Treat uncurried application of primitives like curried application

Primitives are treated specially in the type checker, so that when fully applied, no function is generated.
With uncurried application, primitives are wrapped with eta expansion before being used, because the encoding via `Js.Internal.opaqueFullApply` disables the special treatment by the type checker.
This PR treats uncurried application of primitives like curried application, to help `Lam` compilation produce better code instead of leaving eta-expanded functions in the output.

Author: cristianoc

CHANGELOG.md

@@ -54,6 +54,7 @@ These are only breaking changes for unformatted code.
 - Remove method application via operator `##`, which does not exist in `.res` syntax https://github.com/rescript-lang/rescript-compiler/pull/5844
 - Treat `@meth` annotation as making the type uncurried for backwards compatibitly with some examples https://github.com/rescript-lang/rescript-compiler/pull/5845
 - Process `@set` annotation for field update as generating an uncurried function https://github.com/rescript-lang/rescript-compiler/pull/5846
+- Treat uncurried application of primitives like curried application, which produces better output https://github.com/rescript-lang/rescript-compiler/pull/5851
 
 # 10.1.0-rc.6
 

jscomp/ml/typecore.ml

@@ -2041,7 +2041,11 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
           exp_attributes = sexp.pexp_attributes;
           exp_env = env } in
 
-      if fully_applied then
+      let is_primitive = match funct.exp_desc with
+        | Texp_ident (_, _, {val_kind = Val_prim _}) -> true
+        | _ -> false in
+
+      if fully_applied && not is_primitive then
         rue (apply_internal "opaqueFullApply" (mk_apply (apply_internal "opaque" funct) args))
       else
         rue (mk_apply funct args)

jscomp/test/UncurriedExternals.js

@@ -26,11 +26,9 @@ function tg(arr) {
 
 var tc = Object.assign({}, "abc");
 
-var te = (function (prim) {
-      return prim;
-    })({
-      RE_EXN_ID: "Not_found"
-    });
+var te = {
+  RE_EXN_ID: "Not_found"
+};
 
 var tcr = {};
 
@@ -87,11 +85,9 @@ function tg$1(arr) {
 
 var tc$1 = Object.assign({}, "abc");
 
-var te$1 = (function (prim) {
-      return prim;
-    })({
-      RE_EXN_ID: "Not_found"
-    });
+var te$1 = {
+  RE_EXN_ID: "Not_found"
+};
 
 var tcr$1 = {};
 

jscomp/test/bs_splice_partial.js

@@ -32,7 +32,7 @@ function test_cb(x) {
 }
 
 function f(x) {
-  v(x);
+  Curry._1(v, x);
 }
 
 function testUndefined(param) {

lib/4.06.1/unstable/js_compiler.ml

@@ -42771,7 +42771,11 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
           exp_attributes = sexp.pexp_attributes;
           exp_env = env } in
 
-      if fully_applied then
+      let is_primitive = match funct.exp_desc with
+        | Texp_ident (_, _, {val_kind = Val_prim _}) -> true
+        | _ -> false in
+
+      if fully_applied && not is_primitive then
         rue (apply_internal "opaqueFullApply" (mk_apply (apply_internal "opaque" funct) args))
       else
         rue (mk_apply funct args)

lib/4.06.1/unstable/js_playground_compiler.ml

@@ -42771,7 +42771,11 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
           exp_attributes = sexp.pexp_attributes;
           exp_env = env } in
 
-      if fully_applied then
+      let is_primitive = match funct.exp_desc with
+        | Texp_ident (_, _, {val_kind = Val_prim _}) -> true
+        | _ -> false in
+
+      if fully_applied && not is_primitive then
         rue (apply_internal "opaqueFullApply" (mk_apply (apply_internal "opaque" funct) args))
       else
         rue (mk_apply funct args)

lib/4.06.1/whole_compiler.ml

@@ -97765,7 +97765,11 @@ and type_expect_ ?in_function ?(recarg=Rejected) env sexp ty_expected =
           exp_attributes = sexp.pexp_attributes;
           exp_env = env } in
 
-      if fully_applied then
+      let is_primitive = match funct.exp_desc with
+        | Texp_ident (_, _, {val_kind = Val_prim _}) -> true
+        | _ -> false in
+
+      if fully_applied && not is_primitive then
         rue (apply_internal "opaqueFullApply" (mk_apply (apply_internal "opaque" funct) args))
       else
         rue (mk_apply funct args)