make getType nodes of generic insts have full inst type (#22655)

fixes #22639 for the third time

Nodes generated by `getType` for `tyGenericInst` types, instead of
having the original `tyGenericInst` type, will have the type of the last
child (due to the `mapTypeToAst` calls which set the type to the given
argument). This will cause subsequent `getType` calls to lose
information and think it's OK to use the sym of the instantiated type
rather than fully expand the generic instantiation.

To prevent this, update the type of the node from the `mapTypeToAst`
calls to the full generic instantiation type.

compiler/vmdeps.nim

@@ -133,6 +133,8 @@ proc mapTypeToAstX(cache: IdentCache; t: PType; info: TLineInfo;
     if inst:
       if allowRecursion:
         result = mapTypeToAstR(t.lastSon, info)
+        # keep original type info for getType calls on the output node:
+        result.typ = t
       else:
         result = newNodeX(nkBracketExpr)
         #result.add mapTypeToAst(t.lastSon, info)
@@ -141,6 +143,8 @@ proc mapTypeToAstX(cache: IdentCache; t: PType; info: TLineInfo;
           result.add mapTypeToAst(t[i], info)
     else:
       result = mapTypeToAstX(cache, t.lastSon, info, idgen, inst, allowRecursion)
+      # keep original type info for getType calls on the output node:
+      result.typ = t
   of tyGenericBody:
     if inst:
       result = mapTypeToAstR(t.lastSon, info)

tests/generics/timpl_ast.nim

@@ -43,3 +43,38 @@ block: # issues #9899, ##14708
     macro parse(s: static string) =
       result = parseStmt(s)
     parse("type " & implRepr(Option))
+
+block: # issue #22639
+  type
+    Spectrum[N: static int] = object
+      data: array[N, float]
+    AngleInterpolator = object
+      data: seq[Spectrum[60]]
+  proc initInterpolator(num: int): AngleInterpolator =
+    result = AngleInterpolator()
+    for i in 0 ..< num:
+      result.data.add Spectrum[60]()
+  macro genCompatibleTuple(t: typed): untyped =
+    let typ = t.getType[1].getTypeImpl[2]
+    result = nnkTupleTy.newTree()
+    for i, ch in typ: # is `nnkObjectTy`
+      result.add nnkIdentDefs.newTree(ident(ch[0].strVal), # ch is `nnkIdentDefs`
+                                      ch[1],
+                                      newEmptyNode())
+  proc fullSize[T: object | tuple](x: T): int =
+    var tmp: genCompatibleTuple(T)
+    result = 0
+    for field, val in fieldPairs(x):
+      result += sizeof(val)
+    doAssert result == sizeof(tmp)
+
+  let reflectivity = initInterpolator(1)
+  for el in reflectivity.data:
+    doAssert fullSize(el) == sizeof(el)
+  doAssert fullSize(reflectivity.data[0]) == sizeof(reflectivity.data[0])
+  doAssert genCompatibleTuple(Spectrum[60]) is tuple[data: array[60, float]]
+  doAssert genCompatibleTuple(Spectrum[120]) is tuple[data: array[120, float]]
+  type Foo[T] = object
+    data: T
+  doAssert genCompatibleTuple(Foo[int]) is tuple[data: int]
+  doAssert genCompatibleTuple(Foo[float]) is tuple[data: float]