From 2eea1f201f4ff7829b8b17b192d3a2aeec7c9e9f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E3=83=AA=E3=82=AD=E8=90=8C?= <commits@liquidev.net>
Date: Tue, 2 Sep 2025 20:30:47 +0200
Subject: [PATCH] h2: add better VM value stack tracing

---
 crates/haku2/src/vm.zig | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/crates/haku2/src/vm.zig b/crates/haku2/src/vm.zig
index 910cb13..7bec9a1 100644
--- a/crates/haku2/src/vm.zig
+++ b/crates/haku2/src/vm.zig
@@ -147,6 +147,24 @@ pub fn stackFrame(vm: *const Vm, index: usize) StackFrame {
     }
 }
 
+const StackFmt = struct {
+    stack: []const Value,
+
+    pub fn format(f: *const StackFmt, writer: *std.Io.Writer) !void {
+        try writer.writeAll("[");
+        for (f.stack, 0..) |val, i| {
+            if (i != 0)
+                try writer.writeAll(", ");
+            try val.format(writer);
+        }
+        try writer.writeAll("]");
+    }
+};
+
+fn stackFmt(stack: []const Value) StackFmt {
+    return .{ .stack = stack };
+}
+
 /// Debug assertion for bytecode validity.
 /// In future versions, this may become disabled in release builds.
 fn validateBytecode(vm: *Vm, ok: bool, comptime fmt: []const u8, args: anytype) Error!void {
@@ -167,7 +185,7 @@ pub fn push(vm: *Vm, val: Value) Error!void {
     if (vm.stack_top >= vm.stack.len) {
         return vm.throw("too many live temporary values (local variables and expression operands)", .{});
     }
-    log.debug("PUSH {any} <- {f}", .{ vm.stack[0..vm.stack_top], val });
+    log.debug("PUSH {f} <- {f}", .{ stackFmt(vm.stack[0..vm.stack_top]), val });
     vm.stack[vm.stack_top] = val;
     vm.stack_top += 1;
 }
@@ -176,7 +194,7 @@ pub fn pop(vm: *Vm) Error!Value {
     try vm.validateBytecode(vm.stack_top > 0, "value stack underflow", .{});
     vm.stack_top -= 1;
     const result = vm.stack[vm.stack_top];
-    log.debug("POP  {any} -> {f}", .{ vm.stack[0..vm.stack_top], result });
+    log.debug("POP  {f} -> {f}", .{ stackFmt(vm.stack[0..vm.stack_top]), result });
     return vm.stack[vm.stack_top];
 }