update diagnostics

Author: OnyekachiSamuel

include/swift/AST/DiagnosticsSema.def

@@ -1801,11 +1801,11 @@ ERROR(type_cannot_conform_to_nsobject,none,
 
 ERROR(use_of_equal_instead_of_equality,none,
       "use of '=' in a boolean context, did you mean '=='?", ())
-
 ERROR(type_cannot_conform, none,
-      "%select{|A value of protocol }0type %1 does not conform to the protocol itself (exception: 'Error'); "
+      "%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",
-      (bool, Type, Type))
+      (bool, Type, bool, Type))
 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

@@ -474,7 +474,7 @@ bool MissingConformanceFailure::diagnoseTypeCannotConform(
   }
 
   emitDiagnostic(diag::type_cannot_conform,
-                 nonConformingType->isExistentialType(), nonConformingType,
+                 nonConformingType->isExistentialType(), nonConformingType, nonConformingType->isEqual(protocolType),
                  protocolType);
 
   if (auto *OTD = dyn_cast<OpaqueTypeDecl>(AffectedDecl)) {
@@ -2061,7 +2061,7 @@ bool ContextualFailure::diagnoseAsError() {
     if (CTP == CTP_ForEachStmt) {
       if (fromType->isAnyExistentialType()) {
         emitDiagnostic(diag::type_cannot_conform,
-                       /*isExistentialType=*/true, fromType, toType);
+                       /*isExistentialType=*/true, fromType, fromType->isEqual(toType), toType);
         return true;
       }
 

lib/Sema/TypeCheckProtocol.cpp

@@ -4256,7 +4256,7 @@ void swift::diagnoseConformanceFailure(Type T,
 
     if (!T->isObjCExistentialType()) {
       diags.diagnose(ComplainLoc, diag::type_cannot_conform, true,
-                     T, Proto->getDeclaredType());
+                     T, T->isEqual(Proto->getDeclaredType()), Proto->getDeclaredType());
       return;
     }