Add tests for parsing longident's with .

There are some identifiers that have the `.` character. We test cases
with +. and *.

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

test/base/test.ml

@@ -101,17 +101,36 @@ let _ = convert_longident "Base.( land )"
 
 let _ = convert_longident "A(B)"
 [%%expect{|
-Exception: Invalid_argument "Ppxlib.Longident.parse: \"A(B)\"".
+Exception: (Invalid_argument "Ppxlib.Longident.parse: \"A(B)\"")
 |}]
 
 let _ = convert_longident "A.B(C)"
 [%%expect{|
-Exception: Invalid_argument "Ppxlib.Longident.parse: \"A.B(C)\"".
+Exception: (Invalid_argument "Ppxlib.Longident.parse: \"A.B(C)\"")
 |}]
 
 let _ = convert_longident ")"
 [%%expect{|
-Exception: Invalid_argument "Ppxlib.Longident.parse: \")\"".
+Exception: (Invalid_argument "Ppxlib.Longident.parse: \")\"")
+|}]
+
+(* FIXME this is a bug *)
+let _ = convert_longident "+."
+[%%expect{|
+- : string * longident =
+("( + ).", Ppxlib.Longident.Ldot (Ppxlib.Longident.Lident "+", ""))
+|}]
+
+let _ = convert_longident "Foo.(+.)"
+[%%expect{|
+- : string * longident =
+("Foo.( +. )", Ppxlib.Longident.Ldot (Ppxlib.Longident.Lident "Foo", "+."))
+|}]
+
+let _ = convert_longident "Foo.( *. )"
+[%%expect{|
+- : string * longident =
+("Foo.( *. )", Ppxlib.Longident.Ldot (Ppxlib.Longident.Lident "Foo", "*."))
 |}]
 
 let _ = Ppxlib.Code_path.(file_path @@ top_level ~file_path:"dir/main.ml")