Don't allow self param for implicit method declarations. fixes #71

docs/docs.md

@@ -832,7 +832,7 @@ var n = [Node value: 123, next: none]
 n.incAndPrint()         -- Prints "444"
 ```
 
-Methods can also be declared outside of the type declaration. To distinguish a method from a type function, `self` must be provided as a parameter:
+Methods can be declared outside of the type declaration. When using the flat declaration style, `self` must be the first parameter to distinguish it from a type function:
 ```cy
 func Node.getNext(self):
     return self.next

src/parser.zig

@@ -831,9 +831,10 @@ pub const Parser = struct {
         self.cur_indent = reqIndent;
         defer self.cur_indent = prevIndent;
 
+        var numFields: u32 = 0;
         var firstField = (try self.parseObjectField()) orelse NullId;
-        var numFields: u32 = 1;
         if (firstField != NullId) {
+            numFields += 1;
             var lastField = firstField;
 
             while (true) {

src/sema.zig

@@ -1699,6 +1699,10 @@ fn resolveImplicitMethodDecl(c: *cy.Chunk, parent: *Sym, nodeId: cy.NodeId) !Fun
     var curParamId = header.head.funcHeader.paramHead;
     while (curParamId != cy.NullId) {
         const param = c.nodes[curParamId];
+        const paramName = c.ast.getNodeStringById(param.head.funcParam.name);
+        if (std.mem.eql(u8, "self", paramName)) {
+            return c.reportErrorAt("`self` param is not allowed in an implicit method declaration.", &.{}, curParamId);
+        }
         const typeId = try resolveTypeFromSpecNode(c, param.head.funcParam.typeSpecHead);
         try c.typeStack.append(c.alloc, typeId);
         curParamId = param.next;

test/behavior_test.zig

@@ -44,7 +44,6 @@ const Runner = struct {
     }
 };
 
-// const caseFilter: ?[]const u8 = "call_recursive";
 const caseFilter: ?[]const u8 = null;
 
 // TODO: This could be split into compiler only tests and backend tests.
@@ -137,6 +136,7 @@ if (!aot) {
     run.case("functions/call_typed_param.cy");
     run.case("functions/call_undeclared_error.cy");   
     run.case("functions/declare_over_builtin.cy");
+    run.case("functions/method_self_param_error.cy");
     run.case("functions/object_funcs.cy");
     run.case("functions/overload.cy");
     run.case("functions/read_capture_local_error.cy");

test/functions/method_self_param_error.cy

@@ -0,0 +1,11 @@
+type A:
+    func b(self):
+        pass
+
+--cytest: error
+--CompileError: `self` param is not allowed in an implicit method declaration.
+--
+--main:2:12:
+--    func b(self):
+--           ^
+--