fix #17941: UnusedImport works for var/let/const/type invoked inside a generic (#17942)

* fix #17941: UnusedImport works for var/let/const/type invoked inside a generic

* fixup

compiler/semgnrc.nim

@@ -189,6 +189,9 @@ proc semGenericStmt(c: PContext, n: PNode,
   case n.kind
   of nkIdent, nkAccQuoted:
     result = lookup(c, n, flags, ctx)
+    if result != nil and result.kind == nkSym:
+      assert result.sym != nil
+      markUsed(c, n.info, result.sym)
   of nkDotExpr:
     #let luf = if withinMixin notin flags: {checkUndeclared} else: {}
     #var s = qualifiedLookUp(c, n, luf)

lib/pure/base64.nim

@@ -132,7 +132,7 @@ template encodeInternal(s, alphabet: typed): untyped =
   result.setLen(outputIndex)
 
 template encodeImpl() {.dirty.} =
-  when nimVM:
+  when nimvm:
     block:
       let lookupTableVM = if safe: cb64safeVM else: cb64VM
       encodeInternal(s, lookupTableVM)

lib/pure/collections/deques.nim

@@ -262,7 +262,7 @@ proc expandIfNeeded[T](deq: var Deque[T]) =
     var n = newSeq[T](cap * 2)
     var i = 0
     for x in mitems(deq):
-      when nimVM: n[i] = x # workaround for VM bug
+      when nimvm: n[i] = x # workaround for VM bug
       else: n[i] = move(x)
       inc i
     deq.data = move(n)

lib/system/platforms.nim

@@ -40,8 +40,7 @@ type
   OsPlatform* {.pure.} = enum ## the OS this program will run on.
     none, dos, windows, os2, linux, morphos, skyos, solaris,
     irix, netbsd, freebsd, openbsd, aix, palmos, qnx, amiga,
-    atari, netware, macos, macosx, haiku, android, js,
-    standalone, nintendoswitch
+    atari, netware, macos, macosx, haiku, android, js, standalone, nintendoswitch
 
 const
   targetOS* = when defined(windows): OsPlatform.windows