Fix occurrence typing for is_function/2

Summary:
The actual top type for a function of arity `n` is `FunType(Nil, List.fill(n)(NoneType), AnyType)`, not `FunType(Nil, List.fill(n)(AnyType), AnyType)`, which means the negation of the predicate is not properly computed.

However, due to how intersection is computed (and particularly when it involves dynamic types), using this as a top type for the positive refinement leads to confusing signal, producing `none()` as domain. So this diff only uses it for the negative part.

Reviewed By: michalmuskala

Differential Revision: D85336038

fbshipit-source-id: 663393fe5919274c945435e764132faa4b0e7221

Author: VLanvin

crates/elp/src/resources/test/eqwalizer_tests/eqwater/eqwater-OTP-27.pretty

@@ -680,28 +680,6 @@ error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types
 Expression has type:   number()
 Context expected type: 'ok'
 
-error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types)
-     ┌─ eqwater/src/eqwater.erl:1306:18
-     │
-1306 │ negate_fun(F) -> F.
-     │                  ^
-     │                  │
-     │                  F.
-Expression has type:   fun((number(), number()) -> term()) | 'ok'
-Context expected type: 'ok'
-     │                  
-
-Because in the expression's type:
-  Here the type is a union type with some valid candidates: 'ok'
-  However the following candidate: fun((number(), number()) -> term())
-  Differs from the expected type:  'ok'
-
------------------------------- Detailed message ------------------------------
-
-  fun((number(), number()) -> term()) | 'ok' is not compatible with 'ok'
-  because
-  fun((number(), number()) -> term()) is not compatible with 'ok'
-
 error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types)
      ┌─ eqwater/src/eqwater.erl:1309:45
      │
@@ -710,26 +688,4 @@ error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types
 Expression has type:   fun((term(), term()) -> term())
 Context expected type: 'ok'
 
-error: incompatible_types (See https://fb.me/eqwalizer_errors#incompatible_types)
-     ┌─ eqwater/src/eqwater.erl:1310:22
-     │
-1310 │ negate_fun_neg(F) -> F.
-     │                      ^
-     │                      │
-     │                      F.
-Expression has type:   fun((number(), number()) -> term()) | 'ok'
-Context expected type: 'ok'
-     │                      
-
-Because in the expression's type:
-  Here the type is a union type with some valid candidates: 'ok'
-  However the following candidate: fun((number(), number()) -> term())
-  Differs from the expected type:  'ok'
-
------------------------------- Detailed message ------------------------------
-
-  fun((number(), number()) -> term()) | 'ok' is not compatible with 'ok'
-  because
-  fun((number(), number()) -> term()) is not compatible with 'ok'
-
-41 ERRORS
+39 ERRORS