Panic in RCA when using tuple variables as arguments to a lambda #2696
Description
The following should work but panics in RCA:
@EntryPoint(Base)
operation Main() : Unit {
// Works fine...
let x = (1, 2, 3);
Foo(x);
// Panics RCA!
let f : (Int, Int, Int) -> Unit = (a, b, c) -> {};
f(x)
}
function Foo(a : Int, b : Int, c : Int) : Unit {}The issue is in source/compiler/qsc_rca/src/core.rs inside of analyze_expr_call_with_spec_callee where it has special handling of lambdas with captures:
qsharp/source/compiler/qsc_rca/src/core.rs
Lines 460 to 479 in 3b1faf0
Because the lambda takes more than one argument, the results of
self.derive_arg_value_kinds is a vector representing the argument tuple, but the call to .chain with the preceeding iterator effectively unwraps it. We expect the parameter to be of type ((Int, Int, Int),) which is a tuple of single arity, but it gets passed as (Int, Int, Int) causing the panic.