Make diagnoseSelfAssignment a utility

Author: CodaFi

lib/Sema/CSDiagnostics.cpp

@@ -1333,10 +1333,9 @@ bool RValueTreatedAsLValueFailure::diagnoseAsError() {
     return false;
 
   if (auto assignExpr = dyn_cast<AssignExpr>(diagExpr)) {
-    auto &TC = getTypeChecker();
     // Let's check whether this is an attempt to assign
     // variable or property to itself.
-    if (TC.diagnoseSelfAssignment(assignExpr))
+    if (TypeChecker::diagnoseSelfAssignment(assignExpr))
       return true;
 
     diagExpr = assignExpr->getDest();

lib/Sema/CSFix.cpp

@@ -885,11 +885,10 @@ bool IgnoreAssignmentDestinationType::diagnose(Expr *root, bool asNote) const {
   // `let _ = { $0 = $0 = 42 }`. Assignment chaining results in
   // type mismatch between result of the previous assignment and the next.
   {
-    auto &TC = cs.getTypeChecker();
     llvm::SaveAndRestore<AssignExpr *> anchor(AE);
 
     do {
-      if (TC.diagnoseSelfAssignment(AE))
+      if (TypeChecker::diagnoseSelfAssignment(AE))
         return true;
     } while ((AE = dyn_cast_or_null<AssignExpr>(cs.getParentExpr(AE))));
   }

lib/Sema/MiscDiagnostics.cpp

@@ -3983,7 +3983,7 @@ static void diagnoseDeprecatedWritableKeyPath(TypeChecker &TC, const Expr *E,
 void swift::performSyntacticExprDiagnostics(TypeChecker &TC, const Expr *E,
                                             const DeclContext *DC,
                                             bool isExprStmt) {
-  TC.diagnoseSelfAssignment(E);
+  TypeChecker::diagnoseSelfAssignment(E);
   diagSyntacticUseRestrictions(TC, E, DC, isExprStmt);
   diagRecursivePropertyAccess(TC, E, DC);
   diagnoseImplicitSelfUseInClosure(TC, E, DC);

lib/Sema/TypeChecker.h

@@ -1842,7 +1842,7 @@ class TypeChecker final {
   }
 
   /// Diagnose assigning variable to itself.
-  bool diagnoseSelfAssignment(const Expr *E);
+  static bool diagnoseSelfAssignment(const Expr *E);
 
   /// Builds a string representing a "default" generic argument list for
   /// \p typeDecl. In general, this means taking the bound of each generic