fix: Fix extracting refinements from intersection types in dynamic select hovers (scala#23640)

closes scala#22919

---------

Co-authored-by: Bulby <26726264+thedrawingcoder-gamer@users.noreply.github.com>
[Cherry-picked b0627b3]

Author: 2 people

presentation-compiler/src/main/dotty/tools/pc/HoverProvider.scala

@@ -13,6 +13,7 @@ import scala.meta.pc.SymbolSearch
 import dotty.tools.dotc.ast.tpd.*
 import dotty.tools.dotc.core.Constants.*
 import dotty.tools.dotc.core.Contexts.*
+import dotty.tools.dotc.core.Decorators.*
 import dotty.tools.dotc.core.Flags.*
 import dotty.tools.dotc.core.Names.*
 import dotty.tools.dotc.core.StdNames.*
@@ -202,12 +203,21 @@ object HoverProvider:
             findRefinement(parent)
           case _ => None
 
-      val refTpe = sel.typeOpt.widen.deepDealiasAndSimplify match
-        case r: RefinedType => Some(r)
-        case t: (TermRef | TypeProxy) => Some(t.termSymbol.info.deepDealiasAndSimplify)
-        case _ => None
-
-      refTpe.flatMap(findRefinement).asJava
+      def extractRefinements(t: Type): List[Type] = t match
+        case r: RefinedType => List(r)
+        case t: (TypeRef | AppliedType) =>
+          // deepDealiasAndSimplify can succeed with no progress, so we have to avoid infinite loops
+          val t1 = t.deepDealiasAndSimplify
+          if t1 == t then Nil
+          else extractRefinements(t1)
+        case t: TermRef => extractRefinements(t.widen)
+        case t: TypeProxy => List(t.termSymbol.info.deepDealiasAndSimplify)
+        case AndType(l , r) => List(extractRefinements(l), extractRefinements(r)).flatten
+        case _ => Nil
+
+      val refTpe: List[Type] = extractRefinements(sel.typeOpt)
+
+      refTpe.flatMap(findRefinement).headOption.asJava
     case _ =>
       ju.Optional.empty().nn
 

presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTermSuite.scala

@@ -783,3 +783,78 @@ class HoverTermSuite extends BaseHoverSuite:
          |""".stripMargin,
       "val thisIsAVeryLongName: Int".hover
     )
+
+  @Test def `intersection_of_selectable-1` =
+    check(
+      """|class Record extends Selectable:
+         |  def selectDynamic(name: String): Any = ???
+         |
+         |type A = Record { val aa: Int }
+         |type B = Record { val bb: String }
+         |type AB = A & B
+         |
+         |val ab: AB = Record().asInstanceOf[AB]
+         |val ab_a = ab.a@@a
+         |""".stripMargin,
+      "val aa: Int".hover
+    )
+
+  @Test def `intersection_of_selectable-2` =
+    check(
+      """|class Record extends Selectable:
+         |  def selectDynamic(name: String): Any = ???
+         |
+         |type A = Record { val aa: Int }
+         |type B = Record { val aa: String }
+         |type AB = A & B
+         |
+         |val ab: AB = Record().asInstanceOf[AB]
+         |val ab_a = ab.a@@a
+         |""".stripMargin,
+      "val aa: Int & String".hover
+    )
+
+  @Test def `intersection_of_selectable-3` =
+    check(
+      """|class Record extends Selectable:
+         |  def selectDynamic(name: String): Any = ???
+         |
+         |type A = Record { val aa: Int }
+         |type B = Record { val bb: String }
+         |type AB = A & B
+         |
+         |val ab: AB = Record().asInstanceOf[AB]
+         |val ab_a = ab.b@@b
+         |""".stripMargin,
+      "val bb: String".hover
+    )
+
+  @Test def `intersection_of_selectable-4` =
+    check(
+      """|class Record extends Selectable:
+         |  def selectDynamic(name: String): Any = ???
+         |
+         |type A = Record { val aa: Int }
+         |type B = Record { val bb: String }
+         |type C = Record { val cc: Float }
+         |type AB = A & B
+         |type ABC = AB & C
+         |
+         |val abc: ABC = Record().asInstanceOf[ABC]
+         |val abc_a = abc.a@@a
+         |""".stripMargin,
+      "val aa: Int".hover
+    )
+
+  @Test def `intersection_of_selectable-5` =
+    check(
+      """|class Record extends Selectable:
+         |  def selectDynamic(name: String): Any = ???
+         |
+         |type AL = List[Int] & Record { val aa: Int }
+         |
+         |val al: AL = ???.asInstanceOf[ABC]
+         |val al_a = al.a@@a
+         |""".stripMargin,
+      "val aa: Int".hover
+    )