Changing generic weight of `tyGenericParam` (#22143)

This is in reference to a [feature
request](https://github.com/nim-lang/Nim/issues/22142) that I posted.

I'm making this PR to demonstrate the suggested change and expect that
this should be scrutinized

---------

Co-authored-by: Bung <crc32@qq.com>
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

5 files changed, 115 insertions, 0 deletions

diff --git a/tests/overload/issue22142/tfail_implicit_ambiguous.nim b/tests/overload/issue22142/tfail_implicit_ambiguous.nim
new file mode 100644
index 000000000..2586e0877
--- /dev/null
+++ b/tests/overload/issue22142/tfail_implicit_ambiguous.nim
@@ -0,0 +1,10 @@
+discard """
+  errormsg: "ambiguous call"
+"""
+type
+  A[T] = object
+  C = object
+
+proc test[T: A](param: T): bool = false
+proc test(param: A): bool = true
+doAssert test(A[C]()) == true  # previously would pass
diff --git a/tests/overload/issue22142/tfail_nested_pointers.nim b/tests/overload/issue22142/tfail_nested_pointers.nim
new file mode 100644
index 000000000..1603d98cb
--- /dev/null
+++ b/tests/overload/issue22142/tfail_nested_pointers.nim
@@ -0,0 +1,12 @@
+discard """
+  errormsg: "ambiguous call"
+"""
+
+type
+  A[T] = object
+  C = object
+    x:int
+proc p[T: A[ptr]](x:ptr[T]):bool = false
+proc p(x: ptr[A[ptr]]):bool = true
+var a: A[ptr[C]]
+doAssert p(a.addr) == true
diff --git a/tests/overload/issue22142/tfail_object_is_generic.nim b/tests/overload/issue22142/tfail_object_is_generic.nim
new file mode 100644
index 000000000..b46795bd5
--- /dev/null
+++ b/tests/overload/issue22142/tfail_object_is_generic.nim
@@ -0,0 +1,16 @@
+discard """
+  errormsg: "ambiguous call"
+"""
+
+#[
+As of the time of writing `object` needs some special
+treament in order to be considered "generic" in the right
+context when used implicitly
+]#
+
+type
+  C = object
+
+proc test[T: object](param: T): bool = false
+proc test(param: object): bool = true  
+doAssert test(C()) == true  # previously would pass
diff --git a/tests/overload/issue22142/tfail_typeclass_var_invar.nim b/tests/overload/issue22142/tfail_typeclass_var_invar.nim
new file mode 100644
index 000000000..07db65fef
--- /dev/null
+++ b/tests/overload/issue22142/tfail_typeclass_var_invar.nim
@@ -0,0 +1,9 @@
+discard """
+  errormsg: "ambiguous call"
+"""
+
+type C = object
+proc test[T: ptr](param: var T): bool = false
+proc test(param: var ptr): bool = true
+var d: ptr[C]
+doAssert test(d) == true  # previously would pass
diff --git a/tests/overload/issue22142/tissue22142_shouldpass.nim b/tests/overload/issue22142/tissue22142_shouldpass.nim
new file mode 100644
index 000000000..90d4efe51
--- /dev/null
+++ b/tests/overload/issue22142/tissue22142_shouldpass.nim
@@ -0,0 +1,68 @@
+type
+  A[T] = object of RootObj
+  B[T] = object
+  C = object
+    x:int
+
+# change (previously true)
+block:
+  proc test[J;H: A[J];T: B[H]](param: T): bool = false
+  proc test[T](param: B[T]): bool = true
+  doAssert test(B[A[int]]()) == false
+block:  # object is more specific then `T`
+  proc p[H:object;T:ptr[H]](param:T):bool = false
+  proc p[T](param:ptr[T]):bool= true
+  var l: ptr[C]
+  doAssert p(l) == false
+block:
+  proc p[T:A[object]](param:T):bool = false
+  proc p[T](param: A[T]):bool= true
+  doAssert p(A[C]()) == false
+block:
+  proc test[H;T: A[H]](param: T): bool = false
+  proc test(param: A): bool = true
+  doAssert test(A[C]()) == false
+
+# change (previously ambiguous)
+block:
+  proc p[T](a: A[T]): bool = false
+  proc p[T: object](a: T): bool = true
+  doAssert p(A[int]()) == false
+block:  # A is more specific than `object`
+  proc test[T: A](param: T): bool = false
+  proc test[T: object](param: T): bool = true
+  doAssert test(A[int]()) == false
+block:
+  proc test[T: A](param: T): bool = false
+  proc test(param: object): bool = true
+  doAssert test(A[int]()) == false
+block:
+  proc test[H;T: A[H]](param: T): bool = false
+  proc test(param: object): bool = true
+  doAssert test(A[C]()) == false
+block:
+  proc test[H;T: A[B[H]]](param: T): bool = false
+  proc test[T: object](param: T): bool = true
+  doAssert test(A[B[int]]()) == false
+block:
+  #[
+  This was referenced in the nim compiler source (`sumGeneric`) as a case
+  that was supposed to not be ambiguous, yet it was
+  ]#
+  proc test[J;H:A[J]; T: A[H]](param: T): bool = false
+  proc test[H;T: A[H]](param: T): bool = true
+  doAssert test(A[A[C]]()) == false
+block:
+  proc test[J;T:A[J]](param: A[T]): bool = false
+  proc test[T](param: A[T]): bool = true
+  doAssert test(A[A[C]]()) == false
+block:
+  proc test[T](param: A[T]): bool = false
+  proc test[T: object](param: A[T]): bool = true
+  doAssert test(A[C]()) == true
+
+
+block: #anti-regression (object is more specific then `T`)
+  proc test[J;T:A[J]](param: A[T]): bool = false
+  proc test(param: A[A[object]]): bool = true
+  doAssert test(A[A[C]]()) == true
\ No newline at end of file