More restrictive subtyping for tuple() and fun()

Summary: Gradual subtyping for `tuple()` and `fun()` was too lenient, leading to imprecise narrowing/meet operations. Changing it to only allow `tuple() < {none()}` when `tuple()` is under negative polarity. Reviewed By: ilya-klyuchnikov Differential Revision: D51160176 fbshipit-source-id: bf6e58f5b7ac2256c3c9c0042719769dd7cea8e0
WhatsApp · Nov 9, 2023 · a93581e · a93581e
1 parent 2510e16
commit a93581e
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Showing 2 changed files with 13 additions and 6 deletions.
diff --git a/eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/Subtype.scala b/eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/Subtype.scala
@@ -141,21 +141,21 @@ class Subtype(pipelineContext: PipelineContext) {
                 subTypePol(recDecl.fields(fName).tp, fTy, seen)
             }
         }
-      case (AnyTupleType, TupleType(_)) if pipelineContext.gradualTyping =>
+      case (AnyTupleType, TupleType(_)) if pipelineContext.gradualTyping && v1 == - =>
         true
-      case (AnyTupleType, RecordType(_)) if pipelineContext.gradualTyping =>
+      case (AnyTupleType, RecordType(_)) if pipelineContext.gradualTyping && v1 == - =>
         true
-      case (AnyTupleType, RefinedRecordType(_, _)) if pipelineContext.gradualTyping =>
+      case (AnyTupleType, RefinedRecordType(_, _)) if pipelineContext.gradualTyping && v1 == - =>
         true
       case (FunType(_, _, _), AnyFunType) if pipelineContext.gradualTyping =>
         true
-      case (AnyFunType, FunType(_, _, _)) if pipelineContext.gradualTyping =>
+      case (AnyFunType, FunType(_, _, _)) if pipelineContext.gradualTyping && v1 == - =>
         true
       case (FunType(_, argTys, _), AnyFunType) =>
         argTys.forall(subTypePol(AnyType, _, seen))
       case (AnyArityFunType(_), AnyFunType) =>
         true
-      case (AnyFunType, AnyArityFunType(_)) if pipelineContext.gradualTyping =>
+      case (AnyFunType, AnyArityFunType(_)) if pipelineContext.gradualTyping && v1 == - =>
         true
       case (FunType(_, _, resTy1), AnyArityFunType(resTy2)) =>
         subTypePol(resTy1, resTy2, seen)

diff --git a/eqwalizer/test_projects/check_gradual/src/gradual_misc.erl.check b/eqwalizer/test_projects/check_gradual/src/gradual_misc.erl.check
@@ -47,5 +47,12 @@ fuzz03([_ | {}]) ->                        | OK      |
                                            |         |
 -spec refine_tuple_neg(a | {b, c})         |         |
     -> a | {none()}.                       |         |
-refine_tuple_neg(T) when is_tuple(T) -> T; | OK      |
+refine_tuple_neg(T) when is_tuple(T) -> T; | ERROR   | T.
+                                           |         | Expression has type:   none() | {'b', 'c'}
+                                           |         | Context expected type: 'a' | {none()}
+                                           |         | 
+                                           |         |   none() | {'b', 'c'} is not compatible with 'a' | {none()}
+                                           |         |   because
+                                           |         |   {'b', 'c'} is not compatible with 'a' | {none()}
+                                           |         |   expected union does not contain any tuple type of size 2
 refine_tuple_neg(T) -> T.                  |         |