Fix error message for unreducible inline match

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

@@ -1069,7 +1069,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
                 em"""cannot reduce delegate match with
                    | patterns :  ${tree.cases.map(patStr).mkString("\n             ")}"""
               else
-                em"""cannot reduce delegate match with
+                em"""cannot reduce inline match with
                     | scrutinee:  $sel : ${selType}
                     | patterns :  ${tree.cases.map(patStr).mkString("\n             ")}"""
             errorTree(tree, msg)

tests/neg/cannot-reduce-delegate-match.check

@@ -0,0 +1,8 @@
+-- Error: tests/neg/cannot-reduce-delegate-match.scala:4:13 ------------------------------------------------------------
+4 |    delegate match { // error
+  |    ^
+  |    cannot reduce delegate match with
+  |     patterns :  case evidence$1 @ _:Int
+  | This location is in code that was inlined at cannot-reduce-delegate-match.scala:13
+5 |      case _: Int =>
+6 |    }

tests/neg/cannot-reduce-delegate-match.scala

@@ -0,0 +1,14 @@
+object Test {
+
+  inline def bar() =
+    delegate match { // error
+      case _: Int =>
+    }
+
+  {
+    delegate for Int = 9
+    bar()
+  }
+
+  bar()
+}

tests/neg/cannot-reduce-inline-match.check

@@ -0,0 +1,11 @@
+-- Error: tests/neg/cannot-reduce-inline-match.scala:3:13 --------------------------------------------------------------
+3 |    inline x match { // error
+  |    ^
+  |    cannot reduce inline match with
+  |     scrutinee:  {
+  |      "f"
+  |    } : String("f")
+  |     patterns :  case _:Int
+  | This location is in code that was inlined at cannot-reduce-inline-match.scala:9
+4 |      case _: Int =>
+5 |    }

tests/neg/cannot-reduce-inline-match.scala

@@ -0,0 +1,11 @@
+object Test {
+  inline def foo[T](x: T) =
+    inline x match { // error
+      case _: Int =>
+    }
+
+  foo(4)
+
+  foo("f")
+
+}