keep param pragmas in typed proc AST (#24711)

fixes #24702

(cherry picked from commit 1f8da3835f)

compiler/semtypes.nim

@@ -1501,7 +1501,10 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
       addParamOrResult(c, arg, kind)
       styleCheckDef(c, a[j].info, arg)
       onDef(a[j].info, arg)
-      a[j] = newSymNode(arg)
+      if a[j].kind == nkPragmaExpr:
+        a[j][0] = newSymNode(arg)
+      else:
+        a[j] = newSymNode(arg)
 
   var r: PType = nil
   if n[0].kind != nkEmpty:

tests/pragmas/tparamcustompragma.nim

@@ -0,0 +1,16 @@
+discard """
+  nimout: '''
+proc foo(a {.attr.}: int) =
+  discard
+
+'''
+"""
+
+# fixes #24702
+
+import macros
+template attr*() {.pragma.}
+proc foo(a {.attr.}: int) = discard
+macro showImpl(a: typed) =
+  echo repr getImpl(a)
+showImpl(foo)