add if statements

- ast: make FnDecl and Const print better as s-expressions

examples/hello.v

@@ -11,4 +11,10 @@ fn main(a int) int {
 	3 / (51 + 2)
 	mut a := 1+2
 	a = 2
+
+	if a {
+		println(30)
+	} else {
+		println(50)
+	}
 }

src/ast.zig

@@ -20,14 +20,13 @@ pub const NodeType = enum {
 
 pub const ParamDecl = struct {
     name: Token,
-
-    // TODO types
     typ: Token,
 };
 
 pub const FnDecl = struct {
     func_name: Token,
     params: ParamList,
+    return_type: Token,
     body: StmtList,
 };
 
@@ -80,32 +79,51 @@ pub const VarDecl = struct {
 pub const Expr = union(ExprType) {
     Assign: AssignExpr,
     VarDecl: VarDecl,
+
     Binary: BinaryExpr,
     Unary: UnaryExpr,
     Literal: LiteralExpr,
+
     Variable: Token,
     Grouping: *Expr,
 };
 
-// TODO
-//pub const IfStmt = struct {
-//    condition: *Expr,
-//    then_branch: *StmtList,
-//    else_branch: *StmtList,
-//};
+pub const IfBranch = std.ArrayList(*Stmt);
+
+pub const IfStmt = struct {
+    condition: *Expr,
+    then_branch: IfBranch,
+    else_branch: ?IfBranch,
+};
 
 pub const Stmt = union(enum) {
     Expr: *Expr,
     Println: *Expr,
 
-    // TODO
-    //If: IfStmt,
+    If: IfStmt,
 
     pub fn mkPrintln(allocator: *std.mem.Allocator, expr: *Expr) !*Stmt {
         var println = try allocator.create(Stmt);
         println.* = Stmt{ .Println = expr };
         return println;
     }
+
+    pub fn mkIfStmt(
+        allocator: *std.mem.Allocator,
+        condition: *Expr,
+        then: IfBranch,
+        else_branch: ?IfBranch,
+    ) !*Stmt {
+        var println = try allocator.create(Stmt);
+        println.* = Stmt{
+            .If = IfStmt{
+                .condition = condition,
+                .then_branch = then,
+                .else_branch = else_branch,
+            },
+        };
+        return println;
+    }
 };
 
 pub const Node = union(NodeType) {
@@ -137,39 +155,50 @@ fn print(ident: usize, comptime fmt: []const u8, args: ...) void {
     std.debug.warn(fmt, args);
 }
 
+fn printBlock(ident: usize, block: var, endNewline: bool) void {
+    std.debug.warn("(\n");
+
+    for (block.toSlice()) |stmt| {
+        printIdent(ident);
+        printStmt(ident, stmt);
+        std.debug.warn("\n");
+    }
+
+    if (endNewline) {
+        print(ident - 1, ")\n");
+    } else {
+        print(ident - 1, ")");
+    }
+}
+
 pub fn printNode(node: *Node, ident: usize) void {
     switch (node.*) {
         .FnDecl => |decl| {
-            print(ident, "FnDecl name='{}'\n", decl.func_name.lexeme);
+            print(ident, "(fn {} (", decl.func_name.lexeme);
 
             for (decl.params.toSlice()) |param| {
-                print(
-                    ident + 1,
-                    "param: '{}' {}\n",
-                    param.name.lexeme,
-                    param.typ.lexeme,
-                );
+                std.debug.warn("({} {}) ", param.name.lexeme, param.typ.lexeme);
             }
 
-            for (decl.body.toSlice()) |stmt| {
-                printIdent(ident + 1);
-                printStmt(stmt);
-                std.debug.warn("\n");
-            }
+            printBlock(ident + 1, decl.body, false);
+            std.debug.warn(")\n");
         },
 
         .ConstDecl => |consts| {
-            print(ident, "ConstDecl ({} consts)\n", consts.len);
+            print(ident, "(const (\n");
+
             for (consts.toSlice()) |const_decl| {
                 print(
                     ident + 1,
-                    "{} = ",
+                    "({} ",
                     const_decl.name.lexeme,
                 );
 
                 printExpr(const_decl.expr);
-                std.debug.warn("\n");
+                std.debug.warn(")\n");
             }
+
+            print(ident, "))\n");
         },
 
         .Root => {
@@ -186,7 +215,7 @@ pub fn printNode(node: *Node, ident: usize) void {
 
         .Stmt => |stmt| blk: {
             printIdent(ident);
-            printStmt(stmt);
+            printStmt(ident, stmt);
             std.debug.warn("\n");
         },
 
@@ -247,10 +276,24 @@ pub fn printExpr(expr: *Expr) void {
     }
 }
 
-pub fn printStmt(stmt: *Stmt) void {
+pub fn printStmt(ident: usize, stmt: *Stmt) void {
     switch (stmt.*) {
         .Println => |expr| parenthetize("println", &[_]*Expr{expr}),
         .Expr => |expr| printExpr(expr),
+
+        .If => |ifstmt| {
+            std.debug.warn("(if ");
+            printExpr(ifstmt.condition);
+            std.debug.warn(" ");
+
+            printBlock(ident + 1, ifstmt.then_branch, false);
+            if (ifstmt.else_branch) |else_branch| {
+                std.debug.warn(" else ");
+                printBlock(ident + 1, else_branch, false);
+            }
+
+            std.debug.warn(")\n");
+        },
         else => std.debug.warn("UnknownStmt-{}", @tagName(stmt.*)),
     }
 }

src/parser.zig

@@ -120,12 +120,19 @@ pub const Parser = struct {
         return false;
     }
 
-    fn mkFnDecl(self: *Parser, name: Token, params: ast.ParamList, block: ast.StmtList) !*ast.Node {
+    fn mkFnDecl(
+        self: *Parser,
+        name: Token,
+        params: ast.ParamList,
+        return_type: Token,
+        block: ast.StmtList,
+    ) !*ast.Node {
         var node = try self.allocator.create(Node);
         node.* = Node{
             .FnDecl = ast.FnDecl{
                 .func_name = name,
                 .params = params,
+                .return_type = return_type,
                 .body = block,
             },
         };
@@ -348,6 +355,8 @@ pub const Parser = struct {
 
         while (self.peek().ttype != .RightParen) {
             const param_name = try self.consumeSingle(.Identifier);
+
+            // TODO dedicated function to consume a type
             const param_type = try self.consumeSingle(.Identifier);
 
             try param_list.append(ast.ParamDecl{
@@ -358,13 +367,10 @@ pub const Parser = struct {
 
         _ = try self.consumeSingle(.RightParen);
 
-        // TODO return type
+        // TODO dedicated function to consume a type
         const return_type = try self.consumeSingle(.Identifier);
-
-        var block = try self.parseBlock();
-
-        std.debug.warn("!fn name: {}\n", name);
-        return try self.mkFnDecl(name, param_list, block.Block);
+        var block_node = try self.parseBlock();
+        return try self.mkFnDecl(name, param_list, return_type, block_node.Block);
     }
 
     fn parseConstDecl(self: *@This()) !?*Node {
@@ -413,7 +419,6 @@ pub const Parser = struct {
         _ = try self.consumeSingle(.LeftBrace);
 
         while (self.peek().ttype != .RightBrace) {
-            std.debug.warn("get smt with cur {}\n", self.peek().ttype);
             var stmt = try self.parseDecl();
             ast.printNode(try self.mkStmt(stmt), 0);
             try stmts.append(stmt);
@@ -430,6 +435,7 @@ pub const Parser = struct {
 
     fn parseStmt(self: *@This()) anyerror!*Stmt {
         return switch (self.peek().ttype) {
+            .If => try self.parseIfStmt(),
             .Println => try self.parsePrintln(),
 
             // TODO make newlines tokens and consume newline?
@@ -437,6 +443,45 @@ pub const Parser = struct {
         };
     }
 
+    /// Copy of parseBlock for if branches
+    fn parseIfBranch(self: *@This()) !ast.IfBranch {
+        var branch = ast.IfBranch.init(self.allocator);
+        errdefer branch.deinit();
+
+        _ = try self.consumeSingle(.LeftBrace);
+
+        while (self.peek().ttype != .RightBrace) {
+            var stmt = try self.parseDecl();
+            ast.printNode(try self.mkStmt(stmt), 0);
+            try branch.append(stmt);
+        }
+
+        _ = try self.consumeSingle(.RightBrace);
+
+        return branch;
+    }
+
+    fn parseIfStmt(self: *@This()) !*Stmt {
+        _ = try self.consumeSingle(.If);
+        var condition = (try self.parseExpr()).Expr;
+
+        const then_branch = try self.parseIfBranch();
+
+        var else_branch: ?ast.IfBranch = null;
+
+        if (self.check(.Else)) {
+            _ = try self.consumeSingle(.Else);
+            else_branch = try self.parseIfBranch();
+        }
+
+        return try Stmt.mkIfStmt(
+            self.allocator,
+            condition,
+            then_branch,
+            else_branch,
+        );
+    }
+
     fn parsePrintln(self: *@This()) !*Stmt {
         _ = try self.consumeSingle(.Println);