vize_l2 0.669.0

//! Canonical binding-surface rules consuming retained-expression constness.
//!
//! # The pessimal law's first real consumer
//!
//! [`constant_for_hoist`] is the first L2 pass code that *acts* on
//! P2-5b's const-classification contract: an
//! [`ExprRef::Opaque`](crate::expr::ExprRef::Opaque) is
//! **never** constant ([`OpaqueExpr::is_constant`], pessimal law 3 —
//! "no folding, hoisting, or caching may be justified by an opaque
//! expression"), and this pass is the first place where that answer
//! changes a published fact rather than a document. A retained-`None`
//! bind value therefore blocks its element's hoistability, exactly as
//! the law prescribes.
//!
//! # The JS rule (self-bound locals ported, free names still weaker)
//!
//! The backend-neutral retained-expression classifier now lives in
//! [`crate::analysis::constant_expression`]. For a retained
//! [`ExprRef::Js`](crate::expr::ExprRef::Js) the shipped classifier
//! (`vize_atelier_core::codegen::is_constant_simple_expression`, called
//! with `bindings: None` by `hoist_static/props.rs`) admits an
//! expression whose identifiers are locals it binds itself, allowlisted
//! globals, or helper aliases, and — a measured quirk — admits `this`.
//! The analysis stays off the `vize_croquis` allowlist. The rule here: a
//! retained expression is constant iff its walk meets
//!
//! - **every identifier reference is a local the expression binds**
//!   (an arrow or function parameter, or a binding declared in its
//!   body). Free names, including allowlisted globals, stay
//!   non-constant — strictly narrower than the shipped allowlist,
//! - **no `this`** (narrower than the shipped quirk),
//! - **no TS-only construct** (`as` / `satisfies` / `<T>` assertion /
//!   `!` non-null / explicit instantiation): the shipped classifier
//!   re-parses under an **mjs** source type and refuses these,
//! - and none of the shipped classifier's four literal context
//!   substrings (`_ctx.` and kin), mirrored byte-for-byte.
//!
//! Self-bound locals are the shipped answer, so `(v) => v.toFixed(2)`
//! hoists on both lanes (P3-17 `hoist_constant_gap`). One-sidedness
//! (`constant_for_hoist` ⇒ shipped-constant) still holds: every
//! remaining divergence is an L2 *under*-hoist, counted as
//! `consts_templates` instead of compared.
//!
//! [`OpaqueExpr::is_constant`]: crate::expr::OpaqueExpr::is_constant

use crate::op::{Attribute, BindingOp, DynamicName, SlotOp};
use vize_l0::camelize;

use super::constant_for_hoist;

/// Why one attached binding fails the legacy `is_hoistable_static_prop`
/// rule — `None` when it survives it. The `v-bind` shape gates are
/// mirrored (static name, modifiers within `camel`/`prop`/`attr`, the
/// prefixed key not `ref`/`class`), then the value goes through
/// [`constant_for_hoist`]; every non-`ui.bind` binding is unhoistable,
/// exactly as every non-`bind` legacy directive is.
///
/// The answer is `(op mnemonic, ui.bind rule)`: a non-`ui.bind` op is its
/// own blocker, and a `ui.bind` names the first gate it failed
/// (`dynamic-name`, `modifier`, `reserved-key`, `no-value`,
/// `non-constant`). The one implementation of the rule — the fact reads
/// its `is_none` through [`props_blocker`] — so a remark can never
/// explain a decision the analysis did not make.
#[must_use]
pub(super) fn binding_blocker(
    binding: &BindingOp<'_>,
) -> Option<(&'static str, Option<&'static str>)> {
    const fn bind_rule(rule: &'static str) -> Option<(&'static str, Option<&'static str>)> {
        Some(("ui.bind", Some(rule)))
    }
    let BindingOp::Bind(bind) = binding else {
        return Some((binding.mnemonic(), None));
    };
    let Some(DynamicName::Static(name)) = &bind.name else {
        return bind_rule("dynamic-name");
    };
    let mut has_camel = false;
    let mut has_prop = false;
    let mut has_attr = false;
    for modifier in bind.modifiers.iter() {
        match *modifier {
            "camel" => has_camel = true,
            "prop" => has_prop = true,
            "attr" => has_attr = true,
            _ => return bind_rule("modifier"),
        }
    }
    // The legacy precedence chain, mirrored: `camel` wins over `prop`
    // over `attr`, and the *prefixed* key is what the ref/class check
    // reads (`.ref` deliberately passes — the shipped quirk).
    let key = if has_camel {
        camelize(name)
    } else if has_prop {
        prefixed('.', name)
    } else if has_attr {
        prefixed('^', name)
    } else {
        vize_l0::ToCompactString::to_compact_string(name)
    };
    if matches!(key.as_str(), "ref" | "class") {
        return bind_rule("reserved-key");
    }
    let Some(value) = &bind.value else {
        return bind_rule("no-value");
    };
    if constant_for_hoist(value) {
        None
    } else {
        bind_rule("non-constant")
    }
}

fn prefixed(prefix: char, name: &str) -> vize_l0::String {
    let mut out = vize_l0::String::with_capacity(1 + name.len());
    out.push(prefix);
    out.push_str(name);
    out
}

/// `props_are_static_attrs` / the prop half of `has_static_props`:
/// every attribute except `ref`, every binding through the mirrored
/// `is_hoistable_static_prop` rule. Defined as [`props_blocker`]'s
/// `is_none`, so the remark and the fact share one rule.
#[must_use]
pub(super) fn props_all_hoistable(
    attributes: &[Attribute<'_>],
    bindings: &[BindingOp<'_>],
) -> bool {
    props_blocker(attributes, bindings).is_none()
}

/// The first thing failing [`props_all_hoistable`]: a `ref` attribute,
/// else the first unhoistable binding's [`binding_blocker`].
#[must_use]
pub(super) fn props_blocker(
    attributes: &[Attribute<'_>],
    bindings: &[BindingOp<'_>],
) -> Option<PropsBlocker> {
    if attributes.iter().any(|attribute| attribute.name == "ref") {
        return Some(PropsBlocker::RefAttribute);
    }
    bindings
        .iter()
        .find_map(binding_blocker)
        .map(|(op, rule)| PropsBlocker::Binding { op, rule })
}

/// Why a props surface is not hoistable.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(super) enum PropsBlocker {
    /// A static `ref` attribute.
    RefAttribute,
    /// A binding failing the hoist rule: its mnemonic, and for `ui.bind`
    /// the shape gate it failed.
    Binding {
        op: &'static str,
        rule: Option<&'static str>,
    },
}

/// The outlet's static-nested-child rule: its props surface (the
/// separated `name` position included) must be fully static.
#[must_use]
pub(super) fn slot_props_static(slot: &SlotOp<'_>) -> bool {
    let name_static = match &slot.name {
        DynamicName::Static(_) => true,
        DynamicName::Dynamic(expr) => constant_for_hoist(expr),
    };
    name_static && props_all_hoistable(&slot.attributes, &slot.bindings)
}