Fix precedence of stack_ keyword (#92)

the two main bugs in the PR description, plus some expressions nobody
should write, but might write anyway

lib/Ast.ml

@@ -2464,10 +2464,15 @@ end = struct
             ( Pexp_apply _ | Pexp_fun _ | Pexp_function _ | Pexp_lazy _
             | Pexp_new _ | Pexp_tuple _
             | Pexp_construct (_, Some _)
+            | Pexp_cons _ | Pexp_infix _ | Pexp_prefix _ | Pexp_stack _
+            | Pexp_let _ | Pexp_letop _ | Pexp_letopen _ | Pexp_letmodule _
+            | Pexp_send _ | Pexp_setfield _ | Pexp_ifthenelse _
             | Pexp_variant (_, Some _) )
         ; _ } ) ->
         true
-    | Exp {pexp_desc= Pexp_apply _; _}, {pexp_desc= Pexp_stack _; _} -> true
+    | ( Exp {pexp_desc= Pexp_apply _ | Pexp_construct _; _}
+      , {pexp_desc= Pexp_stack _; _} ) ->
+        true
     | ( Str
           { pstr_desc=
               Pstr_value

test/passing/tests/stack-erased.ml.js-ref

@@ -110,3 +110,30 @@ let x =
          (* 12 *)
          (Foo x)) )
 ;;
+
+(* Constructor precedence *)
+
+let x = Foo (stack_ ((), ()))
+let x = stack_ (() :: [])
+
+(* Tuples *)
+
+let x = stack_ (1, 2)
+let x = stack_ #(1, 2)
+let x = stack_ (~x:1, ~y:2)
+
+(* Expressions rejected by the typechecker *)
+
+let x = stack_ (x + y)
+let x = stack_ (-x)
+let x = stack_ (stack_ (Foo x))
+
+let x =
+  stack_
+    (let y = 1 in
+     Some y)
+;;
+
+let x = stack_ (c#x)
+let x = stack_ (r.x <- x)
+let x = stack_ (if x then y else z)

test/passing/tests/stack-erased.ml.ref

@@ -113,3 +113,35 @@ let x =
       (* 12 *)
         Foo
         x ) )
+
+(* Constructor precedence *)
+
+let x = Foo ((), ())
+
+let x = () :: []
+
+(* Tuples *)
+
+let x = (1, 2)
+
+let x = #(1, 2)
+
+let x = (~x:1, ~y:2)
+
+(* Expressions rejected by the typechecker *)
+
+let x = x + y
+
+let x = -x
+
+let x = Foo x
+
+let x =
+  let y = 1 in
+  Some y
+
+let x = c#x
+
+let x = r.x <- x
+
+let x = if x then y else z

test/passing/tests/stack.ml

@@ -95,3 +95,37 @@ let x = stack_ (stack_ ( 2 , stack_ "hello" ),  ~x:(stack_ (Foo x)))
 
 let x = (* 1 *) stack_ (* 2 *) ((* 3 *) stack_ (* 4 *) ((* 5 *) 1 (* 6 *),
         stack_ (* 7 *) "hello" (* 8 *)) (* 9 *), (* 10 *) ~x:((* 11 *)stack_ (* 12 *) (Foo x)))
+
+(* Constructor precedence *)
+
+let x = Foo (stack_ ((), ()))
+
+let x = stack_ (() :: [])
+
+(* Tuples *)
+
+let x = stack_ (1, 2)
+
+let x = stack_ #(1, 2)
+
+let x = stack_ (~x:1, ~y:2)
+
+(* Expressions rejected by the typechecker *)
+
+let x = stack_ (x + y)
+
+let x = stack_ (-x)
+
+let x = stack_ (stack_ (Foo x))
+
+let x = stack_ (let y = 1 in Some y)
+
+let x = stack_ (c # x)
+
+let x = stack_ (r.x <- x)
+
+let x = stack_ (
+  if x
+  then y
+  else z
+)

test/passing/tests/stack.ml.js-ref

@@ -110,3 +110,30 @@ let x =
          (* 12 *)
          (Foo x)) )
 ;;
+
+(* Constructor precedence *)
+
+let x = Foo (stack_ ((), ()))
+let x = stack_ (() :: [])
+
+(* Tuples *)
+
+let x = stack_ (1, 2)
+let x = stack_ #(1, 2)
+let x = stack_ (~x:1, ~y:2)
+
+(* Expressions rejected by the typechecker *)
+
+let x = stack_ (x + y)
+let x = stack_ (-x)
+let x = stack_ (stack_ (Foo x))
+
+let x =
+  stack_
+    (let y = 1 in
+     Some y)
+;;
+
+let x = stack_ (c#x)
+let x = stack_ (r.x <- x)
+let x = stack_ (if x then y else z)

test/passing/tests/stack.ml.ref

@@ -117,3 +117,36 @@ let x =
          (* 11 *)
          (* 12 *)
          (Foo x ) ) )
+
+(* Constructor precedence *)
+
+let x = Foo (stack_ ((), ()))
+
+let x = stack_ (() :: [])
+
+(* Tuples *)
+
+let x = stack_ (1, 2)
+
+let x = stack_ #(1, 2)
+
+let x = stack_ (~x:1, ~y:2)
+
+(* Expressions rejected by the typechecker *)
+
+let x = stack_ (x + y)
+
+let x = stack_ (-x)
+
+let x = stack_ (stack_ (Foo x))
+
+let x =
+  stack_
+    (let y = 1 in
+     Some y )
+
+let x = stack_ (c#x)
+
+let x = stack_ (r.x <- x)
+
+let x = stack_ (if x then y else z)