Revert "Remove DottyBackendInterface.sourcePos"

This reverts commit c0e01e9.

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala

@@ -664,7 +664,7 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
       var elemKind = arr.elementType
       val argsSize = args.length
       if (argsSize > dims) {
-        ctx.error(s"too many arguments for array constructor: found ${args.length} but array has only $dims dimension(s)", app.sourcePos)
+        ctx.error(s"too many arguments for array constructor: found ${args.length} but array has only $dims dimension(s)", sourcePos(app.span))
       }
       if (argsSize < dims) {
         /* In one step:

compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala

@@ -59,7 +59,7 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
       outputDirectory
     } catch {
       case ex: Throwable =>
-        ctx.error(s"Couldn't create file for class $cName\n${ex.getMessage}", csym.sourcePos)
+        ctx.error(s"Couldn't create file for class $cName\n${ex.getMessage}", sourcePos(csym.span))
         null
     }
   }

compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala

@@ -404,7 +404,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
         val loc = Local(tk, sym.name.mangledString.toString, nxtIdx, sym.is(Flags.Synthetic))
         val existing = slots.put(sym, loc)
         if (existing.isDefined)
-          ctx.error("attempt to create duplicate local var.", sym.sourcePos)
+          ctx.error("attempt to create duplicate local var.", sourcePos(sym.span))
         assert(tk.size > 0, "makeLocal called for a symbol whose type is Unit.")
         nxtIdx += tk.size
         loc
@@ -454,7 +454,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
     }
     def lineNumber(tree: Tree): Unit = {
       if (!emitLines || !tree.span.exists) return;
-      val nr = tree.sourcePos.line + 1
+      val nr = sourcePos(tree.span).line + 1
       if (nr != lastEmittedLineNr) {
         lastEmittedLineNr = nr
         lastInsn match {
@@ -557,7 +557,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
 
       if (params.size > MaximumJvmParameters) {
         // SI-7324
-        ctx.error(s"Platform restriction: a parameter list's length cannot exceed $MaximumJvmParameters.", methSymbol.sourcePos)
+        ctx.error(s"Platform restriction: a parameter list's length cannot exceed $MaximumJvmParameters.", sourcePos(methSymbol.span))
         return
       }
 
@@ -586,7 +586,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
               ctx.error("Concrete method has no definition: " + dd + (
                 if (ctx.settings.Ydebug.value) "(found: " + methSymbol.owner.info.decls.toList.mkString(", ") + ")"
                 else ""),
-                ctx.source.atSpan(NoSpan)
+                sourcePos(NoSpan)
               )
             case _ =>
               bc emitRETURN returnType

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -75,6 +75,8 @@ class DottyBackendInterface(val outputDirectory: AbstractFile, val superCallsMap
     ctx.error(msg)
     throw new RuntimeException(msg)
   }
+  def sourcePos(pos: Spans.Span)(implicit ctx: Context): util.SourcePosition =
+    ctx.source.atSpan(pos)
 
   val perRunCaches: Caches = new Caches {
     def newAnyRefMap[K <: AnyRef, V](): mutable.AnyRefMap[K, V] = new mutable.AnyRefMap[K, V]()
@@ -325,7 +327,7 @@ class DottyBackendInterface(val outputDirectory: AbstractFile, val superCallsMap
     def _1: Type = field.tpe match {
       case JavaArrayType(elem) => elem
       case _ =>
-        ctx.error(s"JavaSeqArray with type ${field.tpe} reached backend: $field", field.sourcePos)
+        ctx.error(s"JavaSeqArray with type ${field.tpe} reached backend: $field", sourcePos(field.span))
         UnspecifiedErrorType
     }
     def _2: List[Tree] = field.elems