9) // expected-error {{type 'Tup' (aka '(Int, Double)') cannot conform to 'P2'; only concrete types such as structs, enums and classes can conform to protocols}}
+f8((1,2.0), f9) // expected-error {{type 'Tup' (aka '(Int, Double)') cannot conform to 'P2'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 
 // <rdar://problem/19658691> QoI: Incorrect diagnostic for calling nonexistent members on literals
 1.doesntExist(0)  // expected-error {{value of type 'Int' has no member 'doesntExist'}}

test/Constraints/generics.swift

@@ -188,7 +188,7 @@ func r22459135() {
 
 // <rdar://problem/19710848> QoI: Friendlier error message for "[] as Set"
 // <rdar://problem/22326930> QoI: "argument for generic parameter 'Element' could not be inferred" lacks context
-_ = [] as Set  // expected-error {{protocol 'Any' as a type cannot conform to 'Hashable'; only concrete types such as structs, enums and classes can conform to protocols}}
+_ = [] as Set  // expected-error {{protocol 'Any' as a type cannot conform to 'Hashable'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 // expected-note@-1 {{required by generic struct 'Set' where 'Element' = 'Any'}}
 
 

test/Constraints/rdar68155466.swift

@@ -25,4 +25,4 @@ func data() -> [A] {
 }
 
 _ = Loop(data(), id: \.uniqueID) { $0 } // expected-error {{key path cannot refer to instance method 'uniqueID()'}}
-// expected-error@-1 {{type '() -> Int' cannot conform to 'Hashable'; only concrete types such as structs, enums and classes can conform to protocols}}
+// expected-error@-1 {{type '() -> Int' cannot conform to 'Hashable'}} expected-note@-1 {{only concrete types such as structs, enums and classes can conform to protocols}}

test/Constraints/result_builder_diags.swift

@@ -195,7 +195,7 @@ struct Label<L> : P where L : P { // expected-note 2 {{'L' declared as parameter
 }
 
 func test_51167632() -> some P {
-  AnyP(G { // expected-error {{type 'Label<_>.Type' cannot conform to 'P'; only concrete types such as structs, enums and classes can conform to protocols}}
+  AnyP(G { // expected-error {{type 'Label<_>.Type' cannot conform to 'P'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
     Text("hello")
     Label  // expected-error {{generic parameter 'L' could not be inferred}}
     // expected-note@-1 {{explicitly specify the generic arguments to fix this issue}} {{10-10=<<#L: P#>>}}

test/Generics/conditional_conformances_literals.swift

@@ -128,9 +128,9 @@ func combined() {
 
     // Needs self conforming protocols:
     let _: Conforms = [[0: [1 : [works]] as Conforms]]
-    // expected-error@-1 {{protocol 'Conforms' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+    // expected-error@-1 {{protocol 'Conforms' as a type cannot conform to the protocol itself}} expected-note@-1 {{only concrete types such as structs, enums and classes can conform to protocols}}
 
     let _: Conforms = [[0: [1 : [fails]] as Conforms]]
     // expected-error@-1 {{protocol 'Conforms' requires that 'Fails' conform to 'Conforms'}}
-    // expected-error@-2 {{protocol 'Conforms' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+    // expected-error@-2 {{protocol 'Conforms' as a type cannot conform to the protocol itself}} expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
 }

test/Generics/existential_restrictions.swift

@@ -23,7 +23,7 @@ func fAOE(_ t: AnyObject) { }
 func fT<T>(_ t: T) { }
 
 func testPassExistential(_ p: P, op: OP, opp: OP & P, cp: CP, sp: SP, any: Any, ao: AnyObject) {
-  fP(p) // expected-error{{protocol 'P' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+  fP(p) // expected-error{{protocol 'P' as a type cannot conform to the protocol itself}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
   fAO(p) // expected-error{{global function 'fAO' requires that 'P' be a class type}}
   fAOE(p) // expected-error{{argument type 'P' expected to be an instance of a class or class-constrained type}}
   fT(p)
@@ -37,8 +37,8 @@ func testPassExistential(_ p: P, op: OP, opp: OP & P, cp: CP, sp: SP, any: Any,
   fAOE(cp)
   fT(cp)
 
-  fP(opp) // expected-error{{protocol 'OP & P' as a type cannot conform to 'P'; only concrete types such as structs, enums and classes can conform to protocols}}
-  fOP(opp) // expected-error{{protocol 'OP & P' as a type cannot conform to 'OP'; only concrete types such as structs, enums and classes can conform to protocols}}
+  fP(opp) // expected-error{{protocol 'OP & P' as a type cannot conform to 'P'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
+  fOP(opp) // expected-error{{protocol 'OP & P' as a type cannot conform to 'OP'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
   fAO(opp) // expected-error{{global function 'fAO' requires that 'OP & P' be a class type}}
   fAOE(opp)
   fT(opp)
@@ -64,9 +64,9 @@ class GAO<T : AnyObject> {} // expected-note 2{{requirement specified as 'T' : '
 func blackHole(_ t: Any) {}
 
 func testBindExistential() {
-  blackHole(GP<P>()) // expected-error{{protocol 'P' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+  blackHole(GP<P>()) // expected-error{{protocol 'P' as a type cannot conform to the protocol itself}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
   blackHole(GOP<OP>())
-  blackHole(GCP<CP>()) // expected-error{{protocol 'CP' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+  blackHole(GCP<CP>()) // expected-error{{protocol 'CP' as a type cannot conform to the protocol itself}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
   blackHole(GAO<P>()) // expected-error{{'GAO' requires that 'P' be a class type}}
   blackHole(GAO<OP>())
   blackHole(GAO<CP>()) // expected-error{{'GAO' requires that 'CP' be a class type}}
@@ -92,5 +92,5 @@ func foo() {
   // generic no overloads error path. The error should actually talk
   // about the return type, and this can happen in other contexts as well;
   // <rdar://problem/21900971> tracks improving QoI here.
-  allMine.takeAll() // expected-error{{protocol 'Mine' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+  allMine.takeAll() // expected-error{{protocol 'Mine' as a type cannot conform to the protocol itself}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 }

test/Parse/confusables.swift

@@ -17,9 +17,10 @@ if (true ꝸꝸꝸ false) {} // expected-note {{identifier 'ꝸꝸꝸ' contains
 
 // expected-error @+3 {{invalid character in source file}}
 // expected-error @+2 {{expected ',' separator}}
-// expected-error @+1 {{type '(Int, Int)' cannot conform to 'BinaryInteger'; only concrete types such as structs, enums and classes can conform to protocols}}
+// expected-error @+1 {{type '(Int, Int)' cannot conform to 'BinaryInteger'}}
 if (5 ‒ 5) == 0 {} // expected-note {{unicode character '‒' (Figure Dash) looks similar to '-' (Hyphen Minus); did you mean to use '-' (Hyphen Minus)?}} {{7-10=-}}
 // expected-note @-1 {{operator function '=='}}
+// expected-note @-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
 
 // FIXME(rdar://61028087): The above note should read "required by referencing operator function '==' on 'BinaryInteger' where 'Self' = '(Int, Int)'".
 

test/decl/protocol/conforms/error_self_conformance.swift

@@ -11,15 +11,15 @@ func testSimple(error: Error) {
 
 protocol ErrorRefinement : Error {}
 func testErrorRefinment(error: ErrorRefinement) {
-  wantsError(error) // expected-error {{protocol 'ErrorRefinement' as a type cannot conform to 'Error'; only concrete types such as structs, enums and classes can conform to protocols}}
+  wantsError(error) // expected-error {{protocol 'ErrorRefinement' as a type cannot conform to 'Error'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 }
 
 protocol OtherProtocol {}
 func testErrorComposition(error: Error & OtherProtocol) {
-  wantsError(error) // expected-error {{protocol 'Error & OtherProtocol' as a type cannot conform to 'Error'; only concrete types such as structs, enums and classes can conform to protocols}}
+  wantsError(error) // expected-error {{protocol 'Error & OtherProtocol' as a type cannot conform to 'Error'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 }
 
 class C {}
 func testErrorCompositionWithClass(error: Error & C) {
-  wantsError(error) // expected-error {{protocol 'C & Error' as a type cannot conform to 'Error'; only concrete types such as structs, enums and classes can conform to protocols}}
+  wantsError(error) // expected-error {{protocol 'C & Error' as a type cannot conform to 'Error'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
 }

test/stmt/foreach.swift

@@ -177,7 +177,7 @@ func testOptionalSequence() {
 
 // Crash with (invalid) for each over an existential
 func testExistentialSequence(s: Sequence) { // expected-error {{protocol 'Sequence' can only be used as a generic constraint because it has Self or associated type requirements}}
-  for x in s { // expected-error {{protocol 'Sequence' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+  for x in s { // expected-error {{protocol 'Sequence' as a type cannot conform to the protocol itself}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
     _ = x
   }
 }

test/type/opaque.swift

@@ -383,7 +383,7 @@ protocol P_51641323 {
 func rdar_51641323() {
   struct Foo: P_51641323 {
     var foo: some P_51641323 { // expected-note {{required by opaque return type of property 'foo'}}
-      {} // expected-error {{type '() -> ()' cannot conform to 'P_51641323'; only concrete types such as structs, enums and classes can conform to protocols}}
+      {} // expected-error {{type '() -> ()' cannot conform to 'P_51641323'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
     }
   }
 }

test/type/subclass_composition.swift

@@ -413,7 +413,8 @@ func conformsTo<T1 : P2, T2 : Base<Int> & P2>(
   // expected-error@-1 {{global function 'conformsToAnyObject' requires that 'P1' be a class type}}
 
   conformsToP1(p1)
-  // expected-error@-1 {{protocol 'P1' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+  // expected-error@-1 {{protocol 'P1' as a type cannot conform to the protocol itself}}
+  // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
 
   // FIXME: Following diagnostics are not great because when
   // `conformsTo*` methods are re-typechecked, they loose information

validation-test/compiler_crashers_2_fixed/0196-rdar48937223.swift

@@ -6,7 +6,7 @@ func fn<T, U: P>(_ arg1: T, arg2: (T) -> U) {}
 // expected-note@-1 {{required by global function 'fn(_:arg2:)' where 'U' = '()'}}
 
 func test(str: String) {
-  fn(str) { arg in // expected-error {{type '()' cannot conform to 'P'; only concrete types such as structs, enums and classes can conform to protocols}}
+  fn(str) { arg in // expected-error {{type '()' cannot conform to 'P'}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}
     <#FOO#> // expected-error {{editor placeholder in source file}}
   }
 }

validation-test/compiler_crashers_fixed/00017-llvm-foldingset-llvm-attributesetnode-nodeequals.swift

@@ -20,4 +20,4 @@ extension Bool : BooleanProtocol {
 func f<T : BooleanProtocol>(_ b: T) {}
 // expected-note@-1 {{required by global function 'f' where 'T' = 'BooleanProtocol'}}
 
-f(true as BooleanProtocol) // expected-error {{protocol 'BooleanProtocol' as a type cannot conform to the protocol itself; only concrete types such as structs, enums and classes can conform to protocols}}
+f(true as BooleanProtocol) // expected-error {{protocol 'BooleanProtocol' as a type cannot conform to the protocol itself}} expected-note {{only concrete types such as structs, enums and classes can conform to protocols}}