fix #11 and private visibility for constructor params, fields and methods.

.gitignore

@@ -13,3 +13,4 @@ xcuserdata
 *.gpg
 .gigaide
 /kotlin-js-store/yarn.lock
+/test.lyng

docs/OOP.md

@@ -1,12 +1,19 @@
 # OO implementation in Lyng
 
-Short introduction
+## Declaration 
+
+The class clause looks like
+
+    class Point(x,y)
+    assert( Point is Class ) 
+    >>> void
+
+It creates new `Class` with two fields. Here is the more practical sample:
 
     class Point(x,y) {
         fun length() { sqrt(x*x + y*y) } 
     }
 
-    assert( Point is Class )
     val p = Point(3,4)
     assert(p is Point)
     assertEquals(5, p.length())
@@ -32,7 +39,111 @@ Form now on `Point` is a class, it's type is `Class`, and we can create instance
 example above.
 
 Class point has a _method_, or a _member function_ `length()` that uses its _fields_ `x` and `y` to
-calculate the magnitude.
+calculate the magnitude. Length is called
+
+### default values in constructor
+
+Constructor arguments are the same as function arguments except visibility
+statements discussed later, there could be default values, ellipsis, etc.
+
+    class Point(x=0,y=0) 
+    val p = Point()
+    assert( p.x == 0 && p.y == 0 )
+    >>> void
+
+## Methods
+
+Functions defined inside a class body are methods, and unless declared
+`private` are available to be called from outside the class:
+
+    class Point(x,y) {
+        // public method declaration:
+        fun length() { sqrt(d2()) }
+
+        // private method:
+        private fun d2() {x*x + y*y}
+    }
+    val p = Point(3,4)
+    // private called from inside public: OK
+    assertEquals( 5, p.length() )
+    // but us not available directly
+    assertThrows() { p.d2() }
+    void
+    >>> void
+
+## fields and visibility
+
+It is possible to add non-constructor fields:
+
+    class Point(x,y) {
+        fun length() { sqrt(x*x + y*y) } 
+    
+        // set at construction time:   
+        val initialLength = length()
+    }
+    val p = Point(3,4)
+    p.x = 3
+    p.y = 0
+    assertEquals( 3, p.length() )
+    // but initial length could not be changed after as declard val:
+    assert( p.initialLength == 5 )
+    >>> void
+
+### Mutable fields
+
+Are declared with var
+
+    class Point(x,y) {
+        var isSpecial = false
+    }
+    val p = Point(0,0)
+    assert( p.isSpecial == false )
+
+    p.isSpecial = true
+    assert( p.isSpecial == true )
+    >>> void
+
+### Private fields
+
+Private fields are visible only _inside the class instance_:
+
+    class SecretCounter {
+        private var count = 0
+        
+        fun increment() {
+            count++
+            void // hide counter
+        }
+        
+        fun isEnough() {
+            count > 10
+        }
+    }
+    val c = SecretCounter()
+    assert( c.isEnough() == false )
+    assert( c.increment() == void )
+    for( i in 0..10 ) c.increment()
+    assert( c.isEnough() )
+
+    // but the count is not available outside:
+    assertThrows() { c.count }
+    void
+    >>> void
+
+It is possible to provide private constructor parameters so they can be
+set at construction but not available outside the class:
+
+    class SecretCounter(private var count = 0) {
+        // ...
+    }
+    val c = SecretCounter(10)
+    assertThrows() { c.count }
+    void
+    >>> void
+
+
+
+# Theory
 
 ## Basic principles:
 

library/src/commonMain/kotlin/net/sergeych/lyng/ArgsDeclaration.kt

@@ -23,10 +23,12 @@ data class ArgsDeclaration(val params: List<Item>, val endTokenType: Token.Type)
     suspend fun assignToContext(
         context: Context,
         fromArgs: Arguments = context.args,
-        defaultAccessType: Compiler.AccessType = Compiler.AccessType.Var
+        defaultAccessType: Compiler.AccessType = Compiler.AccessType.Var,
+        defaultVisibility: Compiler.Visibility = Compiler.Visibility.Public
     ) {
         fun assign(a: Item, value: Obj) {
-            context.addItem(a.name, (a.accessType ?: defaultAccessType).isMutable, value)
+            context.addItem(a.name, (a.accessType ?: defaultAccessType).isMutable, value,
+                a.visibility ?: defaultVisibility)
         }
 
         suspend fun processHead(index: Int): Int {

library/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt

@@ -37,6 +37,13 @@ class Compiler(
                         }
                 }
 
+                Token.Type.PRIVATE, Token.Type.PROTECTED -> {
+                    if(cc.nextIdValue() in setOf("var", "val", "class", "fun", "fn")) {
+                        continue
+                    } else
+                        throw ScriptError(t.pos, "unexpected keyword ${t.value}")
+                }
+
                 Token.Type.PLUS2, Token.Type.MINUS2 -> {
                     cc.previous()
                     parseExpression(cc)
@@ -408,7 +415,7 @@ class Compiler(
     }
 
     enum class Visibility {
-        Public, Private, Protected, Internal
+        Public, Private, Protected//, Internal
     }
 
     /**
@@ -429,43 +436,16 @@ class Compiler(
                 }
 
                 Token.Type.NEWLINE -> {}
+                Token.Type.PROTECTED, Token.Type.PRIVATE -> {
+                    if (!isClassDeclaration) {
+                        cc.restorePos(startPos); return null
+                    }
+                }
                 Token.Type.ID -> {
                     // visibility
-                    val visibility = when (t.value) {
+                    val visibility = if( isClassDeclaration )
-                        "private" -> {
+                        cc.getVisibility(Visibility.Public)
-                            if (!isClassDeclaration) {
+                    else Visibility.Public
-                                cc.restorePos(startPos); return null
-                            }
-                            t = cc.next()
-                            Visibility.Private
-                        }
-
-                        "protected" -> {
-                            if (!isClassDeclaration) {
-                                cc.restorePos(startPos); return null
-                            }
-                            t = cc.next()
-                            Visibility.Protected
-                        }
-
-                        "internal" -> {
-                            if (!isClassDeclaration) {
-                                cc.restorePos(startPos); return null
-                            }
-                            t = cc.next()
-                            Visibility.Internal
-                        }
-
-                        "public" -> {
-                            if (!isClassDeclaration) {
-                                cc.restorePos(startPos); return null
-                            }
-                            t = cc.next()
-                            Visibility.Public
-                        }
-
-                        else -> null
-                    }
                     // val/var?
                     val access = when (t.value) {
                         "val" -> {
@@ -703,7 +683,7 @@ class Compiler(
         val nameToken = cc.requireToken(Token.Type.ID)
         val constructorArgsDeclaration =
             if (cc.skipTokenOfType(Token.Type.LPAREN, isOptional = true))
-                parseArgsDeclaration(cc)
+                parseArgsDeclaration(cc, isClassDeclaration = true)
             else null
 
         if (constructorArgsDeclaration != null && constructorArgsDeclaration.endTokenType != Token.Type.RPAREN)
@@ -752,7 +732,9 @@ class Compiler(
                     }
                     Visibility.Protected ->
                         thisObj.protectedFields += name
-                    else -> {
+
+                    Visibility.Private -> {
+                        //println("private field: $name")
                     }
                 }
             }
@@ -762,20 +744,6 @@ class Compiler(
         // inheritance must alter this code:
         val newClass = ObjClass(className).apply {
             instanceConstructor = constructorCode
-            constructorArgsDeclaration?.let { cad ->
-                // we need accessors for all fields:
-                for (f in cad.params) {
-                    createField(
-                        f.name,
-                        statement {
-                            val context = (thisObj as ObjInstance).instanceContext
-                            context[f.name]?.value ?: raiseError("field is not initialized: ${f.name}")
-                        },
-                        true,
-//                        (f.accessType ?: defaultAccess).isMutable,
-                    )
-                }
-            }
         }
 
         return statement {
@@ -1100,6 +1068,8 @@ class Compiler(
     }
 
     private fun parseFunctionDeclaration(tokens: CompilerContext): Statement {
+        val visibility = tokens.getVisibility()
+
         var t = tokens.next()
         val start = t.pos
         val name = if (t.type != Token.Type.ID)
@@ -1136,7 +1106,7 @@ class Compiler(
             // we added fn in the context. now we must save closure
             // for the function
             closure = context
-            context.addItem(name, false, fnBody)
+            context.addItem(name, false, fnBody, visibility)
             // as the function can be called from anywhere, we have
             // saved the proper context in the closure
             fnBody
@@ -1162,6 +1132,14 @@ class Compiler(
     }
 
     private fun parseVarDeclaration(kind: String, mutable: Boolean, tokens: CompilerContext): Statement {
+        // we are just after var/val, visibility if exists is 2 steps behind
+        val visibility = when( tokens.atOffset(-2)?.type ) {
+            Token.Type.PRIVATE ->
+                Visibility.Private
+            Token.Type.PROTECTED -> Visibility.Protected
+            else -> Visibility.Public
+        }
+
         val nameToken = tokens.next()
         val start = nameToken.pos
         if (nameToken.type != Token.Type.ID)
@@ -1190,7 +1168,7 @@ class Compiler(
             // create a separate copy:
             val initValue = initialExpression?.execute(context)?.byValueCopy() ?: ObjNull
 
-            context.addItem(name, mutable, initValue)
+            context.addItem(name, mutable, initValue, visibility)
             ObjVoid
         }
     }

library/src/commonMain/kotlin/net/sergeych/lyng/CompilerContext.kt

@@ -9,7 +9,7 @@ internal class CompilerContext(val tokens: List<Token>) {
     var loopLevel = 0
         private set
 
-    inline fun <T> parseLoop(f: () -> T): Pair<Boolean,T> {
+    inline fun <T> parseLoop(f: () -> T): Pair<Boolean, T> {
         if (++loopLevel == 0) breakFound = false
         val result = f()
         return Pair(breakFound, result).also {
@@ -98,4 +98,40 @@ internal class CompilerContext(val tokens: List<Token>) {
         breakFound = true
     }
 
+    /**
+     * Return value of the next token if it is an identifier, null otherwise.
+     * Does not change position.
+     */
+    fun nextIdValue(): String? {
+        return if (hasNext()) {
+            val nt = tokens[currentIndex]
+            if (nt.type == Token.Type.ID)
+                nt.value
+            else null
+        } else null
+    }
+
+    @Suppress("unused")
+    fun current(): Token = tokens[currentIndex]
+
+    /**
+     * If the token at current position plus offset (could be negative) exists, returns it, otherwise returns null.
+     */
+    fun atOffset(offset: Int): Token? =
+        if (currentIndex + offset in tokens.indices) tokens[currentIndex + offset] else null
+
+    /**
+     * Scan backwards as deep as specified looking for visibility token. Does not change position.
+     */
+    fun getVisibility(default: Compiler.Visibility = Compiler.Visibility.Public, depths: Int = 2): Compiler.Visibility {
+        for( i in -depths .. -1) {
+            when( atOffset(i)?.type) {
+                Token.Type.PROTECTED -> return Compiler.Visibility.Protected
+                Token.Type.PRIVATE -> return Compiler.Visibility.Private
+                else -> {}
+            }
+        }
+        return default
+    }
+
 }

library/src/commonMain/kotlin/net/sergeych/lyng/Context.kt

@@ -28,7 +28,8 @@ class Context(
     fun raiseClassCastError(msg: String): Nothing = raiseError(ObjClassCastError(this, msg))
 
     @Suppress("unused")
-    fun raiseSymbolNotFound(name: String): Nothing = raiseError(ObjSymbolNotDefinedError(this, "symbol is not defined: $name"))
+    fun raiseSymbolNotFound(name: String): Nothing =
+        raiseError(ObjSymbolNotDefinedError(this, "symbol is not defined: $name"))
 
     fun raiseError(message: String): Nothing {
         throw ExecutionError(ObjError(this, message))
@@ -73,8 +74,13 @@ class Context(
 
     fun copy() = Context(this, args, pos, thisObj)
 
-    fun addItem(name: String, isMutable: Boolean, value: Obj): ObjRecord {
+    fun addItem(
-        return ObjRecord(value, isMutable).also { objects.put(name, it) }
+        name: String,
+        isMutable: Boolean,
+        value: Obj,
+        visibility: Compiler.Visibility = Compiler.Visibility.Public
+    ): ObjRecord {
+        return ObjRecord(value, isMutable, visibility).also { objects.put(name, it) }
     }
 
     fun getOrCreateNamespace(name: String): ObjClass {

library/src/commonMain/kotlin/net/sergeych/lyng/Parser.kt

@@ -280,6 +280,8 @@ private class Parser(fromPos: Pos) {
                         when (text) {
                             "in" -> Token("in", from, Token.Type.IN)
                             "is" -> Token("is", from, Token.Type.IS)
+                            "protected" -> Token("protected", from, Token.Type.PROTECTED)
+                            "private" -> Token("private", from, Token.Type.PRIVATE)
                             else -> Token(text, from, Token.Type.ID)
                         }
                 } else

library/src/commonMain/kotlin/net/sergeych/lyng/Token.kt

@@ -17,6 +17,8 @@ data class Token(val value: String, val pos: Pos, val type: Type) {
         AND, BITAND, OR, BITOR, NOT, BITNOT, DOT, ARROW, QUESTION, COLONCOLON,
         SINLGE_LINE_COMMENT, MULTILINE_COMMENT,
         LABEL, ATLABEL, // label@ at@label
+        PRIVATE, PROTECTED,
+        //PUBLIC, PROTECTED, INTERNAL, EXPORT, OPEN, INLINE, OVERRIDE, ABSTRACT, SEALED, EXTERNAL, VAL, VAR, CONST, TYPE, FUN, CLASS, INTERFACE, ENUM, OBJECT, TRAIT, THIS,
         ELLIPSIS, DOTDOT, DOTDOTLT,
         NEWLINE,
         EOF,

library/src/commonTest/kotlin/ScriptTest.kt

@@ -1453,4 +1453,15 @@ class ScriptTest {
             assertEquals(sqrt(109), p.length())
             """.trimIndent())
     }
+
+    @Test
+    fun testPrivateConstructorParams() = runTest {
+        val c = Context()
+        c.eval("""
+            class Point(private var x,y)
+            val p = Point(1,2)
+            p.y = 101
+            assertThrows() { p.x = 10 }
+            """)
+    }
 }