treat generic proc param/return type like generic type body

fixes nim-lang#8406, fixes nim-lang#8551, refs nim-lang#8545, refs nim-lang#22607

compiler/semtypes.nim

@@ -1307,6 +1307,9 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
   result = newProcType(c, n.info, prev)
   var check = initIntSet()
   var counter = 0
+  template isCurrentlyGeneric: bool =
+    # genericParams might update as implicit generic params are added
+    genericParams != nil and genericParams.len > 0
 
   for i in 1..<n.len:
     var a = n[i]
@@ -1327,7 +1330,10 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
       hasDefault = a[^1].kind != nkEmpty
 
     if hasType:
+      let isGeneric = isCurrentlyGeneric()
+      inc c.inGenericContext, ord(isGeneric)
       typ = semParamType(c, a[^2], constraint)
+      dec c.inGenericContext, ord(isGeneric)
       # TODO: Disallow typed/untyped in procs in the compiler/stdlib
       if kind in {skProc, skFunc} and (typ.kind == tyTyped or typ.kind == tyUntyped):
         if not isMagic(getCurrOwner(c)):
@@ -1348,7 +1354,7 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
         message(c.config, a.info, warnImplicitDefaultValue, msg)
       block determineType:
         var defTyp = typ
-        if genericParams != nil and genericParams.len > 0:
+        if isCurrentlyGeneric():
           defTyp = nil
           def = semGenericStmt(c, def)
           if hasUnresolvedArgs(c, def):
@@ -1427,11 +1433,12 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
       onDef(a[j].info, arg)
       a[j] = newSymNode(arg)
 
-  var r: PType =
-    if n[0].kind != nkEmpty:
-      semTypeNode(c, n[0], nil)
-    else:
-      nil
+  var r: PType = nil
+  if n[0].kind != nkEmpty:
+    let isGeneric = isCurrentlyGeneric()
+    inc c.inGenericContext, ord(isGeneric)
+    r = semTypeNode(c, n[0], nil)
+    dec c.inGenericContext, ord(isGeneric)
 
   if r != nil and kind in {skMacro, skTemplate} and r.kind == tyTyped:
     # XXX: To implement the proposed change in the warning, just
@@ -1484,7 +1491,7 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
           result.flags.excl tfHasMeta
       result.n.typ = r
 
-  if genericParams != nil and genericParams.len > 0:
+  if isCurrentlyGeneric():
     for n in genericParams:
       if {sfUsed, sfAnon} * n.sym.flags == {}:
         result.flags.incl tfUnresolved

tests/misc/t8545.nim

@@ -14,7 +14,7 @@ proc main() =
   proc foo2(a: static[bool]): bar(a) = 1
   doAssert foo2(true) == 1
 
-  proc foo3(a: static[bool]): bar(cast[static[bool]](a)) = 1
+  proc foo3(a: static[bool]): bar(cast[bool](a)) = 1
   doAssert foo3(true) == 1
 
   proc foo4(a: static[bool]): bar(static(a)) = 1

tests/proc/tstaticsignature.nim

@@ -0,0 +1,71 @@
+when false: # issue #22607, needs proper nkWhenStmt handling
+  proc test[x: static bool](
+    t: (
+      when x:
+        int
+      else:
+        float
+      )
+  ) = discard
+  test[true](1.int)
+  test[false](1.0)
+  doAssert not compiles(test[])
+
+block: # expanded version of t8545
+  template bar(a: static[bool]): untyped =
+    when a:
+      int
+    else:
+      float
+
+  proc main() =
+    proc foo1(a: static[bool]): auto = 1
+    doAssert foo1(true) == 1
+
+    proc foo2(a: static[bool]): bar(a) = 1
+    doAssert foo2(true) == 1
+    doAssert foo2(true) is int
+    doAssert foo2(false) == 1.0
+    doAssert foo2(false) is float
+
+    proc foo3(a: static[bool]): bar(cast[bool](a)) = 1
+    doAssert foo3(true) == 1
+    doAssert foo3(true) is int
+    doAssert foo3(false) == 1.0
+    doAssert foo3(false) is float
+
+    proc foo4(a: static[bool]): bar(static(a)) = 1
+    doAssert foo4(true) == 1
+    doAssert foo4(true) is int
+    doAssert foo4(false) == 1.0
+    doAssert foo4(false) is float
+
+  static: main()
+  main()
+
+block: # issue #8406
+  macro f(x: static[int]): untyped = discard
+  proc g[X: static[int]](v: f(X)) = discard
+
+import macros
+
+block: # issue #8551
+  macro distinctBase2(T: typedesc): untyped =
+    let typeNode = getTypeImpl(T)
+    expectKind(typeNode, nnkBracketExpr)
+    if typeNode[0].typeKind != ntyTypeDesc:
+      error "expected typeDesc, got " & $typeNode[0]
+    var typeSym = typeNode[1]
+
+    typeSym = getTypeImpl(typeSym)
+
+    if typeSym.typeKind != ntyDistinct:
+      error "type is not distinct: " & $typeSym.typeKind
+
+    typeSym = typeSym[0]
+    typeSym
+
+  func distinctBase[T](a: T): distinctBase2(T) = distinctBase2(T)(a)
+
+  type T = distinct int
+  doAssert distinctBase(T(0)) is int