Merge pull request #2180 from adriaanm/merge-2.10.1-master

Merge 2.10.1 into master

4 files changed, 57 insertions, 9 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/Trees.scala b/src/compiler/scala/tools/nsc/ast/Trees.scala
index c8b878225e..ab6a400c63 100644
--- a/src/compiler/scala/tools/nsc/ast/Trees.scala
+++ b/src/compiler/scala/tools/nsc/ast/Trees.scala
@@ -342,18 +342,59 @@ trait Trees extends scala.reflect.internal.Trees { self: Global =>
               case tpt: TypeTree =>
                 if (tpt.original != null)
                   transform(tpt.original)
-                else if (tpt.tpe != null && (tpt.wasEmpty || (tpt.tpe exists (tp => locals contains tp.typeSymbol)))) {
-                  tpt.duplicate.clearType()
+                else {
+                  val refersToLocalSymbols = tpt.tpe != null && (tpt.tpe exists (tp => locals contains tp.typeSymbol))
+                  val isInferred = tpt.wasEmpty
+                  if (refersToLocalSymbols || isInferred) {
+                    tpt.duplicate.clearType()
+                  } else {
+                    tpt
+                  }
                 }
-                else tree
+              // If one of the type arguments of a TypeApply gets reset to an empty TypeTree, then this means that:
+              // 1) It isn't empty now (tpt.tpe != null), but it was empty before (tpt.wasEmpty).
+              // 2) Thus, its argument got inferred during a preceding typecheck.
+              // 3) Thus, all its arguments were inferred (because scalac can only infer all or nothing).
+              // Therefore, we can safely erase the TypeApply altogether and have it inferred once again in a subsequent typecheck.
+              // UPD: Actually there's another reason for erasing a type behind the TypeTree
+              // is when this type refers to symbols defined in the tree being processed.
+              // These symbols will be erased, because we can't leave alive a type referring to them.
+              // Here we can only hope that everything will work fine afterwards.
               case TypeApply(fn, args) if args map transform exists (_.isEmpty) =>
                 transform(fn)
-              case This(_) if tree.symbol != null && tree.symbol.isPackageClass =>
+              case EmptyTree =>
                 tree
               case _ =>
                 val dupl = tree.duplicate
-                if (tree.hasSymbolField && (!localOnly || (locals contains tree.symbol)) && !(keepLabels && tree.symbol.isLabel))
-                  dupl.symbol = NoSymbol
+                // Typically the resetAttrs transformer cleans both symbols and types.
+                // However there are exceptions when we cannot erase symbols due to idiosyncrasies of the typer.
+                // vetoXXX local variables declared below describe the conditions under which we cannot erase symbols.
+                //
+                // The first reason to not erase symbols is the threat of non-idempotency (SI-5464).
+                // Here we take care of labels (SI-5562) and references to package classes (SI-5705).
+                // There are other non-idempotencies, but they are not worked around yet.
+                //
+                // The second reason has to do with the fact that resetAttrs itself has limited usefulness.
+                //
+                // First of all, why do we need resetAttrs? Gor one, it's absolutely required to move trees around.
+                // One cannot just take a typed tree from one lexical context and transplant it somewhere else.
+                // Most likely symbols defined by those trees will become borked and the compiler will blow up (SI-5797).
+                // To work around we just erase all symbols and types and then hope that we'll be able to correctly retypecheck.
+                // For ones who're not affected by scalac Stockholm syndrome, this might seem to be an extremely naive fix, but well...
+                //
+                // Of course, sometimes erasing everything won't work, because if a given identifier got resolved to something
+                // in one lexical scope, it can get resolved to something else.
+                //
+                // What do we do in these cases? Enter the workaround for the workaround: resetLocalAttrs, which only destroys
+                // locally defined symbols, but doesn't touch references to stuff declared outside of a given tree.
+                // That's what localOnly and vetoScope are for.
+                if (dupl.hasSymbol) {
+                  val sym = dupl.symbol
+                  val vetoScope = localOnly && !(locals contains sym)
+                  val vetoLabel = keepLabels && sym.isLabel
+                  val vetoThis = dupl.isInstanceOf[This] && sym.isPackageClass
+                  if (!(vetoScope || vetoLabel || vetoThis)) dupl.symbol = NoSymbol
+                }
                 dupl.clearType()
             }
           }
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index a7e4006fbe..f0c2b05951 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -1039,6 +1039,9 @@ abstract class ClassfileParser {
       for (n <- 0 until nClasses) {
         // FIXME: this performs an equivalent of getExceptionTypes instead of getGenericExceptionTypes (SI-7065)
         val cls = pool.getClassSymbol(in.nextChar.toInt)
+        // we call initialize due to the fact that we call Symbol.isMonomorphicType in addThrowsAnnotation
+        // and that method requires Symbol to be forced to give the right answers, see SI-7107 for details
+        cls.initialize
         sym.addThrowsAnnotation(cls)
       }
     }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index c7a4d44588..b4ec90c53e 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -1003,7 +1003,7 @@ trait Implicits {
                 args foreach (getParts(_))
               }
             } else if (sym.isAliasType) {
-              getParts(tp.dealias)
+              getParts(tp.normalize) // SI-7180 Normalize needed to expand HK type refs
             } else if (sym.isAbstractType) {
               getParts(tp.bounds.hi)
             }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index 77b0749c20..3c5e484105 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -929,6 +929,7 @@ trait Namers extends MethodSynthesis {
       // to use. clazz is the ModuleClass. sourceModule works also for classes defined in methods.
       val module = clazz.sourceModule
       for (cda <- module.attachments.get[ConstructorDefaultsAttachment]) {
+        debuglog(s"Storing the template namer in the ConstructorDefaultsAttachment of ${module.debugLocationString}.")
         cda.companionModuleClassNamer = templateNamer
       }
       val classTp = ClassInfoType(parents, decls, clazz)
@@ -1250,8 +1251,11 @@ trait Namers extends MethodSynthesis {
                                   // module's templateNamer to classAndNamerOfModule
                 module.attachments.get[ConstructorDefaultsAttachment] match {
                   // by martin: the null case can happen in IDE; this is really an ugly hack on top of an ugly hack but it seems to work
-                  // later by lukas: disabled when fixing SI-5975, i think it cannot happen anymore
-                  case Some(cda) /*if cma.companionModuleClassNamer == null*/ =>
+                  case Some(cda) =>
+                    if (cda.companionModuleClassNamer == null) {
+                      debugwarn(s"SI-6576 The companion module namer for $meth was unexpectedly null")
+                      return
+                    }
                     val p = (cda.classWithDefault, cda.companionModuleClassNamer)
                     moduleNamer = Some(p)
                     p