From 67db992cf7fedc37adf6e8d177fbd4c0242f93d9 Mon Sep 17 00:00:00 2001
From: zhuyadong <lordix@gmail.com>
Date: Fri, 20 Sep 2024 22:37:57 +0800
Subject: [PATCH] fix bug when finding default method

---
 README.CN.md |  9 ++++-----
 README.md    |  9 ++++-----
 src/zoop.zig | 34 +++++++++++++++++++++++++++++-----
 3 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/README.CN.md b/README.CN.md
index b4c4098..249af5b 100644
--- a/README.CN.md
+++ b/README.CN.md
@@ -269,12 +269,11 @@ try t.expectEqualStrings(zoop.vcall(phuman, IName.getName, .{}), "override");
 `vcall`的性能说明：
 `vcall`会在能使用`cast`的情况下使用`cast`，否则使用`as`
 
-## 调试用接口 `zoop.IFormat`
-`zoop.IFormat`能方便通过 `std.fmt` 的 `format(...)`机制来输出对象的字符串形式内容。
+## 调试用接口 `IObject.formatAny`
+`zoop.IObject`能方便通过 `std.fmt` 的 `format(...)`机制来输出对象的字符串形式内容。
 ```zig
-// 定义一个实现 `zoop.IFormat`的类
+// 定义一个实现 `zoop.IObject.formatAny`的类
 pub const SomeClass = struct {
-    pub const extends = .{zoop.IFormat};
     name:[]const u8 align(zoop.alignment) = "some";
 
     pub fn formatAny(self: *SomeClass, writer: std.io.AnyWriter) anyerror!void {
@@ -284,6 +283,6 @@ pub const SomeClass = struct {
 
 // 下面代码就能输出 `SomeClass.formatAny` 的内容
 const psome = try zoop.new(t.allocator, SomeClass, null);
-std.debug.print("{}\n", .{zoop.cast(psome, zoop.IFormat)});
+std.debug.print("{}\n", .{zoop.cast(psome, zoop.IObject)});
 // output: SomeClass.name = some
 ```
\ No newline at end of file
diff --git a/README.md b/README.md
index 16784a0..38ba8b1 100644
--- a/README.md
+++ b/README.md
@@ -281,12 +281,11 @@ try t.expectEqualStrings(zoop.vcall(phuman, IName.getName, .{}), "override");
 Performance notes for `vcall`:
 `vcall` will use `cast` when possible, and `as` otherwise
 
-## Interface `zoop.IFormat` for print
-`zoop.IFormat` can conveniently output the string content of the object through the `format(...)` mechanism of `std.fmt`.
+## `zoop.IObject.formatAny` for print
+`zoop.IObject` can conveniently output the string content of the object through the `format(...)` mechanism of `std.fmt`.
 ```zig
-// define a class that implemented `zoop.IFormat`
+// define a class that implemented `zoop.IObject.formatAny`
 pub const SomeClass = struct {
-    pub const extends = .{zoop.IFormat};
     name:[]const u8 align(zoop.alignment) = "some";
 
     pub fn formatAny(self: *SomeClass, writer: std.io.AnyWriter) anyerror!void {
@@ -296,6 +295,6 @@ pub const SomeClass = struct {
 
 // print string from `SomeClass.formatAny` 
 const psome = try zoop.new(t.allocator, SomeClass, null);
-std.debug.print("{}\n", .{zoop.cast(psome, zoop.IFormat)});
+std.debug.print("{}\n", .{zoop.cast(psome, zoop.IObject)});
 // output: SomeClass.name = some
 ```
\ No newline at end of file
diff --git a/src/zoop.zig b/src/zoop.zig
index 500d955..7751e80 100644
--- a/src/zoop.zig
+++ b/src/zoop.zig
@@ -751,17 +751,41 @@ fn RealType(comptime T: type) type {
 
 fn DefaultMethodType(comptime T: type, comptime I: type, comptime name: []const u8) type {
     comptime {
-        if (@hasDecl(I, "Default")) {
-            const def = I.Default(T);
-            if (@hasDecl(def, name)) {
-                return @TypeOf(@field(def, name));
+        const ifaces = interfaces(I);
+        var all = tupleInit(.{});
+        for (ifaces.items) |iface| {
+            if (@hasDecl(iface, "Default")) {
+                const def = iface.Default(T);
+                if (@hasDecl(def, name)) {
+                    all = tupleAppend(all, iface);
+                }
             }
         }
+        switch (all.items.len) {
+            0 => {},
+            1 => return @TypeOf(@field(all.items[0].Default(T), name)),
+            else => @compileError(compfmt("multi default method '{s}' found in: {}", .{ name, all.items })),
+        }
 
         return void;
     }
 }
 
+fn defaultMethod(comptime T: type, comptime I: type, comptime name: []const u8) DefaultMethodType(T, I, name) {
+    comptime {
+        const ifaces = interfaces(I);
+        for (ifaces.items) |iface| {
+            if (@hasDecl(iface, "Default")) {
+                const def = iface.Default(T);
+                if (@hasDecl(def, name)) {
+                    return @field(def, name);
+                }
+            }
+        }
+        unreachable;
+    }
+}
+
 fn MethodType(comptime T: type, comptime name: []const u8) type {
     comptime {
         var Cur = if (isKlassType(T)) T.Class else T;
@@ -1091,7 +1115,7 @@ fn makeVtable(comptime T: type, comptime I: type) *anyopaque {
                         @field(val, field.name) = @ptrCast(&getMethod(T, field.name));
                     } else if (DefaultMethodType(T, I, field.name) != void) {
                         checkInterface(I);
-                        @field(val, field.name) = &@field(I.Default(T), field.name);
+                        @field(val, field.name) = @ptrCast(&defaultMethod(T, I, field.name));
                     } else {
                         @compileError(compfmt("{s} must implement method '{s}: {}'", .{ @typeName(T), field.name, field.type }));
                     }