Avoid exception in sourcePosition

Author: odersky

compiler/src/dotty/tools/dotc/interactive/InteractiveDriver.scala

@@ -44,7 +44,9 @@ class InteractiveDriver(settings: List[String]) extends Driver {
 
   def currentCtx: Context = myCtx
 
-  private val myOpenedFiles = new mutable.LinkedHashMap[URI, SourceFile]
+  private val myOpenedFiles = new mutable.LinkedHashMap[URI, SourceFile] {
+    override def default(key: URI) = NoSource
+  }
 
   private val myOpenedTrees = new mutable.LinkedHashMap[URI, List[SourceTree]] {
     override def default(key: URI) = Nil

language-server/src/dotty/tools/languageserver/DottyLanguageServer.scala

@@ -351,9 +351,12 @@ object DottyLanguageServer {
 
   /** Convert an lsp4j.Position to a SourcePosition */
   def sourcePosition(driver: InteractiveDriver, uri: URI, pos: lsp4j.Position): SourcePosition = {
-    val source = driver.openedFiles(uri) // might throw exception
-    val p = Positions.Position(source.lineToOffset(pos.getLine) + pos.getCharacter)
-    new SourcePosition(source, p)
+    val source = driver.openedFiles(uri)
+    if (source.exists) {
+      val p = Positions.Position(source.lineToOffset(pos.getLine) + pos.getCharacter)
+      new SourcePosition(source, p)
+    }
+    else NoSourcePosition
   }
 
   /** Convert a SourcePosition to an lsp4j.Range */