Ticket #102: properties-init.patch

Source/Members.cobra

@@ -443 +443 @@
     is partial
     inherits BoxField
     """
-    A constanst such as:
+    A constant such as:
         const PI = 3.14
     
     In practice, when developing libraries, a read-only var is more practical than a constant,
@@ -519 +519 @@
         else
             return false
 
+    # used in property declaration when providing an initial value for an existing backing var
+    def setInitExpr(initExpr as Expr) as bool
+        if _initExpr
+            return false
+        _initExpr = initExpr
+        return true 
+
     ## INamedNode
 
     get typeForReceiver as IType is override

Source/CobraParser.cobra

@@ -269 +269 @@
         while .optional('EOL'), pass
         .expect('DEDENT')
 
-    def indentIsDeclNames as List<of String>
-        """
-        Parses indentation followed by "is" names, or "is" names followed by indentation.
-        Example 1:
-            def main is shared
-                pass
-        Example 2:
-            def main
-                is shared
-                pass
-        In either case, returns the list of "is" names or nil if there were none.
-        """
-        if .peek.which=='IS'
-            isNames = .isDeclNames
-            .expect('INDENT')
-            return isNames
-        else
-            if .optionalIndent
-                return .isDeclNames
-            else
-                .expect('INDENT')
-                return List<of String>()
-
     def optionalIndent as IToken?
         """
         Consumes and warns about COLON not being necessary.
@@ -593 +570 @@
             ['private', 'shared']
         Errors:
             TODO
-        Used by: classDecl, interfaceDecl, enumDecl, indentIsDeclNames
+        Used by: classDecl, interfaceDecl, enumDecl
         """
         if _validIsNames is nil
             _validIsNames = ['fake', 'extern', 'shared', 'virtual', 'nonvirtual', 'override', 'new', 'public', 'protected', 'private', 'internal', 'abstract', 'partial']
+        hasIsNames = false
+        names = _isDeclNamesNoEOL(out hasIsNames)
+        if hasIsNames, .endOfLine
+        # TODO: error on virtual and override
+        # TODO: error on virtual and shared
+        # TODO: error if 2 or more of 'public', 'protected', 'private', 'internal'
+        return names
+        
+    def _isDeclNamesNoEOL(hasIsNames as out bool) as List<of String>
+        """ Parse for possible stream of isNames without terminating EOL """
+        require _validIsNames is not nil
         names = List<of String>(_isNamesStack)
+        hasIsNames = false
         if .optional('IS') is nil
             return names
+        hasIsNames = true
         while true
             what = .grab.text
             if what in _validIsNames
@@ -613 +603 @@
                 if .peek.text in _validIsNames
                     .throwError(.peek, 'Multiple access modifiers should be separated by commas such as "[what], [.peek.text]".')
                 break
-        .endOfLine
-        # TODO: error on virtual and override
-        # TODO: error on virtual and shared
-        # TODO: error if 2 or more of 'public', 'protected', 'private', 'internal'
         return names
+        
 
     def declGenericParams(token as IToken) as List<of GenericParam>
         """
@@ -1397 +1384 @@
         else
             varName = .expect('ID').text
         declVarType = if(.optional('AS'), .typeId, nil)
-        if declVarType
-            varDef = BoxVar(token, .curBox, varName, declVarType, List<of String>(_isNamesStack), nil, nil, 'Automatic backing var for property "[name]".')
-            .curBox.addDecl(varDef)
-        else
-            possibleVarDef = .curBox.declForName(varName)
-            if possibleVarDef is nil
-                .throwError('There is no variable named "[varName]" to match the property "[name]".')
-            if possibleVarDef inherits BoxVar
-                varDef = possibleVarDef
-            else
-                .throwError('A property can only cover for variables. [varName] is a [possibleVarDef]')  # TODO: .englishName?
         if .curBox inherits Interface
             .throwError('Cannot use the "from" form of a property inside an interface declaration.')
         if .peek.which == 'IS'
-            isNames = .isDeclNames
-            hasIsNames = true
-            indent = .optional('INDENT')
-        else
-            indent = .optionalIndent        
-        if indent
+            hasIsNames = false
+            isNames = _isDeclNamesNoEOL(out hasIsNames)
+        if .optional('ASSIGN')
+            initExpr = .expression to ?
+        .endOfLine
+        if .optional('INDENT')
             if not hasIsNames, isNames = .isDeclNames
             attribs = .hasAttribs
             docString = .docString
@@ -1425 +1401 @@
             if not hasIsNames, isNames = List<of String>(_isNamesStack)
             attribs = AttributeList()
             docString = ''
+        varDef = _genVarDef(declVarType, token, name, varName, initExpr)
         return Property(token, .curBox, name, isNames, attribs, varDef, coverWhat, docString)
-
+        
+    def _genVarDef(declVarType as ITypeProxy?, token as IToken, name as String, varName as String, initExpr as Expr?) as BoxVar
+        """ Find existing backing variable for property or make one and return it.""" 
+        possibleVarDef = .curBox.declForName(varName)
+        if not possibleVarDef
+            if not initExpr and not declVarType
+                .throwError('There is no variable named "[varName]" to match the property "[name]".')
+            varDef = BoxVar(token, .curBox, varName, declVarType, List<of String>(_isNamesStack), initExpr, nil, 'Automatic backing var for property "[name]".')
+            .curBox.addDecl(varDef)
+            return varDef
+                
+        if  possibleVarDef inherits BoxVar
+            varDef = possibleVarDef
+        else
+            .throwError('A property can only cover for variables. [varName] is a [possibleVarDef]')  # TODO: .englishName?
+        if initExpr and not varDef.setInitExpr(initExpr to !)   
+            .throwError('Property backing variable "[varName]" has already been initialised') # include line# of backing variable decl
+        return varDef
+            
     def declareGetOnlyProperty as ProperDexer?
         return _declareGetOrSetOnlyProperty(0)
 

Tests/120-classes/505-properties-from-init-error.cobra

@@ +1 @@
+# Properties init backing variable
+class PropInit
+
+    var _x as int = 22
+    get x from var = 95  
+                        # .error. already been initialised
+    def main is shared
+        pass

Tests/120-classes/505-properties-from-init-1.cobra

@@ +1 @@
+# Properties implicitly create and init backing variable
+class PropInit
+
+    var _x as int
+    var _y = 99
+    var _y1 = 99
+    
+    # existing backing var
+    get x from var = 90 
+    get y1 from var as int8  # type is redundant as set in backing var so ignored
+    
+    # implicitly generate and init backing var
+    get z0 from var as int
+    get z from var as int = 100  # explicitly set type and init
+    get z1 from var as int is protected # explicitly set type and modifier
+    get z2 from var as int is protected = 101  # type, mod + init expr
+    get z3 from var = 103  # infer type fm init expr
+
+    def main is shared
+        x = PropInit()
+        assert x.x == 90
+        assert x.y1 == 99
+        
+        assert x.z0 == 0
+        
+        assert x.z == 100   
+        assert x.z1 == 0 # not initted
+        assert x.z2 == 101
+        assert x.z3 == 103

Tests/120-classes/505-properties-from-init.cobra

@@ +1 @@
+class Point
+
+    def init
+        _x += 1
+        __y += 1
+
+    get x from var as int = 100   # typical property with matching var backing
+    
+    # test explicit naming of the var. 
+    # note that __y will be private 
+    get y from __y = 101
+    
+    pro z from var = 201
+
+    set z0 from var = 300
+    
+    def moveBy(dx as int, dy as int)
+        _x += dx
+        __y += dy
+    
+    def chk
+        assert _x == 101
+        assert .x == _x
+    
+        assert __y == 102
+        assert .y == __y
+    
+        assert _z == 222
+        assert .z == _z
+        
+        assert _z0 == 300
+        
+    def main is shared  
+        p = Point()
+        assert p.x == 101
+        assert p.y == 102
+        
+        assert p.z == 201
+        p.z = 222
+        assert p.z == 222
+        p.chk
+        

Developer/IntermediateReleaseNotes.text

@@ -11 +11 @@
 
 * Support constant declarations on class instance variables. ticket:122
 
+* Allow property declarations to set an initial value (on property backing 
+  variable). ticket:102
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