Set positions of inline bindings

Align position of binding and position of its defined symbol. This avoids some test-pickler
errors observed with the new inliner.

Author: odersky

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

@@ -242,9 +242,10 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
       if (isByName) (Method | InlineProxy, ExprType(argtpe.widen))
       else (inlineFlag, argtpe.widen)
     val boundSym = newSym(name, bindingFlags, bindingType).asTerm
-    val binding =
+    val binding = {
       if (isByName) DefDef(boundSym, arg.changeOwner(ctx.owner, boundSym))
       else ValDef(boundSym, arg)
+    }.withPos(boundSym.pos)
     boundSym.defTree = binding
     bindingsBuf += binding
     binding
@@ -297,7 +298,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
           ref(rhsClsSym.sourceModule)
         else
           inlineCallPrefix
-      val binding = ValDef(selfSym.asTerm, rhs)
+      val binding = ValDef(selfSym.asTerm, rhs).withPos(selfSym.pos)
       bindingsBuf += binding
       selfSym.defTree = binding
       inlining.println(i"proxy at $level: $selfSym = ${bindingsBuf.last}")