fix typed void values

compiler/semtypes.nim

@@ -1372,6 +1372,7 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
           "either use ';' (semicolon) or explicitly write each default value")
         message(c.config, a.info, warnImplicitDefaultValue, msg)
       block determineType:
+        var canBeVoid = false
         if kind == skTemplate:
           if typ != nil and typ.kind == tyUntyped:
             # don't do any typechecking or assign a type for
@@ -1382,9 +1383,14 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
             # don't do any typechecking
             def.typ = makeTypeFromExpr(c, def.copyTree)
             break determineType
+          elif typ != nil and typ.kind == tyTyped:
+            canBeVoid = true
         let isGeneric = isCurrentlyGeneric()
         inc c.inGenericContext, ord(isGeneric)
-        def = semExprWithType(c, def, {efDetermineType, efAllowSymChoice}, typ)
+        if canBeVoid:
+          def = semExpr(c, def, {efDetermineType, efAllowSymChoice}, typ)
+        else:
+          def = semExprWithType(c, def, {efDetermineType, efAllowSymChoice}, typ)
         dec c.inGenericContext, ord(isGeneric)
         if def.referencesAnotherParam(getCurrOwner(c)):
           def.flags.incl nfDefaultRefsParam

tests/template/tdefaultparam.nim

@@ -32,3 +32,25 @@ block: # untyped params with default value
   test2:
     s.add "d"
   doAssert s == "abcde"
+  template test3(body: untyped = willNotCompile) =
+    discard
+  test3()
+
+block: # typed params with `void` default value
+  macro foo(x: typed): untyped =
+    result = x
+  template test(body: untyped, alt: typed = (;), maxTries = 3): untyped {.foo.} =
+    body
+    alt
+  var s = "a"
+  test:
+    s.add "b"
+  do:
+    s.add "c"
+  doAssert s == "abc"
+  template test2(body: untyped, alt: typed = s.add("e"), maxTries = 3): untyped =
+    body
+    alt
+  test2:
+    s.add "d"
+  doAssert s == "abcde"