From 37a7f4825b6953732a3bbea0b80bb211f17b021f Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Mon, 11 Nov 2019 20:55:44 +0100
Subject: [PATCH] Fix #7532: Do not search for ClassTag types are equal

---
 .../src/dotty/tools/dotc/typer/Typer.scala     |  2 +-
 tests/pos/i7532.scala                          | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i7532.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 505da8883248..538b1226093e 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -679,7 +679,7 @@ class Typer extends Namer
    *  @pre We are in pattern-matching mode (Mode.Pattern)
    */
   def tryWithClassTag(tree: Typed, pt: Type)(implicit ctx: Context): Tree = tree.tpt.tpe.dealias match {
-    case tref: TypeRef if !tref.symbol.isClass && !ctx.isAfterTyper =>
+    case tref: TypeRef if !tref.symbol.isClass && !ctx.isAfterTyper && !(tref =:= pt) =>
       require(ctx.mode.is(Mode.Pattern))
       inferImplicit(defn.ClassTagClass.typeRef.appliedTo(tref),
                     EmptyTree, tree.tpt.span)(ctx.retractMode(Mode.Pattern)) match {
diff --git a/tests/pos/i7532.scala b/tests/pos/i7532.scala
new file mode 100644
index 000000000000..173dc7da8d9d
--- /dev/null
+++ b/tests/pos/i7532.scala
@@ -0,0 +1,18 @@
+
+class Tasty {
+  type Term
+  type Select <: Term
+
+  given scala.reflect.ClassTag[Term] = ???
+  given scala.reflect.ClassTag[Select] = ???
+  object Select {
+    def unapply(x: Select): Boolean = ???
+  }
+}
+
+object Foo {
+  def impl(given tasty: Tasty): Unit = {
+    import tasty.{_, given}
+    val Select() = (??? : Term)
+  }
+}
\ No newline at end of file