Fix #12656 by setting the proper reporter for inlined methods

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

@@ -972,11 +972,13 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
         }
         // Usually `error` is called from within a rewrite method. In this
         // case we need to report the error at the point of the outermost enclosing inline
-        // call. This way, a defensively written rewrite methid can always
+        // call. This way, a defensively written rewrite method can always
         // report bad inputs at the point of call instead of revealing its internals.
         val callToReport = if (enclosingInlineds.nonEmpty) enclosingInlineds.last else call
         val ctxToReport = ctx.outersIterator.dropWhile(enclosingInlineds(using _).nonEmpty).next
-        inContext(ctxToReport) {
+        // The context in which we report should still use the existing context reporter
+        val ctxOrigReporter = ctxToReport.fresh.setReporter(ctx.reporter)
+        inContext(ctxOrigReporter) {
           report.error(message, callToReport.srcPos)
         }
       case _ =>

compiler/test/dotc/run-test-pickling.blacklist

@@ -36,4 +36,5 @@ zero-arity-case-class.scala
 i12194.scala
 i12753
 t6138
-t6138-2
+t6138-2
+i12656.scala

tests/run/i12656.scala

@@ -0,0 +1,16 @@
+transparent inline def expectCompileError(
+  inline code: String,
+  expectedMsg: String
+) =
+  val errors = compiletime.testing.typeCheckErrors(code)
+  assert(errors.head.message == expectedMsg, (errors.head.message, expectedMsg))
+
+transparent inline def expectTypeCheck(
+  inline code: String,
+) : Boolean = compiletime.testing.typeChecks(code)
+
+@main def Test =
+  assert(!expectTypeCheck("""compiletime.error("some error")"""))
+  assert(expectTypeCheck("""1 + 1"""))
+  expectCompileError("""compiletime.error("some error")""", "some error")
+