Don't parse Int token with suffices as hash ident for poly variants (#408)

* Don't parse Int token with suffices as hash ident for poly variants

`#10s` should not be accepted as a numeric polyvariant identifier.

Fixes #407

* Tweak `variantIdent` error message based on feedback from bloodyowl

Co-authored-by: Matthias Le Brun <bloodyowl@icloud.com>

* Update hashIdent error tests

* Add printer test to verify that int tokens with suffix aren't printed as numeric polyvars

* Refine error message for numeric polyvars followed by a letter.

Co-authored-by: Matthias Le Brun <bloodyowl@icloud.com>

Author: IwanKaramazow

src/res_core.ml

@@ -77,7 +77,7 @@ Explanation: since records have a known, fixed shape, a spread like `{a, ...b}`
 Explanation: lists are singly-linked list, where a node contains a value and points to the next node. `list[a, ...bc]` efficiently creates a new item and links `bc` as its next nodes. `[...bc, a]` would be expensive, as it'd need to traverse `bc` and prepend each item to `a` one by one. We therefore disallow such syntax sugar.\n\
 Solution: directly use `concat`."
 
-  let variantIdent = "A polymorphic variant (e.g. #id) must start with an alphabetical letter."
+  let variantIdent = "A polymorphic variant (e.g. #id) must start with an alphabetical letter or be a number (e.g. #742)"
 
   let experimentalIfLet expr =
     let switchExpr = {expr with Parsetree.pexp_attributes = []} in
@@ -124,6 +124,9 @@ Solution: directly use `concat`."
 
   let sameTypeSpread =
     "You're using a ... spread without extra fields. This is the same type."
+
+  let polyVarIntWithSuffix number =
+    "A numeric polymorphic variant cannot be followed by a letter. Did you mean `#" ^ number ^ "`?"
 end
 
 
@@ -696,7 +699,12 @@ let parseHashIdent ~startPos p =
     Parser.next p;
     let text = if p.mode = ParseForTypeChecker then parseStringLiteral text else text in
     (text, mkLoc startPos p.prevEndPos)
-  | Int {i} ->
+  | Int {i; suffix} ->
+    let () = match suffix with
+    | Some _ ->
+      Parser.err p (Diagnostics.message (ErrorMessages.polyVarIntWithSuffix i))
+    | None -> ()
+    in
     Parser.next p;
     (i, mkLoc startPos p.prevEndPos)
   | _ ->
@@ -1202,7 +1210,12 @@ let rec parsePattern ?(alias=true) ?(or_=true) p =
         Parser.next p;
         let text = if p.mode = ParseForTypeChecker then parseStringLiteral text else text in
         (text, mkLoc startPos p.prevEndPos)
-      | Int {i} ->
+      | Int {i; suffix} ->
+        let () = match suffix with
+        | Some _ ->
+          Parser.err p (Diagnostics.message (ErrorMessages.polyVarIntWithSuffix i))
+        | None -> ()
+        in
         Parser.next p;
         (i, mkLoc startPos p.prevEndPos)
       | _ ->

tests/parsing/errors/other/expected/hashIdent.res.txt

@@ -0,0 +1,37 @@
+
+  Syntax error!
+  tests/parsing/errors/other/hashIdent.res:1:10-12
+
+  1 │ let x = #10s
+  2 │ 
+  3 │ type t = [ #red | #10s ] 
+
+  A numeric polymorphic variant cannot be followed by a letter. Did you mean `#10`?
+
+
+  Syntax error!
+  tests/parsing/errors/other/hashIdent.res:3:20-22
+
+  1 │ let x = #10s
+  2 │ 
+  3 │ type t = [ #red | #10s ] 
+  4 │ 
+  5 │ switch x {
+
+  A numeric polymorphic variant cannot be followed by a letter. Did you mean `#10`?
+
+
+  Syntax error!
+  tests/parsing/errors/other/hashIdent.res:6:4-6
+
+  4 │ 
+  5 │ switch x {
+  6 │ | #10s => ()
+  7 │ }
+  8 │ 
+
+  A numeric polymorphic variant cannot be followed by a letter. Did you mean `#10`?
+
+let x = `10
+type nonrec t = [ `red  | `10 ]
+;;match x with | `10 -> ()

tests/parsing/errors/other/hashIdent.res

@@ -0,0 +1,7 @@
+let x = #10s
+
+type t = [ #red | #10s ] 
+
+switch x {
+| #10s => ()
+}

tests/printer/typexpr/expected/variant.res.txt

@@ -112,3 +112,6 @@ type t = [
   | #1(string)
   | #2(int, string)
 ]
+
+// don't pick int with suffix as numeric polyvar
+type t = [#"10s" | #"20t"]

tests/printer/typexpr/variant.res

@@ -106,3 +106,6 @@ type t = [
   | #1(string)
   | #2(int, string)
 ]
+
+// don't pick int with suffix as numeric polyvar
+type t = [#"10s" | #"20t" ]