[SR-12460] Don't crash when missing a type in a Diagnostic message. (#30979)

* Don't crash when missing a type in a Diagnostic message.
Print an empty string for the missing type.

Resolves SR-12460

* Added new diagnostic message, eg. "operator '==' declared in extension must be 'static'"

Author: blueeor

include/swift/AST/DiagnosticsSema.def

@@ -902,8 +902,8 @@ ERROR(nonstatic_operator_in_nominal,none,
       "operator %0 declared in type %1 must be 'static'",
       (Identifier, DeclName))
 ERROR(nonstatic_operator_in_extension,none,
-      "operator %0 declared in extension of %1 must be 'static'",
-      (Identifier, TypeRepr*))
+      "operator %0 declared in extension%select{| of %2}1 must be 'static'",
+      (Identifier, bool, TypeRepr*))
 ERROR(nonfinal_operator_in_class,none,
       "operator %0 declared in non-final class %1 must be 'final'",
       (Identifier, Type))

lib/AST/DiagnosticEngine.cpp

@@ -583,11 +583,14 @@ static void formatDiagnosticArgument(StringRef Modifier,
     }
     break;
   }
+
   case DiagnosticArgumentKind::TypeRepr:
     assert(Modifier.empty() && "Improper modifier for TypeRepr argument");
+    assert(Arg.getAsTypeRepr() && "TypeRepr argument is null");
     Out << FormatOpts.OpeningQuotationMark << Arg.getAsTypeRepr()
         << FormatOpts.ClosingQuotationMark;
     break;
+
   case DiagnosticArgumentKind::PatternKind:
     assert(Modifier.empty() && "Improper modifier for PatternKind argument");
     Out << Arg.getAsPatternKind();

lib/Sema/TypeCheckDecl.cpp

@@ -676,8 +676,9 @@ IsStaticRequest::evaluate(Evaluator &evaluator, FuncDecl *decl) const {
       dc->isTypeContext()) {
     const auto operatorName = decl->getBaseIdentifier();
     if (auto ED = dyn_cast<ExtensionDecl>(dc->getAsDecl())) {
-      decl->diagnose(diag::nonstatic_operator_in_extension,
-                     operatorName, ED->getExtendedTypeRepr())
+      decl->diagnose(diag::nonstatic_operator_in_extension, operatorName,
+                     ED->getExtendedTypeRepr() != nullptr,
+                     ED->getExtendedTypeRepr())
           .fixItInsert(decl->getAttributeInsertionLoc(/*forModifier=*/true),
                        "static ");
     } else {

test/decl/ext/sr_12460.swift

@@ -0,0 +1,9 @@
+// RUN: %target-swift-ide-test -print-indexed-symbols -source-filename %s 2>&1 | %FileCheck -check-prefix CHECK %s
+
+// Test that we don't crash when validating members inside an extension with no type name.
+
+// CHECK: :[[@LINE+1]]:11: error: expected type name in extension declaration
+extension {
+  // CHECK: :[[@LINE+1]]:8: error: operator '==' declared in extension must be 'static'
+  func ==(lhs: Any, rhs: Any) -> Bool {}
+}