Fix issue with inlining records in the presence of record coercion

Fixes #6253

Author: cristianoc

CHANGELOG.md

@@ -18,6 +18,9 @@
 #### :nail_care: Polish
 - Removed duplicate Super_error implementation in syntax https://github.com/rescript-lang/rescript-compiler/pull/6246
 
+#### :bug: Bug Fix
+- Fix issue with inlining records in the presence of record coercion https://github.com/rescript-lang/rescript-compiler/pull/6256
+
 # 11.0.0-alpha.6
 
 #### :boom: Breaking Change

jscomp/core/lam_util.ml

@@ -193,7 +193,18 @@ let field_flatten_get
       | SimpleForm l -> l
       | exception _ -> lam ()
     end
-  | Some (Constant (Const_block (_,_,ls))) -> 
+  | Some (Constant (Const_block (_, Blk_record {fields}, ls))) ->
+    (match info with
+      | Fld_record {name} ->
+        let found = ref None in
+        for i = 1 to Array.length fields - 1 do
+          if fields.(i) = name then found := Ext_list.nth_opt ls i done;
+        (match !found with
+        | Some c -> Lam.const c
+        | None  -> lam())
+      | _ -> lam ()
+    )
+  | Some (Constant (Const_block (_,_,ls))) ->
     begin match Ext_list.nth_opt ls i with 
       | None -> lam  ()
       | Some x -> Lam.const x

jscomp/test/RecordCoercion.js

@@ -15,3 +15,19 @@ let _ = (x: r3) => (x :> r4) // omit everything
 type nested1 = {n: r1, extra: int}
 type nested2 = {n: r2}
 let _ = (x: nested1) => (x :> nested2)
+
+module TestInlining = {
+  type a = {
+    number: int,
+    name: string,
+  }
+
+  type b = {name: string}
+
+  let a: a = {
+    number: 42,
+    name: "a",
+  }
+
+  let name = (a :> b).name
+}