fix: allow overriding custom true / false constructors

Changes.md

@@ -11,6 +11,8 @@ Unreleased
   ([#1147](https://github.com/melange-re/melange/pull/1147))
 - Add support for dynamic `import()`
   ([#1164](https://github.com/melange-re/melange/pull/1164))
+- Fix code generation of custom `true` / `false` constructors
+  ([#1175](https://github.com/melange-re/melange/pull/1175))
 
 4.0.1 2024-06-07
 ---------------

test/blackbox-tests/custom-predef.t

@@ -0,0 +1,29 @@
+Demonstrate redefining the `true` / `false` constructors
+
+  $ . ./setup.sh
+  $ cat > x.ml <<EOF
+  > type t = A | true | false
+  > let z : t = A
+  > let x : t = true
+  > let y : t = false
+  > let t : bool = false
+  > EOF
+
+  $ melc -ppx melppx x.ml
+  // Generated by Melange
+  'use strict';
+
+
+  const z = /* A */0;
+
+  const x = /* true */1;
+
+  const y = /* false */2;
+
+  const t = false;
+
+  exports.z = z;
+  exports.x = x;
+  exports.y = y;
+  exports.t = t;
+  /* No side effect */