Fix getTypeImpl not returning defaults (#25592)

`getTypeImpl` and friends were always putting `nkEmpty` in the default
value field which meant the default values couldn't be introspected.
This copies the default AST so it can be seen in the returned object

(cherry picked from commit edbb32e4c4)

compiler/vmdeps.nim

@@ -62,7 +62,10 @@ proc objectNode(cache: IdentCache; n: PNode; idgen: IdGenerator): PNode =
     result = newNodeI(nkIdentDefs, n.info)
     result.add n  # name
     result.add mapTypeToAstX(cache, n.sym.typ, n.info, idgen, true, false)  # type
-    result.add newNodeI(nkEmpty, n.info)  # no assigned value
+    if n.sym.ast != nil:
+      result.add copyTree(n.sym.ast)
+    else:
+      result.add newNodeI(nkEmpty, n.info)  # no assigned value
   else:
     result = copyNode(n)
     for i in 0..<n.safeLen:
@@ -87,7 +90,10 @@ proc mapTypeToAstX(cache: IdentCache; t: PType; info: TLineInfo;
     var id = newNodeX(nkIdentDefs)
     id.add n  # name
     id.add mapTypeToAst(t, info)  # type
-    id.add newNodeI(nkEmpty, info)  # no assigned value
+    if n.sym.ast != nil:
+      id.add copyTree(n.sym.ast)
+    else:
+      id.add newNodeI(nkEmpty, n.info)  # no assigned value
     id
   template newIdentDefs(s): untyped = newIdentDefs(s, s.typ)
 

tests/macros/tgettypeimpl_defaults.nim

@@ -0,0 +1,39 @@
+discard """
+nimout: '''
+ObjectTy
+  Empty
+  Empty
+  RecList
+    IdentDefs
+      Sym "noDefault"
+      Sym "int"
+      Empty
+    IdentDefs
+      Sym "withDefault"
+      Sym "string"
+      StrLit "Hello World"
+ProcTy
+  FormalParams
+    Sym "bool"
+    IdentDefs
+      Sym "foo"
+      Sym "string"
+      StrLit "Proc default"
+  Empty
+'''
+"""
+
+import std/macros
+
+type
+  FooBar = object
+    noDefault: int
+    withDefault = "Hello World"
+
+  SomeProc = proc (foo = "Proc default"): bool
+
+macro dumpBodies() =
+  echo bindSym("FooBar").getTypeImpl().treeRepr
+  echo bindSym("SomeProc").getTypeImpl().treeRepr
+
+dumpBodies()