fix #21896 asign parameter to global variable generates invalid code (#21900)

compiler/semstmts.nim

@@ -563,7 +563,7 @@ proc semVarMacroPragma(c: PContext, a: PNode, n: PNode): PNode =
         return result
 
 template isLocalSym(sym: PSym): bool =
-  sym.kind in {skVar, skLet} and not
+  sym.kind in {skVar, skLet, skParam} and not
     ({sfGlobal, sfPure} * sym.flags != {} or
       sfCompileTime in sym.flags) or
       sym.kind in {skProc, skFunc, skIterator} and

tests/global/t21896.nim

@@ -0,0 +1,9 @@
+discard """
+  errormsg: "cannot assign local to global variable"
+  line: 7
+"""
+
+proc example(a:int) =
+  let b {.global.} = a
+
+example(1)