Memoize SourceFile creation

compiler/src/dotty/tools/dotc/Run.scala

@@ -104,10 +104,10 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
     if (f.isDirectory) {
       ctx.error(s"expected file, received directory '$fileName'")
       NoSource
-    } else if (f.exists) {
-      val encoding = ctx.settings.encoding.value
-      new SourceFile(f, Codec(encoding))
-    } else {
+    }
+    else if (f.exists)
+      ctx.getSource(f)
+    else {
       ctx.error(s"not found: $fileName")
       NoSource
     }

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -1136,8 +1136,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
    */
   def sourceFile(call: Tree)(implicit ctx: Context): SourceFile = {
     val file = call.symbol.sourceFile
-    val encoding = ctx.settings.encoding.value
-    if (file != null && file.exists) new SourceFile(file, Codec(encoding)) else NoSource
+    if (file != null && file.exists) ctx.getSource(file) else NoSource
   }
 
   /** Desugar identifier into a select node. Return the tree itself if not possible */

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

@@ -20,6 +20,8 @@ import config.Settings._
 import config.Config
 import reporting._
 import reporting.diagnostic.Message
+import io.AbstractFile
+import scala.io.Codec
 import collection.mutable
 import printing._
 import config.{JavaPlatform, SJSPlatform, Platform, ScalaSettings}
@@ -224,6 +226,10 @@ object Contexts {
       implicitsCache
     }
 
+    /** Sourcefile corresponding to given abstract file, memoized */
+    def getSource(file: AbstractFile, codec: => Codec = Codec(settings.encoding.value)) =
+      base.sources.getOrElseUpdate(file, new SourceFile(file, codec))
+
     /** Those fields are used to cache phases created in withPhase.
       * phasedCtx is first phase with altered phase ever requested.
       * phasedCtxs is array that uses phaseId's as indexes,
@@ -624,6 +630,9 @@ object Contexts {
 
     def nextId: Int = { _nextId += 1; _nextId }
 
+    /** Sources that were loaded */
+    val sources: mutable.HashMap[AbstractFile, SourceFile] = new mutable.HashMap[AbstractFile, SourceFile]
+
     // Types state
     /** A table for hash consing unique types */
     private[core] val uniques: util.HashSet[Type] = new util.HashSet[Type](Config.initialUniquesCapacity) {
@@ -696,6 +705,7 @@ object Contexts {
     def reset(): Unit = {
       for ((_, set) <- uniqueSets) set.clear()
       errorTypeMsg.clear()
+      sources.clear()
     }
 
     // Test that access is single threaded

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

@@ -61,7 +61,7 @@ object SourceTree {
         case PackageDef(_, stats) =>
           stats.flatMap(sourceTreeOfClass).headOption
         case tree: tpd.TypeDef if tree.symbol == sym =>
-          val sourceFile = new SourceFile(sym.sourceFile, Codec.UTF8)
+          val sourceFile = ctx.getSource(sym.sourceFile, Codec.UTF8)
           Some(SourceTree(tree, sourceFile))
         case _ =>
           None

doc-tool/src/dotty/tools/dottydoc/util/syntax.scala

@@ -21,7 +21,6 @@ object syntax {
 
   implicit class SymbolExtensions(val sym: Symbol) extends AnyVal {
     def sourcePosition(pos: Position)(implicit ctx: Context): SourcePosition =
-      new SourceFile(sym.sourceFile, Codec(ctx.settings.encoding.value)) atPos pos
-
+      ctx.getSource(sym.sourceFile).atPos(pos)
   }
 }