ast: remove Expr Node (lives under Stmt)

src/ast.zig

@@ -14,7 +14,6 @@ pub const NodeType = enum {
     ConstDecl,
     Struct,
     Block,
-    Expr,
     Stmt,
 };
 
@@ -238,7 +237,6 @@ pub const Node = union(NodeType) {
 
     Block: StmtList,
 
-    Expr: *Expr,
     Stmt: *Stmt,
 
     pub fn mkRoot(allocator: *std.mem.Allocator) !*Node {

src/ast_printer.zig

@@ -70,12 +70,6 @@ pub fn printNode(node: *Node, ident: usize) void {
             }
         },
 
-        .Expr => |expr| {
-            printIdent(ident);
-            printExpr(expr);
-            std.debug.warn("\n");
-        },
-
         .Stmt => |stmt| {
             printIdent(ident);
             printStmt(ident, stmt);

src/parser.zig

@@ -162,12 +162,6 @@ pub const Parser = struct {
         return node;
     }
 
-    fn mkExpr(self: *Parser, expr: *Expr) !*ast.Node {
-        var node = try self.allocator.create(Node);
-        node.* = Node{ .Expr = expr };
-        return node;
-    }
-
     fn mkStmt(self: *Parser, stmt: *Stmt) !*ast.Node {
         var node = try self.allocator.create(Node);
         node.* = Node{ .Stmt = stmt };