From b8fec06fa26ec5ddd2b1b9cb5099de3a9df9109f Mon Sep 17 00:00:00 2001
From: Meghan Denny <hello@nektro.net>
Date: Thu, 13 Feb 2025 12:31:47 -0800
Subject: [PATCH] add hasFn

---
 src/hasFn.zig | 25 +++++++++++++++++++++++++
 src/lib.zig   |  1 +
 2 files changed, 26 insertions(+)
 create mode 100644 src/hasFn.zig

diff --git a/src/hasFn.zig b/src/hasFn.zig
new file mode 100644
index 0000000000000000000000000000000000000000..1e583d1bc98ef76c09abe6e58267932b58ef5db3
--- /dev/null
+++ b/src/hasFn.zig
@@ -0,0 +1,25 @@
+const std = @import("std");
+const string = []const u8;
+const extras = @import("./lib.zig");
+
+pub fn hasFn(comptime name: []const u8) fn (type) bool {
+    const Closure = struct {
+        pub fn trait(comptime T: type) bool {
+            if (!comptime extras.isContainer(T)) return false;
+            if (!comptime @hasDecl(T, name)) return false;
+            const DeclType = @TypeOf(@field(T, name));
+            return @typeInfo(DeclType) == .Fn;
+        }
+    };
+    return Closure.trait;
+}
+
+test {
+    const TestStruct = struct {
+        pub fn useless() void {}
+    };
+
+    try std.testing.expect(hasFn("useless")(TestStruct));
+    try std.testing.expect(!hasFn("append")(TestStruct));
+    try std.testing.expect(!hasFn("useless")(u8));
+}
diff --git a/src/lib.zig b/src/lib.zig
index 3e34729afb6ade7b2e0e2c4c10245bc3eede9f8a..c6cc79d2ae4dcba59c3060cb722ba2c46dcf4da1 100644
--- a/src/lib.zig
+++ b/src/lib.zig
@@ -103,3 +103,4 @@ pub usingnamespace @import("./indexOfSlice.zig");
 pub usingnamespace @import("./mapBy.zig");
 pub usingnamespace @import("./lessThanBy.zig");
 pub usingnamespace @import("./isContainer.zig");
+pub usingnamespace @import("./hasFn.zig");
-- 
2.54.0