Mid rewrite

compiler/src/transform/closure.rs

@@ -0,0 +1,36 @@
+//! This module lowers closures by making implicit environment captures explicit
+//!
+//! Replace:
+//! ```js
+//! let x = 0;
+//! let y = true;
+//!
+//! function fn() {
+//!     f(x)
+//!     f(y)
+//! }
+//! ```
+//!
+//! With:
+//! ```js
+//! let x = 0;
+//! let y = true;
+//!
+//! function fn() {
+//!     f(fn.<var>.x);
+//!     f(fn.<var>.y);
+//! }
+//!
+//! fn.<var>.x = x; // by-ref
+//! fn.<var>.y = y; // by-ref
+//! ```
+//!
+//! i.e. captured fields are turned into fields on the function
+//!
+//! A special `define_field_ref` instr is introduced by `c_parse.py` to define a field on an
+//! object specifically by-reference. This signals to `escape.rs` to promote those values to
+//! the heap regardless if its a primitive or an object. This is required because normally
+//! primitives are only passed by-value, but closure captures must always be by-reference
+//!
+//! In the emitted C, every underlying "plain" function is called as:
+//! `fn(this, fields, arg_0, arg_1, ... arg_n)`