allow referencing other parameters in default parameter values

fix #7756
fix #1201
fix #7000
fix #3002
fix #1046

compiler/ast.nim

@@ -293,6 +293,10 @@ const
     # the compiler will avoid printing such names
     # in user messages.
 
+  sfHoisted* = sfForward
+    # an expression was hoised to an anonymous variable.
+    # the flag is applied to the var/let symbol
+
   sfNoForward* = sfRegister
     # forward declarations are not required (per module)
   sfReorder* = sfForward
@@ -455,6 +459,8 @@ type
     nfBlockArg  # this a stmtlist appearing in a call (e.g. a do block)
     nfFromTemplate # a top-level node returned from a template
     nfDefaultParam # an automatically inserter default parameter
+    nfDefaultRefsParam # a default param value references another parameter
+                       # the flag is applied to proc default values and to calls
 
   TNodeFlags* = set[TNodeFlag]
   TTypeFlag* = enum   # keep below 32 for efficiency reasons (now: beyond that)
@@ -972,7 +978,7 @@ const
   PersistentNodeFlags*: TNodeFlags = {nfBase2, nfBase8, nfBase16,
                                       nfDotSetter, nfDotField,
                                       nfIsRef, nfPreventCg, nfLL,
-                                      nfFromTemplate}
+                                      nfFromTemplate, nfDefaultRefsParam}
   namePos* = 0
   patternPos* = 1    # empty except for term rewriting macros
   genericParamsPos* = 2