Bug: Generic channel functions (send, receive, close) fail type checking

[mjm918]

Description

The generic channel functions send<T>, receive<T>, and close<T> in std::threads fail type checking with confusing error messages. The typechecker is not properly resolving the generic type parameter T from the channel<T> type.

Error Messages

× type mismatch: expected int, found Spur(1) at 11:10
    ╭─[examples/channels.naml:11:10]
 10 │     println("Sending values...");
 11 │     send(ch, 10);
    ·          ─┬
    ·           ╰── expected int

The error "expected int, found Spur(1)" is confusing - Spur(1) appears to be an internal type representation leaking into user-facing error messages.

Reproduction

use std::threads::*;

fn main() {
    var ch: channel<int> = open_channel(5);
    send(ch, 10);        // Error: type mismatch
    var v: int = receive(ch);  // Error: type mismatch
    close(ch);           // Error: type mismatch
}

Expected Behavior

The generic functions should correctly infer T from the channel<T> argument:

• send<T>(ch: channel<T>, value: T) - should accept channel<int> and int
• receive<T>(ch: channel<T>) -> T - should return int for channel<int>
• close<T>(ch: channel<T>) - should accept channel<int>

Affected Files

• examples/channels.naml
• examples/spawn.naml

Technical Notes

The functions are defined as generic in namlc/src/typechecker/mod.rs:

StdModuleFn::generic("send", vec!["T"], vec![("ch", channel_t.clone()), ("value", Type::Generic("T".into()))], Type::Int),
StdModuleFn::generic("receive", vec!["T"], vec![("ch", channel_t.clone())], Type::Generic("T".into())),
StdModuleFn::generic("close", vec!["T"], vec![("ch", channel_t)], Type::Unit),

The issue appears to be in how generic type parameters are resolved when the first argument is a generic container type like channel<T>.

[mjm918]

Fixed by updating register_std_fn in namlc/src/typechecker/mod.rs.

The issue was that generic type parameters (Type::Generic with lasso::Spur::default()) were only being fixed for the return type inside Channel, but not for parameter types.

Added a recursive helper function fix_default_generic_spur that properly resolves default spurs in:

• Direct Type::Generic types
• Type::Channel(inner)
• Type::Array(inner)
• Type::Option(inner)
• Type::Map(k, v)

Now send(ch, 10), receive(ch), and close(ch) correctly type-check with channel<int> arguments.