Highlight of ERROR STOP

Fixes #486

Author: gnikit

CHANGELOG.md

@@ -70,6 +70,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+- Fixed `error stop variable` syntax highlighting
+  ([#486](https://github.com/fortran-lang/vscode-fortran-support/issues/486))
 - Fixed issue with linter cache containing outdated folders
   ([#464](https://github.com/fortran-lang/vscode-fortran-support/issues/464))
 - Fixed slow performance of very long lines by using a different solution for

syntaxes/fortran_free-form.tmLanguage.json

@@ -2203,6 +2203,9 @@
         {
           "include": "#string-operators"
         },
+        {
+          "include": "#variable"
+        },
         {
           "include": "#invalid-character"
         }

test/resources/error-stop.f90

@@ -0,0 +1,4 @@
+error stop
+error stop 10
+error stop "val"//"10"
+error stop label

test/resources/error-stop.f90.snap

@@ -0,0 +1,21 @@
+>error stop
+#^^^^^^^^^^ source.fortran.free meta.statement.control.errorstop.fortran keyword.control.errorstop.fortran
+>error stop 10
+#^^^^^^^^^^ source.fortran.free meta.statement.control.errorstop.fortran keyword.control.errorstop.fortran
+#          ^ source.fortran.free meta.statement.control.errorstop.fortran
+#           ^^ source.fortran.free meta.statement.control.errorstop.fortran constant.numeric.fortran
+>error stop "val"//"10"
+#^^^^^^^^^^ source.fortran.free meta.statement.control.errorstop.fortran keyword.control.errorstop.fortran
+#          ^ source.fortran.free meta.statement.control.errorstop.fortran
+#           ^ source.fortran.free meta.statement.control.errorstop.fortran string.quoted.double.fortran punctuation.definition.string.begin.fortran
+#            ^^^ source.fortran.free meta.statement.control.errorstop.fortran string.quoted.double.fortran
+#               ^ source.fortran.free meta.statement.control.errorstop.fortran string.quoted.double.fortran punctuation.definition.string.end.fortran
+#                ^^ source.fortran.free meta.statement.control.errorstop.fortran keyword.other.concatination.fortran
+#                  ^ source.fortran.free meta.statement.control.errorstop.fortran string.quoted.double.fortran punctuation.definition.string.begin.fortran
+#                   ^^ source.fortran.free meta.statement.control.errorstop.fortran string.quoted.double.fortran
+#                     ^ source.fortran.free meta.statement.control.errorstop.fortran string.quoted.double.fortran punctuation.definition.string.end.fortran
+>error stop label
+#^^^^^^^^^^ source.fortran.free meta.statement.control.errorstop.fortran keyword.control.errorstop.fortran
+#          ^ source.fortran.free meta.statement.control.errorstop.fortran
+#           ^^^^^ source.fortran.free meta.statement.control.errorstop.fortran meta.parameter.fortran
+>