Require whitespace before as in to/downto labels (#1085)

* Require whitespace before `as` in `to`/`downto` labels

The `RE_TO_DOWNTO_AS_LABELS` rule previously used `\s*` between `(to|downto)` and `(as)`,
allowing zero spaces and accidentally matching identifiers like "toast".

Change the pattern to `\s+` so that an actual space is required, preventing spurious `as`
highlighting inside identifiers.

* Prefix `RE_TO_DOWNTO_AS_LABELS` patterns with `~` to ensure they only apply to labelled arguments

* Add CHANGELOG entry

Author: mediremi

CHANGELOG.md

@@ -14,6 +14,8 @@
 
 #### :bug: Bug fix
 
+- Fix: incorrect highlighting of `as` inside labelled arguments like `toast` https://github.com/rescript-lang/rescript-vscode/pull/1085
+
 - Fix: bug where incremental analysis does not work when the project folder contains a dot. https://github.com/rescript-lang/rescript-vscode/pull/1080
 
 - Fix: bug where incremental compilation crashes when rewatch is being run in a specific package vs the root of the monorepo. https://github.com/rescript-lang/rescript-vscode/pull/1082

grammars/rescript.tmLanguage.json

@@ -10,7 +10,7 @@
     "RE_TO_DOWNTO_AS_LABELS": {
       "patterns": [
         {
-          "match": "(to|downto)\\s*(=)",
+          "match": "~(to|downto)\\s*(=)",
           "captures": {
             "1": {
               "name": "variable"
@@ -21,7 +21,7 @@
           }
         },
         {
-          "match": "(to|downto)\\s*(as)",
+          "match": "~(to|downto)\\s+(as)",
           "captures": {
             "1": {
               "name": "variable"