Math.tan/asin/acos/atan/atan2 return their input unchanged (silently wrong)

[proggeramlug]

Summary

The codegen arms for Math.tan, Math.asin, Math.acos, Math.atan, and Math.atan2 lower to return the argument unchanged. Programs calling these get a silent identity function with zero diagnostic.

Math.sin / Math.cos are correctly wired to llvm.sin.f64 / llvm.cos.f64 intrinsics — the bug is specific to the five trig functions above.

Evidence

crates/perry-codegen/src/expr.rs:5389-5397:

// tan/asin/acos/atan: still stubs returning input (runtime has no wrappers yet, no LLVM intrinsics for these).
Expr::MathTan(o)
| Expr::MathAsin(o)
| Expr::MathAcos(o)
| Expr::MathAtan(o) => lower_expr(ctx, o),
Expr::MathAtan2(y, x) => {
    let _ = lower_expr(ctx, y)?;
    lower_expr(ctx, x)
}

The real implementations already exist in crates/perry-runtime/src/math.rs:46-62 (js_math_tan, js_math_asin, js_math_acos, js_math_atan, js_math_atan2, each calling f64::tan() etc.), but nothing calls them.

Impact

• Math.tan(x) === x for any x
• Math.atan2(y, x) === x (y is evaluated and discarded)
• No warning, no error — the program compiles and runs with wrong numbers
• Any graphics / geometry / physics code relying on these is silently incorrect

Suggested fix

Wire the existing runtime functions through codegen the same way other Math.* helpers are called (extern decl in runtime_decls.rs + a ctx.block().call(DOUBLE, "js_math_tan", &[arg]) in the codegen arm). Or, where applicable, use llvm.* intrinsics — LLVM has no tan/asin/acos/atan intrinsics on all targets, so runtime calls are the safer path.

Reproducer

console.log(Math.tan(0));    // expected 0, got 0 (lucky)
console.log(Math.tan(1));    // expected ~1.557, got 1
console.log(Math.atan2(1,1)); // expected ~0.785, got 1

[proggeramlug]

Fixed in 69ca00c on branch fix/issue-142-math-trig (v0.5.165). Wired the five codegen arms at crates/perry-codegen/src/expr.rs:5417-5424 to the existing js_math_tan/asin/acos/atan/atan2 runtime functions. Verified against node --experimental-strip-types: Math.tan(1) = 1.557… (was 1), Math.atan2(0,-1) = π (was -1).