add if statements

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

@@ -88,12 +88,12 @@ pub const Expr = union(ExprType) {
     Grouping: *Expr,
 };
 
-pub const IfBranch = std.ArrayList(Stmt);
+pub const IfBranch = std.ArrayList(*Stmt);
 
 pub const IfStmt = struct {
     condition: *Expr,
     then_branch: IfBranch,
-    else_branch: IfBranch,
+    else_branch: ?IfBranch,
 };
 
 pub const Stmt = union(enum) {
@@ -107,6 +107,23 @@ pub const Stmt = union(enum) {
         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) {
@@ -138,6 +155,22 @@ 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| {
@@ -147,15 +180,8 @@ pub fn printNode(node: *Node, ident: usize) void {
                 std.debug.warn("({} {}) ", param.name.lexeme, param.typ.lexeme);
             }
 
-            std.debug.warn(") (\n");
+            printBlock(ident + 1, decl.body, false);
-
+            std.debug.warn(")\n");
-            for (decl.body.toSlice()) |stmt| {
-                printIdent(ident + 1);
-                printStmt(stmt);
-                std.debug.warn("\n");
-            }
-
-            print(ident, ")\n");
         },
 
         .ConstDecl => |consts| {
@@ -189,7 +215,7 @@ pub fn printNode(node: *Node, ident: usize) void {
 
         .Stmt => |stmt| blk: {
             printIdent(ident);
-            printStmt(stmt);
+            printStmt(ident, stmt);
             std.debug.warn("\n");
         },
 
@@ -250,10 +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

@@ -419,7 +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);
@@ -436,6 +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?
@@ -443,6 +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);