fix(rtl): use const in more places

src/rtl/bst.zig

@@ -15,7 +15,7 @@ pub var nil: Node = .{
 
 /// Base struct for binary search trees.
 /// This should be used as a field in other types that are based on binary search trees, such as red-black trees or AVL trees.
-pub fn BST(comptime cmp: fn (*Node, *Node) std.math.Order) type {
+pub fn BST(comptime cmp: fn (*const Node, *const Node) std.math.Order) type {
     return struct {
         const Self = @This();
 
@@ -153,9 +153,9 @@ const MyNode = struct {
     value: u32,
 };
 
-fn node_cmp(a: *Node, b: *Node) std.math.Order {
-    const a_node: *MyNode = @fieldParentPtr("node", a);
-    const b_node: *MyNode = @fieldParentPtr("node", b);
+fn node_cmp(a: *const Node, b: *const Node) std.math.Order {
+    const a_node: *const MyNode = @fieldParentPtr("node", a);
+    const b_node: *const MyNode = @fieldParentPtr("node", b);
     if (a_node.value < b_node.value) return .lt;
     if (a_node.value > b_node.value) return .gt;
     return .eq;

src/rtl/rbtree.zig

@@ -14,7 +14,7 @@ fn set_color(node: *bst.Node, color: u2) void {
     node.parent.set_tag(color);
 }
 
-pub fn RBTree(comptime cmp: fn (*bst.Node, *bst.Node) std.math.Order) type {
+pub fn RBTree(comptime cmp: fn (*const bst.Node, *const bst.Node) std.math.Order) type {
     return struct {
         tree: bst.BST(cmp),
 
@@ -273,9 +273,9 @@ const TestNode = struct {
     value: i32,
 };
 
-fn cmp_test_node(a: *bst.Node, b: *bst.Node) std.math.Order {
-    const a_node: *TestNode = @fieldParentPtr("node", a);
-    const b_node: *TestNode = @fieldParentPtr("node", b);
+fn cmp_test_node(a: *const bst.Node, b: *const bst.Node) std.math.Order {
+    const a_node: *const TestNode = @fieldParentPtr("node", a);
+    const b_node: *const TestNode = @fieldParentPtr("node", b);
 
     if (a_node.value < b_node.value) return .lt;
     if (a_node.value > b_node.value) return .gt;

src/rtl/tagged_ptr.zig

@@ -13,7 +13,7 @@ pub fn TaggedPtr(comptime T: type) type {
         }
 
         /// Return the pointer with the tag bits masked out.
-        pub fn get_ptr(self: *Self) *T {
+        pub fn get_ptr(self: *const Self) *T {
             return @ptrFromInt(self.value & ~mask);
         }
 
@@ -23,7 +23,7 @@ pub fn TaggedPtr(comptime T: type) type {
         }
 
         /// Return the tag bits.
-        pub fn get_tag(self: *Self) u2 {
+        pub fn get_tag(self: *const Self) u2 {
             return @as(u2, @truncate(self.value & mask));
         }