Revert #11784

The original PR fixes a trivial issue. However, the fix has both false
positives and negatives. It's not easy to do the right thing. Therefore,
it's simpler to remove the original fixes.

Author: liufengyun

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -4364,65 +4364,11 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         withMode(Mode.GadtConstraintInference) {
           TypeComparer.constrainPatternType(tree.tpe, pt)
         }
-
-        // approximate type params with bounds
-        def approx = new ApproximatingTypeMap {
-          var alreadyExpanding: List[TypeRef] = Nil
-          def apply(tp: Type) = tp.dealias match
-            case tp: TypeRef if !tp.symbol.isClass =>
-              if alreadyExpanding contains tp then tp else
-                val saved = alreadyExpanding
-                alreadyExpanding ::= tp
-                val res = expandBounds(tp.info.bounds)
-                alreadyExpanding = saved
-                res
-            case _ =>
-              mapOver(tp)
-        }
-
-        // Is it possible that a value of `clsA` is equal to a value of `clsB`?
-        //  This ignores user-defined equals methods, but makes an exception
-        //  for numeric classes.
-        def canOverlap(clsA: ClassSymbol, clsB: ClassSymbol): Boolean =
-          clsA.mayHaveCommonChild(clsB)
-          || clsA.isNumericValueClass // this is quite coarse, but matches to what was done before
-          || clsB.isNumericValueClass
-
-        // Can type `a` possiblly have a common instance with type `b`?
-        def canEqual(a: Type, b: Type): Boolean = trace(i"canEqual $a $b"):
-          b match
-            case _: TypeRef | _: AppliedType if b.typeSymbol.isClass =>
-              a match
-                case a: TermRef if a.symbol.isOneOf(Module | Enum) =>
-                     (a frozen_<:< b) // fast track
-                  || (a frozen_<:< approx(b))
-                case _: TypeRef | _: AppliedType if a.typeSymbol.isClass =>
-                  if a.isNullType then !b.isNotNull
-                  else canOverlap(a.typeSymbol.asClass, b.typeSymbol.asClass)
-                case a: TypeProxy =>
-                  canEqual(a.superType, b)
-                case a: AndOrType =>
-                  canEqual(a.tp1, b) || canEqual(a.tp2, b)
-            case b: TypeProxy =>
-              canEqual(a, b.superType)
-            case b: AndOrType =>
-              // we lose precision with and/or types, but it's hard to do better and
-              // still compute `canEqual(A & B, B & A) = true`.
-              canEqual(a, b.tp1) || canEqual(a, b.tp2)
-
-        if !canEqual(tree.tpe, pt) then
-          // We could check whether `equals` is overridden.
-          // Reasons for not doing so:
-          // - it complicates the protocol
-          // - such code patterns usually implies hidden errors in the code
-          // - it's safe/sound to reject the code
-          report.error(TypeMismatch(tree.tpe, pt, Some(tree), "\npattern type is incompatible with expected type"), tree.srcPos)
-        else
-          val cmp =
-            untpd.Apply(
-              untpd.Select(untpd.TypedSplice(tree), nme.EQ),
-              untpd.TypedSplice(dummyTreeOfType(pt)))
-          typedExpr(cmp, defn.BooleanType)
+        val cmp =
+          untpd.Apply(
+            untpd.Select(untpd.TypedSplice(tree), nme.EQ),
+            untpd.TypedSplice(dummyTreeOfType(pt)))
+        typedExpr(cmp, defn.BooleanType)
       case _ =>
 
   private def checkInterestingResultInStatement(t: Tree)(using Context): Boolean = {