Force compile errors for missing implicits in `Discovered` materialization to point at their source methods, for easier fixing

2 files changed, 30 insertions, 2 deletions

diff --git a/core/src/test/scala/mill/discover/DiscoveredTests.scala b/core/src/test/scala/mill/discover/DiscoveredTests.scala
index dae7ff1b..843ec474 100644
--- a/core/src/test/scala/mill/discover/DiscoveredTests.scala
+++ b/core/src/test/scala/mill/discover/DiscoveredTests.scala
@@ -1,7 +1,9 @@
 package mill.discover
 
+import java.io.InputStreamReader
+
 import utest._
-import mill.Module
+import mill.{Module, T}
 import mill.util.TestUtil.test
 object DiscoveredTests extends TestSuite{
 
@@ -48,5 +50,32 @@ object DiscoveredTests extends TestSuite{
       )
       assert(mapped.toSet == expected.toSet)
     }
+    'compileError - {
+      'unserializableTarget - {
+
+        object outer extends Module {
+          def single = mill.T{ new InputStreamReader(System.in) }
+        }
+
+        val error = compileError("Discovered[outer.type]")
+        assert(
+          error.msg.contains("could not find implicit value"),
+          error.pos.contains("def single = mill.T{ new InputStreamReader(System.in) }")
+        )
+      }
+
+      'unreadableCommand - {
+        object outer extends Module {
+          def single(in: InputStreamReader) = mill.T.command{ println(123) }
+        }
+
+        val error = compileError("Discovered[outer.type]")
+
+        assert(
+          error.msg.contains("could not find implicit value"),
+          error.pos.contains("def single(in: InputStreamReader) = mill.T.command{ println(123) }")
+        )
+      }
+    }
   }
 }
diff --git a/core/src/test/scala/mill/eval/EvaluationTests.scala b/core/src/test/scala/mill/eval/EvaluationTests.scala
index ccb476e7..9a177b58 100644
--- a/core/src/test/scala/mill/eval/EvaluationTests.scala
+++ b/core/src/test/scala/mill/eval/EvaluationTests.scala
@@ -5,7 +5,6 @@ import mill.util.TestUtil.{Test, test}
 import mill.define.{Target, Task}
 import mill.{Module, T}
 import mill.discover.Discovered
-import mill.eval.Evaluator
 import mill.util.{OSet, TestUtil}
 import utest._
 import utest.framework.TestPath