001 unused binding error

✓ Passing This code compiles and runs correctly.

Code

// TEST: KORU100 - Unused binding must be an error
// MUST_FAIL: unused binding 'f'
//
// When a user writes `| opened f |>` but never uses `f`, this is an error.
// The correct syntax for discarding is `| opened _ |>`.
//
// This test ensures the flow checker catches unused named bindings.
// The _ syntax is exempted from this check (explicit discard).

~import "$app/fs"

// ERROR: f is bound but never used - should trigger KORU100
~app.fs:open(path: "test.txt")
| opened f |> _

pub fn main() void {}

input.kz

Error Verification

Expected Error Pattern

error[KORU100]: unused binding

Actual Compiler Output ✓ Pattern matched

error[KORU100]: unused binding 'f'
  --> tests/regression/200_COMPILER_FEATURES/220_FLOW_CHECKER/220_001_unused_binding_error/input.kz:15:0
    |
 15 | | opened f |> _
    | ^
  hint: remove the binding if not needed

Imported Files

// Library module: fs
// Single disposal event - auto-discharge should work

const std = @import("std");

const File = struct { handle: i32 };

// Open a file - returns opened! state (requires cleanup)
~pub event open { path: []const u8 }
| opened { file: *File[opened!] }

~proc open {
    std.debug.print("Opening file\n", .{});
    const f = std.heap.page_allocator.create(File) catch unreachable;
    f.* = File{ .handle = 42 };
    return .{ .opened = .{ .file = f } };
}

// Close - the ONLY consumer of [!opened]
~pub event close { file: *File[!opened] }
| closed {}

~proc close {
    std.debug.print("Closing file (auto-discharged)\n", .{});
    return .{ .closed = .{} };
}

fs.kz

Test Configuration

MUST_FAIL

Expected Behavior:

FRONTEND_COMPILE_ERROR

← compiler flags declare 002 discard binding ok →