Fix forward declarations in shadow scope contexts (#15386)

* Fix forward declarations in shadow scope contexts

* Add testcase for #15385

* Less empty lines

* Fix tests

* Inline isShadowScope

* Add original testcase (with reduced amount of iterations)

* Add testcase without forward decl

tests/macros/tmacros_issues.nim

@@ -39,6 +39,7 @@ true
 false
 true
 false
+1.0
 '''
 """
 
@@ -403,3 +404,79 @@ testEvenOdd5()
 # it works, because the forward decl and definition share the symbol and the compiler is forgiving here
 #testEvenOdd6() #Don't test it though, the compiler may become more strict in the future
 
+# bug #15385
+var captured_funcs {.compileTime.}: seq[NimNode] = @[]
+
+macro aad*(fns: varargs[typed]): typed =
+  result = newStmtList()
+  for fn in fns:
+    captured_funcs.add fn[0]
+    result.add fn
+
+func exp*(x: float): float ## get different error if you remove forward declaration
+
+func exp*(x: float): float {.aad.} =
+  var x1 = min(max(x, -708.4), 709.8)
+  var result: float   ## looks weird because it is taken from template expansion
+  result = x1 + 1.0
+  result
+
+template check_accuracy(f: untyped, rng: Slice[float], n: int, verbose = false): auto =
+
+  proc check_accuracy: tuple[avg_ulp: float, max_ulp: int] {.gensym.} =
+    let k = (rng.b - rng.a) / (float) n
+    var
+      res, x: float
+      i, max_ulp = 0
+      avg_ulp = 0.0
+
+    x = rng.a
+    while (i < n):
+      res = f(x)
+      i.inc
+      x = x + 0.001
+    (avg_ulp, max_ulp)
+  check_accuracy()
+
+discard check_accuracy(exp, -730.0..709.4, 4)
+
+# And without forward decl
+macro aad2*(fns: varargs[typed]): typed =
+  result = newStmtList()
+  for fn in fns:
+    captured_funcs.add fn[0]
+    result.add fn
+
+func exp2*(x: float): float {.aad2.} =
+  var x1 = min(max(x, -708.4), 709.8)
+  var result: float   ## looks weird because it is taken from template expansion
+  result = x1 + 1.0
+  result
+
+template check_accuracy2(f: untyped, rng: Slice[float], n: int, verbose = false): auto =
+
+  proc check_accuracy2: tuple[avg_ulp: float, max_ulp: int] {.gensym.} =
+    let k = (rng.b - rng.a) / (float) n
+    var
+      res, x: float
+      i, max_ulp = 0
+      avg_ulp = 0.0
+
+    x = rng.a
+    while (i < n):
+      res = f(x)
+      i.inc
+      x = x + 0.001
+    (avg_ulp, max_ulp)
+  check_accuracy2()
+
+discard check_accuracy2(exp2, -730.0..709.4, 4)
+
+# And minimized:
+macro aadMin(fn: typed): typed = fn
+
+func expMin: float
+
+func expMin: float {.aadMin.} = 1
+
+echo expMin()