support @equalsAndHashCode (#70)

* equalsAndHashCode
* support custom canEqual

README.md

@@ -43,6 +43,7 @@
 - `@log`
 - `@apply`
 - `@constructor`
+- `@equalsAndHashCode`
 
 > 涉及到交互操作的注解在IDEA插件中都得到了支持。在插件市场中搜索`Scala-Macro-Tools`可下载。
 

README_EN.md

@@ -27,6 +27,7 @@ Learn Scala macro and abstract syntax tree.
 - `@log`
 - `@apply`
 - `@constructor`
+- `@equalsAndHashCode`
 
 > Annotations involving interaction are supported in the idea plug-in (named `Scala-Macro-Tools` in Marketplace).
 

docs/howToUse.md

@@ -213,4 +213,44 @@ def <init>(int: Int, j: Int, k: Option[String], t: Option[Long], b: Int) = {
   <init>(int, j, k, t);
   this.b = b
 }
-```
\ No newline at end of file
+```
+
+## @equalsAndHashCode
+
+`@equalsAndHashCode`注解用于为普通类生成`equals`和`hashCode`方法，同时均考虑超类的影响。
+
+- 说明
+  - `verbose` 指定是否开启详细编译日志。可选，默认`false`。
+  - `excludeFields` 指定是否需要排除不需要用于`equals`和`hashCode`方法的字段。可选，默认空（class内部所有非私有的`var、val`字段都将被应用于生成这两个方法）。
+  - `equals`和`hashCode`方法均会被超类影响，`canEqual`使用`isInstanceOf`，有些人在实现时，使用的是`this.getClass == that.getClass`。
+  - 采用简单hashCode算法，父类的hashCode是直接被累加的。该算法也是`case class`所使用的。
+  - 如果注解所在类已经定义了相同签名的`canEqual`方法，则不会生成该方法。
+
+- 示例
+
+```scala
+@equalsAndHashCode(verbose = true)
+class Person(var name: String, var age: Int)
+```
+
+宏生成的中间代码：
+
+```scala
+class Person extends scala.AnyRef {
+  <paramaccessor> var name: String = _;
+  <paramaccessor> var age: Int = _;
+  def <init>(name: String, age: Int) = {
+    super.<init>();
+    ()
+  };
+  def canEqual(that: Any) = that.isInstanceOf[Person];
+  override def equals(that: Any): Boolean = that match {
+    case (t @ (_: Person)) => t.canEqual(this).$amp$amp(Seq(this.name.equals(t.name), this.age.equals(t.age)).forall(((f) => f))).$amp$amp(true)
+    case _ => false
+  };
+  override def hashCode(): Int = {
+    val state = Seq(name, age);
+    state.map(((x$2) => x$2.hashCode())).foldLeft(0)(((a, b) => 31.$times(a).$plus(b)))
+  }
+}
+```  
\ No newline at end of file

docs/howToUse_en.md

@@ -71,7 +71,7 @@ val ret = TestClass1.builder().i(1).j(0).x("x").build()
 assert(ret.toString == "TestClass1(1,0,x,Some())")
 ```
 
-Compiler macro code:
+Macro expansion code:
 
 ```scala
 object TestClass1 extends scala.AnyRef {
@@ -136,7 +136,7 @@ def getStr(k: Int): String = {
 }
 ```
 
-Compiler macro code:
+Macro expansion code:
 
 ```scala
 // Note that it will not judge whether synchronized already exists, so if synchronized already exists, it will be used twice. 
@@ -194,6 +194,7 @@ The `@constructor` used to generate secondary constructor method for classes, on
     - The internal fields are placed in the first bracket block if constructor is currying.
     - The type of the internal field must be specified, otherwise the macro extension cannot get the type.
       At present, only primitive types and string can be omitted. For example, `var i = 1; var j: int = 1; var k: Object = new Object()` is OK, but `var k = new object()` is not.
+
 - Example
 
 ```scala
@@ -209,11 +210,53 @@ class A2(int: Int, val j: Int, var k: Option[String] = None, t: Option[Long] = S
 println(new A2(1, 2, None, None, 100))
 ```
 
-Compiler macro code(Only constructor def):
+Macro expansion code (Only constructor def):
 
 ```scala
 def <init>(int: Int, j: Int, k: Option[String], t: Option[Long], b: Int) = {
   <init>(int, j, k, t);
   this.b = b
 }
+```
+
+## @equalsAndHashCode
+
+The `@equalsAndHashCode` annotation is used to generate `equals` and `hashCode` methods for ordinary classes, and them takes into account the influence of super classes.
+
+- Note
+    - `verbose` Whether to enable detailed log.
+    - `excludeFields` specifies whether to exclude fields that are not required for the `equals` and `hashCode` methods. Optional, 
+      default is `Nil` (all non private `var` and `val` fields in the class will be used to generate the two methods). 
+    - Both `equals` and `hashCode` methods are affected by super classes, and `canEqual` uses `isInstanceOf` in `equals` method.
+      Some equals implementations use `that.getClass == this.getClass`
+    - It uses simple hashcode algorithm, and the hashcode of the parent class are accumulated directly. The algorithm is also used by `case class`.
+    - If the class of the annotation has already defined the `canEqual` method with the same signature, `canEqual` will not be generated.
+  
+- Example
+
+```scala
+@equalsAndHashCode(verbose = true)
+class Person(var name: String, var age: Int)
+```
+
+Macro expansion code:
+
+```scala
+class Person extends scala.AnyRef {
+  <paramaccessor> var name: String = _;
+  <paramaccessor> var age: Int = _;
+  def <init>(name: String, age: Int) = {
+    super.<init>();
+    ()
+  };
+  def canEqual(that: Any) = that.isInstanceOf[Person];
+  override def equals(that: Any): Boolean = that match {
+    case (t @ (_: Person)) => t.canEqual(this).$amp$amp(Seq(this.name.equals(t.name), this.age.equals(t.age)).forall(((f) => f))).$amp$amp(true)
+    case _ => false
+  };
+  override def hashCode(): Int = {
+    val state = Seq(name, age);
+    state.map(((x$2) => x$2.hashCode())).foldLeft(0)(((a, b) => 31.$times(a).$plus(b)))
+  }
+}
 ```
\ No newline at end of file

src/main/scala/io/github/dreamylost/equalsAndHashCode.scala

+package io.github.dreamylost
+
+import io.github.dreamylost.macros.equalsAndHashCodeMacro
+
+import scala.annotation.{ StaticAnnotation, compileTimeOnly }
+
+/**
+ * annotation to generate equals and hashcode method for classes.
+ *
+ * @author 梦境迷离
+ * @param verbose       Whether to enable detailed log.
+ * @param excludeFields Whether to exclude the specified internal fields.
+ * @since 2021/7/18
+ * @version 1.0
+ */
+@compileTimeOnly("enable macro to expand macro annotations")
+final class equalsAndHashCode(
+    verbose:       Boolean     = false,
+    excludeFields: Seq[String] = Nil
+) extends StaticAnnotation {
+
+  def macroTransform(annottees: Any*): Any = macro equalsAndHashCodeMacro.impl
+}

src/main/scala/io/github/dreamylost/macros/MacroCommon.scala

@@ -115,11 +115,9 @@ trait MacroCommon {
     if (companionOpt.isEmpty) {
       resTree
     } else {
-      val q"$mods object $obj extends ..$bases { ..$body }" = companionOpt.get
-      val companion = q"$mods object $obj extends ..$bases { ..$body }"
       q"""
          $resTree
-         $companion
+         ${companionOpt.get}
          """
     }
   }
@@ -133,7 +131,7 @@ trait MacroCommon {
    * @return Return the result of modifyAction
    */
   def handleWithImplType(c: whitebox.Context)(annottees: c.Expr[Any]*)
-                        (modifyAction: (c.universe.ClassDef, Option[c.universe.ModuleDef]) => Any): c.Expr[Nothing] = {
+    (modifyAction: (c.universe.ClassDef, Option[c.universe.ModuleDef]) => Any): c.Expr[Nothing] = {
     import c.universe._
     annottees.map(_.tree) match {
       case (classDecl: ClassDef) :: Nil => modifyAction(classDecl, None).asInstanceOf[c.Expr[Nothing]]
@@ -168,11 +166,42 @@ trait MacroCommon {
    * @param field
    * @return
    */
-  def fieldTermName(c: whitebox.Context)(field: c.universe.Tree): c.universe.TermName = {
+  def getFieldTermName(c: whitebox.Context)(field: c.universe.Tree): c.universe.TermName = {
     import c.universe._
     field match {
       case q"$mods val $tname: $tpt = $expr" => tname.asInstanceOf[TermName]
       case q"$mods var $tname: $tpt = $expr" => tname.asInstanceOf[TermName]
+      case q"$mods val $pat = $expr"         => pat.asInstanceOf[TermName] //for equalsAndHashcode, need contains all fields.
+      case q"$mods var $pat = $expr"         => pat.asInstanceOf[TermName]
+    }
+  }
+
+  /**
+   * Expand the method params and get the param Name.
+   *
+   * @param c
+   * @param field
+   * @return
+   */
+  def getMethodParamName(c: whitebox.Context)(field: c.universe.Tree): c.universe.Name = {
+    import c.universe._
+    field match {
+      case q"$mods val $tname: $tpt = $expr" => tpt.asInstanceOf[Ident].name.decodedName
+    }
+  }
+
+  /**
+   * Check whether the mods of the fields has a `private[this]`, because it cannot be used in equals method.
+   *
+   * @param c
+   * @param field
+   * @return
+   */
+  def classParamsIsPrivate(c: whitebox.Context)(field: c.universe.Tree): Boolean = {
+    import c.universe._
+    field match {
+      case q"$mods val $tname: $tpt = $expr" => if (mods.asInstanceOf[Modifiers].hasFlag(Flag.PRIVATE)) false else true
+      case q"$mods var $tname: $tpt = $expr" => true
     }
   }
 
@@ -183,7 +212,7 @@ trait MacroCommon {
    * @param annotteeClassParams
    * @return
    */
-  def fieldAssignExpr(c: whitebox.Context)(annotteeClassParams: Seq[c.Tree]): Seq[c.Tree] = {
+  def getFieldAssignExprs(c: whitebox.Context)(annotteeClassParams: Seq[c.Tree]): Seq[c.Tree] = {
     import c.universe._
     annotteeClassParams.map {
       case q"$mods var $tname: $tpt = $expr" => q"$tname: $tpt" //Ignore expr
@@ -202,7 +231,7 @@ trait MacroCommon {
    */
   def modifiedCompanion(c: whitebox.Context)(
     compDeclOpt: Option[c.universe.ModuleDef],
-    codeBlock: c.Tree, className: c.TypeName): c.universe.Tree = {
+    codeBlock:   c.Tree, className: c.TypeName): c.universe.Tree = {
     import c.universe._
     compDeclOpt map { compDecl =>
       val q"$mods object $obj extends ..$bases { ..$body }" = compDecl
@@ -229,11 +258,25 @@ trait MacroCommon {
    * @param c
    * @param annotteeClassDefinitions
    */
-  def getClassMemberValDef(c: whitebox.Context)(annotteeClassDefinitions: Seq[c.Tree]): Seq[c.Tree] = {
+  def getClassMemberValDefs(c: whitebox.Context)(annotteeClassDefinitions: Seq[c.Tree]): Seq[c.Tree] = {
     import c.universe._
     annotteeClassDefinitions.filter(p => p match {
       case _: ValDef => true
-      case _ => false
+      case _         => false
+    })
+  }
+
+  /**
+   * Extract the methods belonging to the class， contains Secondary Constructor.
+   *
+   * @param c
+   * @param annotteeClassDefinitions
+   */
+  def getClassMemberDefDefs(c: whitebox.Context)(annotteeClassDefinitions: Seq[c.Tree]): Seq[c.Tree] = {
+    import c.universe._
+    annotteeClassDefinitions.filter(p => p match {
+      case _: DefDef => true
+      case _         => false
     })
   }
 
@@ -248,7 +291,7 @@ trait MacroCommon {
    */
   def getConstructorWithCurrying(c: whitebox.Context)(typeName: c.TypeName, fieldss: List[List[c.Tree]], isCase: Boolean): c.Tree = {
     import c.universe._
-    val allFieldsTermName = fieldss.map(f => f.map(ff => fieldTermName(c)(ff)))
+    val allFieldsTermName = fieldss.map(f => f.map(ff => getFieldTermName(c)(ff)))
     // not currying
     val constructor = if (fieldss.isEmpty || fieldss.size == 1) {
       q"${if (isCase) q"${typeName.toTermName}(..${allFieldsTermName.flatten})" else q"new $typeName(..${allFieldsTermName.flatten})"}"
@@ -272,7 +315,7 @@ trait MacroCommon {
    */
   def getApplyMethodWithCurrying(c: whitebox.Context)(typeName: c.TypeName, fieldss: List[List[c.Tree]], classTypeParams: List[c.Tree]): c.Tree = {
     import c.universe._
-    val allFieldsTermName = fieldss.map(f => fieldAssignExpr(c)(f))
+    val allFieldsTermName = fieldss.map(f => getFieldAssignExprs(c)(f))
     val returnTypeParams = extractClassTypeParamsTypeName(c)(classTypeParams)
     // not currying
     val applyMethod = if (fieldss.isEmpty || fieldss.size == 1) {

src/main/scala/io/github/dreamylost/macros/constructorMacro.scala

@@ -36,7 +36,7 @@ object constructorMacro extends MacroCommon {
       }
 
       // Extract the internal fields of members belonging to the class， but not in primary constructor.
-      val classFieldDefinitions = getClassMemberValDef(c)(annotteeClassDefinitions)
+      val classFieldDefinitions = getClassMemberValDefs(c)(annotteeClassDefinitions)
       val excludeFields = args._2
 
       /**
@@ -44,7 +44,7 @@ object constructorMacro extends MacroCommon {
        */
       def getClassMemberVarDefOnlyAssignExpr(): Seq[c.Tree] = {
         import c.universe._
-        getClassMemberValDef(c)(annotteeClassDefinitions).filter(_ match {
+        getClassMemberValDefs(c)(annotteeClassDefinitions).filter(_ match {
           case q"$mods var $tname: $tpt = $expr" if !excludeFields.contains(tname.asInstanceOf[TermName].decodedName.toString) => true
           case _ => false
         }).map {
@@ -72,7 +72,7 @@ object constructorMacro extends MacroCommon {
 
       // Extract the field of the primary constructor.
       val ctorFieldNamess = annotteeClassParams.asInstanceOf[List[List[Tree]]]
-      val allFieldsTermName = ctorFieldNamess.map(f => f.map(ff => fieldTermName(c)(ff)))
+      val allFieldsTermName = ctorFieldNamess.map(f => f.map(ff => getFieldTermName(c)(ff)))
 
       /**
        * We generate this method with currying, and we have to deal with the first layer of currying alone.
@@ -80,7 +80,7 @@ object constructorMacro extends MacroCommon {
       def getThisMethodWithCurrying(): c.Tree = {
         // not currying
         // Extract the field of the primary constructor.
-        val classParamsAssignExpr = fieldAssignExpr(c)(ctorFieldNamess.flatten)
+        val classParamsAssignExpr = getFieldAssignExprs(c)(ctorFieldNamess.flatten)
         val applyMethod = if (ctorFieldNamess.isEmpty || ctorFieldNamess.size == 1) {
           q"""
           def this(..${classParamsAssignExpr ++ classFieldDefinitionsOnlyAssignExpr}) = {
@@ -90,7 +90,7 @@ object constructorMacro extends MacroCommon {
           """
         } else {
           // NOTE: currying constructor overload must be placed in the first bracket block.
-          val allClassParamsAssignExpr = ctorFieldNamess.map(cc => fieldAssignExpr(c)(cc))
+          val allClassParamsAssignExpr = ctorFieldNamess.map(cc => getFieldAssignExprs(c)(cc))
           q"""
           def this(..${allClassParamsAssignExpr.head ++ classFieldDefinitionsOnlyAssignExpr})(...${allClassParamsAssignExpr.tail}) = {
             this(..${allFieldsTermName.head})(...${allFieldsTermName.tail})

src/main/scala/io/github/dreamylost/macros/equalsAndHashCodeMacro.scala

+package io.github.dreamylost.macros
+
+import scala.reflect.macros.whitebox
+
+/**
+ *
+ * @author 梦境迷离
+ * @since 2021/7/18
+ * @version 1.0
+ */
+object equalsAndHashCodeMacro extends MacroCommon {
+
+  def impl(c: whitebox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+    import c.universe._
+    val args: (Boolean, Seq[String]) = extractArgumentsTuple2(c) {
+      case q"new equalsAndHashCode(verbose=$verbose)" => (evalTree(c)(verbose.asInstanceOf[Tree]), Nil)
+      case q"new equalsAndHashCode(excludeFields=$excludeFields)" => (false, evalTree(c)(excludeFields.asInstanceOf[Tree]))
+      case q"new equalsAndHashCode(verbose=$verbose, excludeFields=$excludeFields)" => (evalTree(c)(verbose.asInstanceOf[Tree]), evalTree(c)(excludeFields.asInstanceOf[Tree]))
+      case q"new equalsAndHashCode()" => (false, Nil)
+      case _ => c.abort(c.enclosingPosition, ErrorMessage.UNEXPECTED_PATTERN)
+    }
+
+    val annotateeClass: ClassDef = checkAndGetClassDef(c)(annottees: _*)
+    val isCase: Boolean = isCaseClass(c)(annotateeClass)
+    if (isCase) {
+      c.abort(c.enclosingPosition, s"${ErrorMessage.ONLY_CLASS} classDef: $annotateeClass")
+    }
+    val excludeFields = args._2
+
+    def modifiedDeclaration(classDecl: ClassDef, compDeclOpt: Option[ModuleDef] = None): Any = {
+      val (className, annotteeClassParams, annotteeClassDefinitions, superClasses) = classDecl match {
+        case q"$mods class $tpname[..$tparams] $ctorMods(...$paramss) extends { ..$earlydefns } with ..$parents { $self => ..$stats }" =>
+          c.info(c.enclosingPosition, s"modifiedDeclaration className: $tpname, paramss: $paramss", force = args._1)
+          (tpname, paramss, stats.asInstanceOf[Seq[Tree]], parents)
+        case _ => c.abort(c.enclosingPosition, s"${ErrorMessage.ONLY_CLASS} classDef: $classDecl")
+      }
+      val ctorFieldNames = annotteeClassParams.asInstanceOf[List[List[Tree]]].flatten.filter(cf => classParamsIsPrivate(c)(cf))
+      val allFieldsTermName = ctorFieldNames.map(f => getFieldTermName(c)(f))
+
+      c.info(c.enclosingPosition, s"modifiedDeclaration compDeclOpt: $compDeclOpt, ctorFieldNames: $ctorFieldNames, " +
+        s"annotteeClassParams: $superClasses", force = args._1)
+
+      /**
+       * Extract the internal fields of members belonging to the class.
+       */
+      def getClassMemberAllTermName: Seq[c.TermName] = {
+        getClassMemberValDefs(c)(annotteeClassDefinitions).filter(_ match {
+          case q"$mods var $tname: $tpt = $expr" if !excludeFields.contains(tname.asInstanceOf[TermName].decodedName.toString) => true
+          case q"$mods val $tname: $tpt = $expr" if !excludeFields.contains(tname.asInstanceOf[TermName].decodedName.toString) => true
+          case q"$mods val $pat = $expr" if !excludeFields.contains(pat.asInstanceOf[TermName].decodedName.toString) => true
+          case q"$mods var $pat = $expr" if !excludeFields.contains(pat.asInstanceOf[TermName].decodedName.toString) => true
+          case _ => false
+        }).map(f => getFieldTermName(c)(f))
+      }
+
+      val existsCanEqual = getClassMemberDefDefs(c)(annotteeClassDefinitions) exists {
+        case q"$mods def $tname[..$tparams](...$paramss): $tpt = $expr" if tname.toString() == "canEqual" && paramss.nonEmpty =>
+          val params = paramss.asInstanceOf[List[List[Tree]]].flatten.map(pp => getMethodParamName(c)(pp))
+          params.exists(p => p.decodedName.toString == "Any")
+        case _ => false
+      }
+
+      // + super.hashCode
+      val SDKClasses = Set("java.lang.Object", "scala.AnyRef")
+      val canEqualsExistsInSuper = if (superClasses.nonEmpty && !superClasses.forall(sc => SDKClasses.contains(sc.toString()))) { // TODO better way
+        true
+      } else false
+
+      // equals template
+      def ==(termNames: Seq[TermName]): c.universe.Tree = {
+        val getEqualsExpr = (termName: TermName) => {
+          q"this.$termName.equals(t.$termName)"
+        }
+        val equalsExprs = termNames.map(getEqualsExpr)
+        val modifiers = if (canEqualsExistsInSuper) Modifiers(Flag.OVERRIDE, typeNames.EMPTY, List()) else Modifiers(NoFlags, typeNames.EMPTY, List())
+        val canEqual = if (existsCanEqual) q"" else q"$modifiers def canEqual(that: Any) = that.isInstanceOf[$className]"
+        q"""
+        $canEqual
+
+        override def equals(that: Any): Boolean =
+          that match {
+            case t: $className => t.canEqual(this) && Seq(..$equalsExprs).forall(f => f) && ${if (canEqualsExistsInSuper) q"super.equals(that)" else q"true"}
+            case _ => false
+        }
+       """
+      }
+
+      // hashcode template
+      def ##(termNames: Seq[TermName]): c.universe.Tree = {
+        // the algorithm see https://alvinalexander.com/scala/how-to-define-equals-hashcode-methods-in-scala-object-equality/
+        // We use default 1.
+        if (!canEqualsExistsInSuper) {
+          q"""
+         override def hashCode(): Int = {
+            val state = Seq(..$termNames)
+            state.map(_.hashCode()).foldLeft(0)((a, b) => 31 * a + b)
+          }
+          """
+        } else {
+          q"""
+         override def hashCode(): Int = {
+            val state = Seq(..$termNames)
+            state.map(_.hashCode()).foldLeft(0)((a, b) => 31 * a + b) + super.hashCode
+          }
+          """
+        }
+      }
+
+      val allTernNames = allFieldsTermName ++ getClassMemberAllTermName
+      val hashcode = ##(allTernNames)
+      val equals = ==(allTernNames)
+      val equalsAndHashcode =
+        q"""
+          ..$equals
+          $hashcode
+         """
+      // return with object if it exists
+      val resTree = annotateeClass match {
+        case q"$mods class $tpname[..$tparams] $ctorMods(...$paramss) extends { ..$earlydefns } with ..$parents { $self => ..$stats }" =>
+          val originalStatus = q"{ ..$stats }"
+          val append =
+            q"""
+              ..$originalStatus
+              ..$equalsAndHashcode
+             """
+          q"$mods class $tpname[..$tparams] $ctorMods(...$paramss) extends { ..$earlydefns } with ..$parents { $self => ..${append} }"
+      }
+      c.Expr[Any](treeResultWithCompanionObject(c)(resTree, annottees: _*))
+    }
+
+    val resTree = handleWithImplType(c)(annottees: _*)(modifiedDeclaration)
+    printTree(c)(force = args._1, resTree.tree)
+
+    resTree
+  }
+}

src/main/scala/io/github/dreamylost/macros/logMacro.scala

@@ -55,9 +55,9 @@ object logMacro extends MacroCommon {
         treeResultWithCompanionObject(c)(resTree, annottees: _*) //we should return with companion object. Even if we didn't change it.
       case q"$mods object $tpname extends { ..$earlydefns } with ..$parents { $self => ..$stats }" :: _ =>
         q"$mods object $tpname extends { ..$earlydefns } with ..$parents { $self => ..${List(logTree) ::: stats.toList} }"
-        // Note: If a class is annotated and it has a companion, then both are passed into the macro.
-        // (But not vice versa - if an object is annotated and it has a companion class, only the object itself is expanded).
-        // see https://docs.scala-lang.org/overviews/macros/annotations.html
+      // Note: If a class is annotated and it has a companion, then both are passed into the macro.
+      // (But not vice versa - if an object is annotated and it has a companion class, only the object itself is expanded).
+      // see https://docs.scala-lang.org/overviews/macros/annotations.html
     }
 
     printTree(c)(force = args._1, resTree)

src/test/scala/io/github/dreamylost/EmployeeTests.scala

+package io.github.dreamylost
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class EmployeeTests extends AnyFlatSpec with Matchers {
+
+  class Employee(name: String, age: Int, var role: String)
+    extends Person(name, age) {
+    override def canEqual(a: Any): Boolean = a.isInstanceOf[Employee]
+
+    override def equals(that: Any): Boolean =
+      that match {
+        case that: Employee =>
+          that.canEqual(this) &&
+            this.role == that.role &&
+            super.equals(that)
+        case _ => false
+      }
+
+    override def hashCode: Int = {
+      val state = Seq(role)
+      state.map(_.hashCode()).foldLeft(0)((a, b) => 31 * a + b) + super.hashCode
+    }
+
+  }
+
+  class Person(var name: String, var age: Int) {
+
+    // Step 1 - proper signature for `canEqual`
+    // Step 2 - compare `a` to the current class
+    def canEqual(a: Any): Boolean = a.isInstanceOf[Person]
+
+    // Step 3 - proper signature for `equals`
+    // Steps 4 thru 7 - implement a `match` expression
+    override def equals(that: Any): Boolean =
+      that match {
+        case that: Person =>
+          that.canEqual(this) &&
+            this.name == that.name &&
+            this.age == that.age
+        case _ => false
+      }
+
+    // Step 8 - implement a corresponding hashCode c=method
+    override def hashCode: Int = {
+      val state = Seq(name, age)
+      state.map(_.hashCode()).foldLeft(0)((a, b) => 31 * a + b)
+    }
+
+  }
+
+  "equals1" should "ok" in {
+
+    // these first two instances should be equal
+    val nimoy = new Person("Leonard Nimoy", 82)
+    val nimoy2 = new Person("Leonard Nimoy", 82)
+    val shatner = new Person("William Shatner", 82)
+    val stewart = new Person("Patrick Stewart", 47)
+
+    // all tests pass
+    assert(nimoy != null)
+
+    // these should be equal
+    assert(nimoy == nimoy)
+    assert(nimoy == nimoy2)
+    assert(nimoy2 == nimoy)
+
+    // these should not be equal
+    assert(nimoy != shatner)
+    assert(shatner != nimoy)
+    assert(nimoy != "Leonard Nimoy")
+    assert(nimoy != stewart)
+  }
+
+  "equals2" should "ok" in {
+
+    // these first two instance should be equal
+    val eNimoy1 = new Employee("Leonard Nimoy", 82, "Actor")
+    val eNimoy2 = new Employee("Leonard Nimoy", 82, "Actor")
+    val pNimoy = new Person("Leonard Nimoy", 82)
+    val eShatner = new Employee("William Shatner", 82, "Actor")
+
+    // equality tests
+    assert(eNimoy1 == eNimoy1)
+    assert(eNimoy1 == eNimoy2)
+    assert(eNimoy2 == eNimoy1)
+
+    // non-equality tests
+    assert(eNimoy1 != pNimoy)
+    assert(pNimoy != eNimoy1)
+    assert(eNimoy1 != eShatner)
+    assert(eShatner != eNimoy1)
+  }
+
+}

src/test/scala/io/github/dreamylost/EqualsAndHashCodeTest.scala

+package io.github.dreamylost
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+/**
+ *
+ * @author 梦境迷离
+ * @since 2021/7/18
+ * @version 1.0
+ */
+class EqualsAndHashCodeTest extends AnyFlatSpec with Matchers {
+
+  @equalsAndHashCode(verbose = true)
+  @toString
+  class Employee(name: String, age: Int, var role: String) extends Person(name, age)
+
+  @toString
+  @equalsAndHashCode(verbose = true)
+  class Person(var name: String, var age: Int)
+
+  "equals1" should "ok" in {
+    // these first two instances should be equal
+    val nimoy = new Person("Leonard Nimoy", 82)
+    val nimoy2 = new Person("Leonard Nimoy", 82)
+    val shatner = new Person("William Shatner", 82)
+    val stewart = new Person("Patrick Stewart", 47)
+
+    println(nimoy)
+    println(nimoy.hashCode())
+
+    // all tests pass
+    assert(nimoy != null)
+
+    // these should be equal
+    assert(nimoy == nimoy)
+    assert(nimoy == nimoy2)
+    assert(nimoy2 == nimoy)
+
+    // these should not be equal
+    assert(nimoy != shatner)
+    assert(shatner != nimoy)
+    assert(nimoy != "Leonard Nimoy")
+    assert(nimoy != stewart)
+  }
+
+  "equals2" should "ok" in {
+    // these first two instance should be equal
+    val eNimoy1 = new Employee("Leonard Nimoy", 82, "Actor")
+    val eNimoy2 = new Employee("Leonard Nimoy", 82, "Actor")
+    val pNimoy = new Person("Leonard Nimoy", 82)
+    val eShatner = new Employee("William Shatner", 82, "Actor")
+
+    // equality tests
+    assert(eNimoy1 == eNimoy1)
+    assert(eNimoy1 == eNimoy2)
+    assert(eNimoy2 == eNimoy1)
+
+    // non-equality tests
+    assert(eNimoy1 != pNimoy)
+    assert(pNimoy != eNimoy1)
+    assert(eNimoy1 != eShatner)
+    assert(eShatner != eNimoy1)
+
+    println(eNimoy1)
+    println(eNimoy1.hashCode())
+  }
+
+  "equals3" should "ok even if exists a canEqual" in {
+    """
+      |    @equalsAndHashCode
+      |    class Employee(name: String, age: Int, var role: String) extends Person(name, age) {
+      |      override def canEqual(that: Any) = that.getClass == classOf[Employee];
+      |    }
+      |""".stripMargin should compile
+  }
+}