Provided FixIts for 'override func' that should be 'override var' and vice-versa

Fixes Issue #57499

Author: Rajveer100

include/swift/AST/DiagnosticsSema.def

@@ -2924,8 +2924,14 @@ ERROR(override_of_non_open,none,
 
 ERROR(method_does_not_override,none,
       "method does not override any method from its %select{parent protocol|superclass}0", (bool))
+NOTE(override_method_in_lieu_of_property,none,
+      "did you mean to override the property %0?", (Identifier))
+
 ERROR(property_does_not_override,none,
       "property does not override any property from its %select{parent protocol|superclass}0", (bool))
+NOTE(override_property_in_lieu_of_method,none,
+      "did you mean to override the method %0?", (Identifier))
+
 ERROR(subscript_does_not_override,none,
       "subscript does not override any subscript from its %select{parent protocol|superclass}0", (bool))
 ERROR(initializer_does_not_override,none,

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -2130,6 +2130,27 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
           } else {
             VD->diagnose(diag::property_does_not_override, isClassContext)
                 .highlight(OA->getLocation());
+            //If the override is a property-decl, check if there exists
+            //a no-args func-decl in the base class, if yes, provide a fix-it.
+            auto declName = VD->getBaseName();
+            auto declType = VD->getResultTypeRepr();
+            auto inherited = DC->getSelfClassDecl()->getInherited();
+            //If there is an inherited context, perform member lookup.
+            if (!inherited.empty()) {
+              auto superClass = inherited.front().getType();
+              auto lookupResult = superClass->getAnyNominal()->lookupDirect(declName);
+              
+              for (auto& candidate : lookupResult) {
+                //If the parameter list is empty, compare the return types
+                //of the candidates with the declaration type.
+                if (getParameterList(candidate)->size() == 0) {
+                  auto candidateReturnType = candidate->getResultTypeRepr();
+                  if (candidateReturnType->getKind() == declType->getKind())
+                    VD->diagnose(diag::override_property_in_lieu_of_method, declName.getIdentifier())
+                        .fixItReplace(VD->Decl::getSourceRangeIncludingAttrs(), "override func " + declName.getIdentifier().str().str() + "() -> " + VD->getInterfaceType()->getRValueType().getString() + " { <#code#> }");
+                }
+              }
+            }
           }
           OA->setInvalid();
         }
@@ -3158,6 +3179,27 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
           } else {
             FD->diagnose(diag::method_does_not_override, isClassContext)
                 .highlight(OA->getLocation());
+            //If the override is a no-args fun-decl, check if there exists
+            //a no-args var-decl in the base class, if yes, provide a fix-it.
+            if (FD->getParameters()->size() == 0) {
+              auto declName = FD->getBaseName();
+              auto declReturnType = FD->getResultInterfaceType()->getRValueType();
+              auto inherited = DC->getSelfClassDecl()->getInherited();
+              //If there is an inherited context, perform member lookup.
+              if (!inherited.empty()) {
+                auto superClass = inherited.front().getType();
+                auto lookupResult = superClass->getAnyNominal()->lookupDirect(declName);
+                //Compare the equality of return types for each candidate.
+                for (auto& candidate : lookupResult) {
+                  auto candidateType = candidate->getInterfaceType()->getRValueType();
+                  if (candidateType->isEqual(declReturnType))
+                    FD->diagnose(diag::override_method_in_lieu_of_property, declName.getIdentifier())
+                        .fixItRemove(FD->getBodySourceRange())
+                        .fixItReplace(FD->getSourceRangeIncludingAttrs(),
+                                      "override var " + declName.getIdentifier().str().str() + ": " + declReturnType.getString() + " { <#code#> }");
+                }
+              }
+            }
           }
           OA->setInvalid();
         }

test/decl/class/override.swift

@@ -414,3 +414,28 @@ open class OpenDerivedFinal : OpenBase {
 open class OpenDerivedStatic : OpenBase {
   override public static func classMethod() {}
 }
+
+// Context: https://github.com/apple/swift/issues/57499
+// FixIt for 'override func' that should be 'override var' and vice-versa
+func overrideInLieu() {
+  
+  class BaseClass {
+    var someValueX: Bool {
+      get { return false }
+      set { }
+    }
+    
+    func someFuncX() -> Int { return 0 }
+  }
+
+  class Inherited: BaseClass {
+    override var someFuncX: Int { // expected-error {{property does not override any property from its superclass}}
+    // expected-note@-1 {{did you mean to override the method 'someFuncX'?}}
+      get { return 0 }
+      set { }
+    }
+    
+    override func someValueX() -> Bool { return false } // expected-error {{method does not override any method from its superclass}}
+    // expected-note@-1 {{did you mean to override the property 'someValueX'?}}
+  }
+}

test/decl/inherit/override.swift

@@ -86,3 +86,28 @@ class ObjCSub : ObjCSuper {
 
   @objc(method3:withInt:) func method3(_ x: Sub, with y: Int) { } // expected-error{{method3(_:with:)' with Objective-C selector 'method3:withInt:' conflicts with method 'method3(_:withInt:)' from superclass 'ObjCSuper' with the same Objective-C selector}}
 }
+
+// Context: https://github.com/apple/swift/issues/57499
+// FixIt for 'override func' that should be 'override var' and vice-versa
+func overrideInLieu() {
+  
+  class BaseClass {
+    var someValueX: Bool {
+      get { return false }
+      set { }
+    }
+    
+    func someFuncX() -> Int { return 0 }
+  }
+
+  class Inherited: BaseClass {
+    override var someFuncX: Int { // expected-error {{property does not override any property from its superclass}}
+    // expected-note@-1 {{did you mean to override the method 'someFuncX'?}}
+      get { return 0 }
+      set { }
+    }
+    
+    override func someValueX() -> Bool { return false } // expected-error {{method does not override any method from its superclass}}
+    // expected-note@-1 {{did you mean to override the property 'someValueX'?}}
+  }
+}