add basic const parsing (needs expr)

- parser: fix main root loop's priming

examples/hello.v

@@ -1 +1,5 @@
-fn main( a int) {}
+const (
+	AWOO = 2
+)
+
+fn main(a int) {}

src/ast.zig

@@ -4,12 +4,14 @@ const Token = tokens.Token;
 
 pub const NodeList = std.ArrayList(*Node);
 pub const ParamList = std.ArrayList(ParamDecl);
+pub const ConstList = std.ArrayList(SingleConst);
 
 // TODO convert FnCall to something like PrefixOp / InfixOp / SuffixOp
 pub const NodeType = enum {
     Root,
     FnDecl,
     FnCall,
+    ConstDecl,
     String,
 };
 
@@ -31,9 +33,17 @@ pub const FnCall = struct {
     arguments: NodeList,
 };
 
+pub const SingleConst = struct {
+    name: Token,
+
+    // TODO expr
+    value: Token,
+};
+
 pub const Node = union(NodeType) {
     Root: NodeList,
     FnDecl: FnDecl,
+    ConstDecl: ConstList,
     FnCall: FnCall,
     String: Token,
 };
@@ -67,11 +77,25 @@ pub fn printNode(node: *Node, ident: usize) void {
                 );
             }
         },
+
+        .ConstDecl => |consts| {
+            print(ident, "ConstDecl ({} consts)\n", consts.len);
+            for (consts.toSlice()) |const_decl| {
+                print(
+                    ident + 1,
+                    "'{}' = '{}'\n",
+                    const_decl.name.lexeme,
+                    const_decl.value.lexeme,
+                );
+            }
+        },
+
         .Root => {
             for (node.Root.toSlice()) |child| {
                 printNode(child, ident + 1);
             }
         },
+
         else => {
             print(ident, "unknown node: {}\n", node);
         },

src/parser.zig

@@ -76,6 +76,7 @@ pub const Parser = struct {
         );
 
         self.tokens[self.tokens.len - 1] = token;
+        std.debug.warn("skip to {}\n", token);
         return token;
     }
 
@@ -87,8 +88,6 @@ pub const Parser = struct {
     }
 
     fn consumeSingle(self: *Parser, ttype: TokenType) !Token {
-        std.debug.warn("consume {}, has {}\n", ttype, self.peek().ttype);
-
         if (self.check(ttype)) {
             var cur = self.peek();
             _ = try self.nextToken();
@@ -122,34 +121,13 @@ pub const Parser = struct {
         return node;
     }
 
+    fn mkConstDecl(self: *Parser, consts: ast.ConstList) !*ast.Node {
+        var node = try self.allocator.create(Node);
+        node.* = Node{ .ConstDecl = consts };
+        return node;
+    }
+
     fn functionDecl(self: *Parser) !*ast.Node {
-        _ = try self.consumeSingle(.Fn);
-        var name = try self.consumeSingle(.Identifier);
-        _ = try self.consumeSingle(.LeftParen);
-
-        var param_list = ast.ParamList.init(self.allocator);
-
-        while (true) {
-            var tok = self.peek();
-
-            switch (tok.ttype) {
-                .RightParen => break,
-                .Identifier => {},
-                else => try self.doError("expected identifier, got {}", tok.ttype),
-            }
-
-            var typetok = try self.nextToken();
-            if (typetok.ttype != .Identifier) {
-                try self.doError("expected identifier for type, got {}", typetok.ttype);
-            }
-
-            var param = try self.allocator.create(ast.ParamDecl);
-            param.* = ast.ParamDecl{ .param_name = tok, .param_type = typetok };
-
-            std.debug.warn("param! {}\n", param);
-            try param_list.append(param);
-            tok = try self.nextToken();
-        }
 
         // function body
         _ = try self.nextToken();
@@ -173,34 +151,6 @@ pub const Parser = struct {
         return try self.mkFnDecl(name, param_list);
     }
 
-    fn functionCall(self: *Parser) !*ast.Node {
-        var identifier = try self.consumeSingle(.Identifier);
-        _ = try self.consumeSingle(.LeftParen);
-
-        // arguments
-        var args = ast.NodeList.init(self.allocator);
-
-        while (true) {
-            var tok = self.peek();
-
-            switch (tok.ttype) {
-                .RightParen => break,
-                .String => blk: {
-                    var node = try self.allocator.create(Node);
-                    node.* = Node{ .String = tok };
-                    try args.append(node);
-                },
-                else => {},
-            }
-
-            tok = try self.nextToken();
-        }
-
-        _ = try self.consumeSingle(.RightParen);
-
-        return Node{ .FnCall = ast.FnCall{ .func_name = identifier, .arguments = args } };
-    }
-
     fn processToken(self: *Parser, token: Token) anyerror!*ast.Node {
         var node = switch (token.ttype) {
             .Fn => try self.functionDecl(),
@@ -216,8 +166,6 @@ pub const Parser = struct {
 
     fn block(self: *Parser) anyerror!*ast.Node {
 
-        // TODO if(self.accept(.Const))
-
         // while receiving functions, process more
         while (self.accept(.Fn)) {
             try self.consumeSingle(.LeftParen);
@@ -228,35 +176,67 @@ pub const Parser = struct {
         self.statement();
     }
 
+    fn fnDecl(self: *@This()) !?*Node {
+        var param_list = ast.ParamList.init(self.allocator);
+        errdefer param_list.deinit();
+
+        _ = try self.consumeSingle(.Fn);
+        var name = try self.consumeSingle(.Identifier);
+
+        _ = try self.consumeSingle(.LeftParen);
+
+        while (self.peek().ttype != .RightParen) {
+            const param_name = try self.consumeSingle(.Identifier);
+            const param_type = try self.consumeSingle(.Identifier);
+
+            try param_list.append(ast.ParamDecl{
+                .name = param_name,
+                .typ = param_type,
+            });
+        }
+
+        _ = try self.consumeSingle(.RightParen);
+
+        _ = try self.consumeSingle(.LeftBrace);
+        // TODO block
+        _ = try self.consumeSingle(.RightBrace);
+
+        std.debug.warn("!fn name: {}\n", name);
+        return try self.mkFnDecl(name, param_list);
+    }
+
+    fn constDecl(self: *@This()) !?*Node {
+        var consts = ast.ConstList.init(self.allocator);
+        errdefer consts.deinit();
+
+        _ = try self.consumeSingle(.Const);
+
+        _ = try self.consumeSingle(.LeftParen);
+
+        while (self.peek().ttype != .RightParen) {
+            const const_name = try self.consumeSingle(.Identifier);
+            _ = try self.consumeSingle(.Equal);
+
+            // TODO expr
+            const const_value = self.peek();
+            _ = try self.nextToken();
+            //const const_value = try self.consumeSingle(.Identifier);
+
+            try consts.append(ast.SingleConst{ .name = const_name, .value = const_value });
+        }
+
+        _ = try self.consumeSingle(.RightParen);
+
+        return self.mkConstDecl(consts);
+    }
+
     fn topDecl(self: *@This()) !?*Node {
         return switch (self.peek().ttype) {
-            .Fn => blk: {
+            .Fn => try self.fnDecl(),
-                var param_list = ast.ParamList.init(self.allocator);
+            .Const => try self.constDecl(),
-                errdefer param_list.deinit();
 
-                _ = try self.consumeSingle(.Fn);
-                var name = try self.consumeSingle(.Identifier);
-
-                _ = try self.consumeSingle(.LeftParen);
-
-                while (self.peek().ttype != .RightParen) {
-                    const param_name = try self.consumeSingle(.Identifier);
-                    const param_type = try self.consumeSingle(.Identifier);
-
-                    try param_list.append(ast.ParamDecl{ .name = param_name, .typ = param_type });
-                }
-
-                _ = try self.consumeSingle(.RightParen);
-
-                _ = try self.consumeSingle(.LeftBrace);
-                // TODO block
-                _ = try self.consumeSingle(.RightBrace);
-
-                std.debug.warn("!fn name: {}\n", name);
-                break :blk try self.mkFnDecl(name, param_list);
-            },
             else => |ttype| blk: {
-                self.doError("expected fn, got {}\n", ttype);
+                self.doError("(basic) expected fn/const, got {}\n", ttype);
                 break :blk null;
             },
         };
@@ -266,8 +246,16 @@ pub const Parser = struct {
         self.tokens = try self.allocator.alloc(Token, 0);
         var root = try ast.mkRoot(self.allocator);
 
+        var token_opt: ?Token = null;
+
         while (true) {
-            var token = try self.nextToken();
+            if (token_opt == null) {
+                token_opt = try self.nextToken();
+            } else {
+                token_opt = self.peek();
+            }
+
+            var token = token_opt.?;
             if (token.ttype == .EOF) break;
 
             var node = try self.topDecl();