Show errors and warnings for the 'smlnj' linter (#3957)

* Show errors and warnings for the 'smlnj' linter

Fixes #3953

* Change smlnj stdIn regex

autoload/ale/handlers/sml.vim

@@ -63,26 +63,35 @@ function! ale#handlers#sml#Handle(buffer, lines) abort
         let l:match2 = matchlist(l:line, l:pattern2)
 
         if len(l:match2) != 0
-            call add(l:out, {
+            if l:match2[1] =~# 'stdIn$'
-            \   'filename': l:match2[1],
+                let l:loc = {'bufnr': a:buffer}
+            else
+                let l:loc = {'filename': l:match2[1]}
+            endif
+
+            call add(l:out, extend(l:loc, {
             \   'lnum': l:match2[2] + 0,
             \   'col' : l:match2[3] - 1,
             \   'text': l:match2[4],
             \   'type': l:match2[4] =~# '^Warning' ? 'W' : 'E',
-            \})
+            \}))
-
             continue
         endif
 
         let l:match = matchlist(l:line, l:pattern)
 
         if len(l:match) != 0
-            call add(l:out, {
+            if l:match[1] =~# 'stdIn$'
-            \   'filename': l:match[1],
+                let l:loc = {'bufnr': a:buffer}
+            else
+                let l:loc = {'filename': l:match[1]}
+            endif
+
+            call add(l:out, extend(l:loc, {
             \   'lnum': l:match[2] + 0,
             \   'text': l:match[3] . ': ' . l:match[4],
             \   'type': l:match[3] is# 'error' ? 'E' : 'W',
-            \})
+            \}))
             continue
         endif
     endfor

test/handler/test_sml_handler.vader

@@ -85,3 +85,35 @@ Execute (Testing a warning):
   \ "val f = fn : int -> int",
   \ "-",
   \])
+
+Execute (Testing stdIn):
+  AssertEqual [
+  \ {
+  \   'bufnr': 42,
+  \   'lnum': 1,
+  \   'col': 5,
+  \   'type': 'E',
+  \   'text': "Error: operator and operand don't agree [overload conflict]",
+  \ },
+  \ {
+  \   'bufnr': 42,
+  \   'lnum': 2,
+  \   'col': 4,
+  \   'type': 'E',
+  \   'text': "Error: operator and operand don't agree [overload conflict]",
+  \ },
+  \],
+  \ ale#handlers#sml#Handle(42, [
+  \ "Standard ML of New Jersey v110.79 [built: Sat Oct 26 12:27:04 2019]",
+  \ "- = stdIn:1.6-1.21 Error: operator and operand don't agree [overload conflict]",
+  \ "  operator domain: [+ ty] * [+ ty]",
+  \ "  operand:         string * [int ty]",
+  \ "  in expression:",
+  \ '    "abc" + 123',
+  \ "stdIn:2.5-2.20 Error: operator and operand don't agree [overload conflict]",
+  \ "  operator domain: [+ ty] * [+ ty]",
+  \ "  operand:         [+ ty] * string",
+  \ "  in expression:",
+  \ '    890 + "xyz"',
+  \ "-",
+  \])