Fix forward declaration issues in template/macro context (#15091)

* Fix forward declaration issues in template/macro context

* Correct forward declaration resolving for overloads

* Remove old dead code

* WIP consistent gensym ids

* Minimize diff

* Remove obsoleted hack

* Add templInstCounter to give unique IDs to template instantiations

* Remove obsoleted code

* Eh, init in myOpen, not myProcess...

* Remove optNimV019

* Add testcase for #13484

tests/macros/tmacros_issues.nim

@@ -35,6 +35,10 @@ test
 foo1
 foo2
 foo3
+true
+false
+true
+false
 '''
 """
 
@@ -289,3 +293,113 @@ proc main() =
   const fb = Foobar(a: a)
   foobar(fb)
 main()
+
+# bug #13484
+
+proc defForward(id, nid: NimNode): NimNode =
+  result = newProc(id, @[newIdentNode("bool"), newIdentDefs(nid, newIdentNode("int"))], body=newEmptyNode())
+
+proc defEven(evenid, oddid, nid: NimNode): NimNode =
+  result = quote do:
+    proc `evenid`(`nid`: int): bool =
+      if `nid` == 0:
+        return true
+      else:
+        return `oddid`(`nid` - 1)
+
+proc defOdd(evenid, oddid, nid: NimNode): NimNode =
+  result = quote do:
+    proc `oddid`(`nid`: int): bool =
+      if `nid` == 0:
+        return false
+      else:
+        return `evenid`(`nid` - 1)
+
+proc callNode(funid, param: NimNode): NimNode =
+  result = quote do:
+    `funid`(`param`)
+
+macro testEvenOdd3(): untyped =
+  let
+    evenid = newIdentNode("even3")
+    oddid = newIdentNode("odd3")
+    nid = newIdentNode("n")
+    oddForward = defForward(oddid, nid)
+    even = defEven(evenid, oddid, nid)
+    odd = defOdd(evenid, oddid, nid)
+    callEven = callNode(evenid, newLit(42))
+    callOdd = callNode(oddid, newLit(42))
+  result = quote do:
+    `oddForward`
+    `even`
+    `odd`
+    echo `callEven`
+    echo `callOdd`
+
+macro testEvenOdd4(): untyped =
+  let
+    evenid = newIdentNode("even4")
+    oddid = newIdentNode("odd4")
+    nid = newIdentNode("n")
+    oddForward = defForward(oddid, nid)
+    even = defEven(evenid, oddid, nid)
+    odd = defOdd(evenid, oddid, nid)
+    callEven = callNode(evenid, newLit(42))
+    callOdd = callNode(oddid, newLit(42))
+  # rewrite the body of proc node.
+  oddForward[6] = newStmtList()
+  result = quote do:
+    `oddForward`
+    `even`
+    `odd`
+    echo `callEven`
+    echo `callOdd`
+
+macro testEvenOdd5(): untyped =
+  let
+    evenid = genSym(nskProc, "even5")
+    oddid = genSym(nskProc, "odd5")
+    nid = newIdentNode("n")
+    oddForward = defForward(oddid, nid)
+    even = defEven(evenid, oddid, nid)
+    odd = defOdd(evenid, oddid, nid)
+    callEven = callNode(evenid, newLit(42))
+    callOdd = callNode(oddid, newLit(42))
+  result = quote do:
+    `oddForward`
+    `even`
+    `odd`
+    echo `callEven`
+    echo `callOdd`
+
+macro testEvenOdd6(): untyped =
+  let
+    evenid = genSym(nskProc, "even6")
+    oddid = genSym(nskProc, "odd6")
+    nid = newIdentNode("n")
+    oddForward = defForward(oddid, nid)
+    even = defEven(evenid, oddid, nid)
+    odd = defOdd(evenid, oddid, nid)
+    callEven = callNode(evenid, newLit(42))
+    callOdd = callNode(oddid, newLit(42))
+  # rewrite the body of proc node.
+  oddForward[6] = newStmtList()
+  result = quote do:
+    `oddForward`
+    `even`
+    `odd`
+    echo `callEven`
+    echo `callOdd`
+
+# it works
+testEvenOdd3()
+
+# it causes an error (redefinition of odd4), which is correct
+assert not compiles testEvenOdd4()
+
+# it caused an error (still forwarded: odd5)
+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
+

tests/template/tparams_gensymed.nim

@@ -195,3 +195,129 @@ mystate_machine:
   state_push(S1)
   echo state_current()
   state_pop()
+
+# bug #15075
+block: #Doesn't work
+  template genGenTempl: untyped =
+    proc loop(locals: int)
+    proc loop(locals: int) = discard
+  genGenTempl()
+  let pool = loop
+
+block: #Doesn't work
+  macro genGenMacro: untyped =
+    quote do:
+      proc loop(locals: int)
+      proc loop(locals: int) = discard
+  genGenMacro()
+  let pool = loop
+
+block: #This works
+  proc loop(locals: int)
+  proc loop(locals: int) = discard
+  let pool = loop
+
+#Now somewhat recursive:
+type Cont = ref object of RootObj
+  fn*: proc(c: Cont): Cont {.nimcall.}
+
+block: #Doesn't work
+  template genGenTempl(): untyped =
+    proc loop(locals: Cont): Cont
+    proc loop(locals: Cont): Cont =
+      return Cont(fn: loop)
+    proc doServer(): Cont =
+      return Cont(fn: loop)
+  genGenTempl()
+  discard doServer()
+
+block: #Doesn't work
+  macro genGenMacro(): untyped =
+    quote:
+      proc loop(locals: Cont): Cont
+      proc loop(locals: Cont): Cont =
+        return Cont(fn: loop)
+      proc doServer(): Cont =
+        return Cont(fn: loop)
+  genGenMacro()
+  discard doServer()
+
+block: #This works
+  proc loop(locals: Cont): Cont
+  proc loop(locals: Cont): Cont =
+    return Cont(fn: loop)
+  proc doServer(): Cont =
+    return Cont(fn: loop)
+  discard doServer()
+
+#And fully recursive:
+block: #Doesn't work
+  template genGenTempl: untyped =
+    proc loop(locals: int)
+    proc loop(locals: int) = loop(locals)
+  genGenTempl()
+  let pool = loop
+
+block: #Doesn't work
+  macro genGenMacro: untyped =
+    quote do:
+      proc loop(locals: int)
+      proc loop(locals: int) = loop(locals)
+  genGenMacro()
+  let pool = loop
+
+block: #This works
+  proc loop(locals: int)
+  proc loop(locals: int) = loop(locals)
+  let pool = loop
+
+block:
+  template genAndCallLoop: untyped =
+    proc loop() {.gensym.}
+    proc loop() {.gensym.} =
+      discard
+    loop()
+  genAndCallLoop
+
+block: #Fully recursive and gensymmed:
+  template genGenTempl: untyped =
+    proc loop(locals: int) {.gensym.}
+    proc loop(locals: int) {.gensym.} = loop(locals)
+    let pool = loop
+  genGenTempl()
+
+block: #Make sure gensymmed symbol doesn't overwrite the forward decl
+  proc loop()
+  proc loop() = discard
+  template genAndCallLoop: untyped =
+    proc loop() {.gensym.} =
+      discard
+    loop()
+  genAndCallLoop()
+
+template genLoopDecl: untyped =
+  proc loop()
+template genLoopDef: untyped =
+  proc loop() = discard
+block:
+  genLoopDecl
+  genLoopDef
+  loop()
+block:
+  proc loop()
+  genLoopDef
+  loop()
+block:
+  genLoopDecl
+  proc loop() = discard
+  loop()
+
+block: #Gensymmed sym sharing forward decl
+  macro genGenMacro: untyped =
+    let sym = genSym(nskProc, "loop")
+    nnkStmtList.newTree(
+      newProc(sym, body = newEmptyNode()),
+      newCall(sym),
+      newProc(sym, body = newStmtList()),
+    )
+  genGenMacro