○
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KORU100 false positive: string interpolation reference not counted as binding use inside for loop body (post-transform AST loses interpolation→binding association)
Failure Output
error[KORU010]: '_' is only legal as the body of a branch handler
--> tests/regression/200_COMPILER_FEATURES/220_FLOW_CHECKER/220_012_interpolation_use_in_for_loop/input.kz:26:0
|
26 | |> _
| ^
hint: '_' has meaning only as `| branch [binding] |> _`. Outside a branch handler body — top-level void chain, split-pipeline tail — `|> _` is meaningless.Code
// TEST: KORU100 false positive — binding used in string interpolation inside for loop
//
// BUG: The flow checker emits KORU100 (unused binding) for a binding that IS
// used inside {{ }} string interpolation, when the branch appears inside a
// for loop body.
//
// The same pattern compiles correctly at the top level of a flow (outside any
// for loop). The for transform rewrites the AST during the comptime pass, and
// the binding-use tracker appears to lose the interpolation→binding association
// in the post-transform AST.
//
// Discovered while building the @korulang/postgres library: the pattern
// | some name |> std/io:print.ln("row {{ i }}: {{ name:s }}")
// inside a for loop triggers KORU100 for 'name', despite it being used.
//
// Expected: Compiles successfully — 'val' IS used in {{ val:s }}
// Actual: error[KORU100]: unused binding 'val'
~import std/io
~import app/source
~for(0..3)
| each _ |> source:maybe-str()
| none |> std/io:print.ln("nothing")
| some val |> std/io:print.ln("got: {{ val:s }}")
|> _
Imported Files
// Helper module: an event that optionally returns a string.
// Used by 220_003 to trigger the for-loop binding-use bug.
~pub tor maybe-str {}
| some string
~proc maybe-str|zig {
return .{ .some = "hello" };
}