Merge pull request #59967 from CodaFi/prime-cuts

Improve Diagnostics for Over-Constrained Protocol Types

Author: swift-ci

include/swift/AST/DiagnosticsSema.def

@@ -3762,7 +3762,8 @@ ERROR(protocol_declares_unknown_primary_assoc_type,none,
 ERROR(protocol_declares_duplicate_primary_assoc_type,none,
       "duplicate primary associated type name %0", (Identifier))
 ERROR(protocol_does_not_have_primary_assoc_type,none,
-      "cannot specialize protocol type %0", (Type))
+      "protocol %0 does not have primary associated types that can be "
+      "constrained", (Type))
 ERROR(parameterized_protocol_type_argument_count_mismatch,none,
       "protocol type %0 specialized with %select{too many|too few}3 type arguments "
       "(got %1, but expected %2)",

lib/Sema/TypeCheckType.cpp

@@ -621,8 +621,12 @@ static Type applyGenericArguments(Type type, TypeResolution resolution,
     auto assocTypes = protoDecl->getPrimaryAssociatedTypes();
     if (assocTypes.empty()) {
       diags.diagnose(loc, diag::protocol_does_not_have_primary_assoc_type,
-                     protoType);
-
+                     protoType)
+           .fixItRemove(generic->getAngleBrackets());
+      if (!protoDecl->isImplicit()) {
+        diags.diagnose(protoDecl, diag::decl_declared_here,
+                       protoDecl->getName());
+      }
       return ErrorType::get(ctx);
     }
 

test/Generics/generic_types.swift

@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift
 
-protocol MyFormattedPrintable {
+protocol MyFormattedPrintable { // expected-note 3 {{declared here}}
   func myFormat() -> String
 }
 
@@ -258,3 +258,10 @@ extension X8 where T == MetatypeTypeResolutionProto {
   static var property2: T.Type { property1 } // ok, still .Protocol
   static func method2() -> T.Type { method1() } // ok, still .Protocol
 }
+
+func bogusProtocolConstraint1(_ : any MyFormattedPrintable<String>) {}
+// expected-error@-1 {{protocol 'MyFormattedPrintable' does not have primary associated types that can be constrained}}{{59-67=}}
+func bogusProtocolConstraint2(_ : some MyFormattedPrintable<String>) {}
+// expected-error@-1 {{protocol 'MyFormattedPrintable' does not have primary associated types that can be constrained}}{{60-68=}}
+func bogusProtocolConstraint3(_ : MyFormattedPrintable<String>) {}
+// expected-error@-1 {{protocol 'MyFormattedPrintable' does not have primary associated types that can be constrained}}{{55-63=}}