Clean up deprecation message

Author: som-snytt

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

@@ -78,9 +78,9 @@ class CrossVersionChecks extends MiniPhase:
 
     def maybeWarn(annotee: Symbol, annot: Annotation) =
       if !skipWarning then
-        val msg = annot.argumentConstant(0).map(": " + _.stringValue).getOrElse("")
-        val since = annot.argumentConstant(1).map(" since " + _.stringValue).getOrElse("")
-        report.deprecationWarning(em"${annotee.showLocated} is deprecated${since}${msg}", pos)
+        val message = annot.argumentConstantString(0).filter(!_.isEmpty).map(": " + _).getOrElse("")
+        val since = annot.argumentConstantString(1).filter(!_.isEmpty).map(" since " + _).getOrElse("")
+        report.deprecationWarning(em"${annotee.showLocated} is deprecated${since}${message}", pos)
 
     // Also check for deprecation of the companion class for synthetic methods in the companion module
     sym.getAnnotation(defn.DeprecatedAnnot) match

compiler/test-resources/repl/reset-command

@@ -12,7 +12,7 @@ scala> def f(thread: Thread) = thread.stop()
 -- Deprecation Warning: --------------------------------------------------------
 1 | def f(thread: Thread) = thread.stop()
   |                         ^^^^^^^^^^^
-  |method stop in class Thread is deprecated since : see corresponding Javadoc for more information.
+  |method stop in class Thread is deprecated: see corresponding Javadoc for more information.
 def f(thread: Thread): Unit
 
 scala> def resetNoArgsStillWorks = 1

compiler/test-resources/repl/settings-command

@@ -11,7 +11,7 @@ scala> def f(thread: Thread) = thread.stop()
 -- Deprecation Warning: --------------------------------------------------------
 1 | def f(thread: Thread) = thread.stop()
   |                         ^^^^^^^^^^^
-  |method stop in class Thread is deprecated since : see corresponding Javadoc for more information.
+  |method stop in class Thread is deprecated: see corresponding Javadoc for more information.
 def f(thread: Thread): Unit
 
 scala>