support narrowing in a form true = ...

Summary: - supporting `true = SomeExpression` the same ways as `SomeExpression orelse throw(...)` (aka ?EQWALIZER_ASSERT)

Reviewed By: VLanvin

Differential Revision: D59059904

fbshipit-source-id: d4f52a25c1585e73e33aafc1fefb0c31ac9e915d

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/Elab.scala

@@ -336,6 +336,10 @@ final class Elab(pipelineContext: PipelineContext) {
  check.checkExpr(l, gradualFunType, env1)
  val (patTy, patEnv) = elabPat.elabPat(mPat, gradualFunType, env)
  (patTy, patEnv)
+ case Match(Pats.PatAtom("true"), mExp) if Filters.asTest(mExp).isDefined =>
+ val test = Filters.asTest(mExp).get
+ val env1 = elabGuard.elabGuards(List(Guard(List(test))), env)(checkRedundancy = true)
+ (AtomLitType("true"), env1)
  case Match(mPat, mExp) =>
  val (ty, env1) = elabExpr(mExp, env)
  val (patTy, patEnv) = elabPat.elabPat(mPat, ty, env1)

eqwalizer/test_projects/check/src/type_asserts.erl.check

@@ -122,12 +122,6 @@ scope_neg(A) -> | ERROR |
 -spec assert7( | |
  string() | binary() | |
 ) -> binary(). | |
-assert7(Input) -> | ERROR |
+assert7(Input) -> | OK  |
  true = is_binary(Input), | |
- Input. | | Input.
- | | Expression has type: string() | binary()
- | | Context expected type: binary()
- | | 
- | | string() | binary() is not compatible with binary()
- | | because
- | | string() is not compatible with binary()
+ Input. | |