[highlights] Add TSSymbol highlight group

Addresses issue #892

Ruby and Dart literal symbols will now be highlighted by the new
TSSymbol highlight group, which itself will, by default, link to the Vim
Identifier highlight group. Vim theme authors can then set their
TSSymbol colors.

Symbol highlighting can apply to a number of languages as noted in the
following Wikipedia page: https://en.wikipedia.org/wiki/Symbol_(programming)

Not just for Ruby and Dart.

6 files changed, 10 insertions, 2 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e671b24da..1fbbb8bd4 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -143,6 +143,7 @@ effect on highlighting. We will work on improving highlighting in the near futur
 @type
 @type.builtin
 @namespace for identifiers referring to namespaces
+@symbol for identifiers referring to symbols
 @attribute for e.g. Python decorators
 ```
 
diff --git a/doc/nvim-treesitter.txt b/doc/nvim-treesitter.txt
index eb1573ef0..6ad57eef9 100644
--- a/doc/nvim-treesitter.txt
+++ b/doc/nvim-treesitter.txt
@@ -560,6 +560,10 @@ For regexes.
                                                            *hl-TSStringEscape*
 For escape characters within a string.
 
+`TSSymbol`
+                                                                 *hl-TSSymbol*
+For identifiers referring to symbols or atoms.
+
 `TSTag`
                                                                    *hl-TSTag*
 Tags like html tag names.
diff --git a/lua/nvim-treesitter/highlight.lua b/lua/nvim-treesitter/highlight.lua
index 753aeed7b..a0c6ee61b 100644
--- a/lua/nvim-treesitter/highlight.lua
+++ b/lua/nvim-treesitter/highlight.lua
@@ -71,6 +71,8 @@ hlmap["string"] = "TSString"
 hlmap["string.regex"] = "TSStringRegex"
 hlmap["string.escape"] = "TSStringEscape"
 
+hlmap["symbol"] = "TSSymbol"
+
 hlmap["tag"] = "TSTag"
 hlmap["tag.delimiter"] = "TSTagDelimiter"
 
diff --git a/plugin/nvim-treesitter.vim b/plugin/nvim-treesitter.vim
index 0bc3ae8d6..571f2945e 100644
--- a/plugin/nvim-treesitter.vim
+++ b/plugin/nvim-treesitter.vim
@@ -54,6 +54,7 @@ highlight default link TSConstructor Special
 highlight default link TSAnnotation PreProc
 highlight default link TSAttribute PreProc
 highlight default link TSNamespace Include
+highlight default link TSSymbol Identifier
 
 highlight default link TSConditional Conditional
 highlight default link TSRepeat Repeat
diff --git a/queries/dart/highlights.scm b/queries/dart/highlights.scm
index 9080f3f40..65c5d6e2d 100644
--- a/queries/dart/highlights.scm
+++ b/queries/dart/highlights.scm
@@ -144,7 +144,7 @@
     ; (hex_floating_point_literal)
 ] @number
 
-(symbol_literal) @string.special
+(symbol_literal) @symbol
 (string_literal) @string
 (true) @boolean
 (false) @boolean
diff --git a/queries/ruby/highlights.scm b/queries/ruby/highlights.scm
index e77687920..3437605c1 100644
--- a/queries/ruby/highlights.scm
+++ b/queries/ruby/highlights.scm
@@ -144,7 +144,7 @@
  (simple_symbol)
  (delimited_symbol)
  (hash_key_symbol)
- ] @property
+ ] @symbol
 
 (pair key: (hash_key_symbol) ":" @constant)
 (regex) @string.regex