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Planned This feature is planned but not yet implemented.
OWED: unused branch binding `f` is KORU100; discard is `| opened _ |>`.
Failure Output
error[KORU010]: '_' is only legal as the body of a branch handler
--> tests/regression/200_COMPILER_FEATURES/220_FLOW_CHECKER/220_009_unused_binding_error/input.kz:13:0
|
13 | ~app/fs:open(path: "test.txt"): f |> _
| ^
hint: '_' has meaning only as `| branch [binding] |> _`. Outside a branch handler body — top-level void chain, split-pipeline tail — `|> _` is meaningless.Code
// TEST: KORU100 - Unused binding must be an error
// MUST_ERROR: 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"): f |> _
Supporting 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 tor open { path: string } -> *File<opened!>
~proc open|zig {
std.debug.print("Opening file\n", .{});
const f = std.heap.page_allocator.create(File) catch unreachable;
f.* = File{ .handle = 42 };
return f;
}
// Close - the ONLY consumer of <!opened>
~pub tor close { file: *File<!opened> }
~proc close|zig {
std.debug.print("Closing file (auto-discharged)\n", .{});
}
Actual compiler output
error[KORU010]: '_' is only legal as the body of a branch handler
--> tests/regression/200_COMPILER_FEATURES/220_FLOW_CHECKER/220_009_unused_binding_error/input.kz:13:0
|
13 | ~app/fs:open(path: "test.txt"): f |> _
| ^
hint: '_' has meaning only as `| branch [binding] |> _`. Outside a branch handler body — top-level void chain, split-pipeline tail — `|> _` is meaningless.Must fail at frontend compile:
Parsing or type-checking must reject the program.
Expected compiler error
error[KORU100]: unused binding 'f'
--> tests/regression/200_COMPILER_FEATURES/220_FLOW_CHECKER/220_009_unused_binding_error/input.kz:14:0
|
14 | | opened f |> _
| ^
hint: discard the binding using `_` if not needed
Test Configuration
MUST_ERROR