Add test and drop diagnostic output unless debugging

Author: odersky

compiler/src/dotty/tools/dotc/core/Denotations.scala

@@ -610,16 +610,13 @@ object Denotations {
      */
     def signature(sourceLanguage: SourceLanguage)(using Context): Signature =
       if (isType) Signature.NotAMethod // don't force info if this is a type denotation
-      else info match {
+      else info match
         case info: MethodOrPoly =>
           try info.signature(sourceLanguage)
-          catch { // !!! DEBUG
-            case scala.util.control.NonFatal(ex) =>
-              report.echo(s"cannot take signature of $info")
-              throw ex
-          }
+          catch case ex: Exception =>
+            if ctx.debug then report.echo(s"cannot take signature of $info")
+            throw ex
         case _ => Signature.NotAMethod
-      }
 
     def derivedSingleDenotation(symbol: Symbol, info: Type, pre: Type = this.prefix, isRefinedMethod: Boolean = this.isRefinedMethod)(using Context): SingleDenotation =
       if ((symbol eq this.symbol) && (info eq this.info) && (pre eq this.prefix) && (isRefinedMethod == this.isRefinedMethod)) this

tests/neg/i16407.check

@@ -0,0 +1,12 @@
+-- Error: tests/neg/i16407.scala:2:2 -----------------------------------------------------------------------------------
+2 |  f(g()) // error // error
+  |  ^
+  |  cannot resolve reference to type (X.this : Y & X).A
+  |  the classfile defining the type might be missing from the classpath
+  |  or the self type of (X.this : Y & X) might not contain all transitive dependencies
+-- Error: tests/neg/i16407.scala:2:4 -----------------------------------------------------------------------------------
+2 |  f(g()) // error // error
+  |    ^
+  |    cannot resolve reference to type (X.this : Y & X).A
+  |    the classfile defining the type might be missing from the classpath
+  |    or the self type of (X.this : Y & X) might not contain all transitive dependencies

tests/neg/i16407.scala

@@ -0,0 +1,11 @@
+trait X { self: Y =>
+  f(g()) // error // error
+}
+trait Y { self: Z =>
+  type B = A
+  def f(a: B): Unit = ()
+  def g(): A = ???
+}
+trait Z {
+  type A
+}