Fix nimsuggest highlight for import statements (#23263)

Currently, I don't have syntax highlighting (+ no/wrong
jump-to-definition) for some import statement forms, namely:

- `import module/name/with/(slashes)`
- `import (mod) as alias`
- `import basemod/[ (sub1), (sub2) ]`

With this patch, highlight/def will work for the regions indicated by
parentheses.

(cherry picked from commit 15577043e8)

compiler/importer.nim

@@ -304,7 +304,15 @@ proc myImportModule(c: PContext, n: var PNode, importStmtResult: PNode): PSym =
       var prefix = ""
       if realModule.constraint != nil: prefix = realModule.constraint.strVal & "; "
       message(c.config, n.info, warnDeprecated, prefix & realModule.name.s & " is deprecated")
-    suggestSym(c.graph, n.info, result, c.graph.usageSym, false)
+
+    proc suggestMod(n: PNode; s: PSym) =
+      if n.kind == nkImportAs:
+        suggestMod(n[0], realModule)
+      elif n.kind == nkInfix:
+        suggestMod(n[2], s)
+      else:
+        suggestSym(c.graph, n.info, s, c.graph.usageSym, false)
+    suggestMod(n, result)
     importStmtResult.add newSymNode(result, n.info)
     #newStrNode(toFullPath(c.config, f), n.info)
 

nimsuggest/tests/timport_highlight.nim

@@ -0,0 +1,12 @@
+import std/paths
+import json as J
+import std/[os,streams]#[!]#
+
+discard """
+$nimsuggest --tester $file
+>highlight $1
+highlight;;skModule;;1;;11;;5
+highlight;;skModule;;2;;7;;4
+highlight;;skModule;;3;;12;;2
+highlight;;skModule;;3;;15;;7
+"""