SI-7232 Fix Java import vs defn. binding precendence

Java Spec:
> A single-type-import declaration d in a compilation unit c
> of package p that imports a type named n shadows, throughout
> c, the declarations of:
>   - any top level type named n declared in another compilation
>     unit of p
>   - any type named n imported by a type-import-on-demand
>     declaration in c
>   - any type named n imported by a static-import-on-demand
>     declaration in c

Scala Spec:
> Bindings of different kinds have a precedence defined on them:
>   1. Definitions and declarations that are local, inherited, or made
>      available by a package clause in the same compilation unit where
>      the definition occurs have highest precedence.
>   2. Explicit imports have next highest precedence.

2 files changed, 26 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index 7a3ab00578..379f56521b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -516,7 +516,13 @@ trait Namers extends MethodSynthesis {
           // Setting the position at the import means that if there is
           // more than one hidden name, the second will not be warned.
           // So it is the position of the actual hidden name.
-          checkNotRedundant(tree.pos withPoint fromPos, from, to)
+          //
+          // Note: java imports have precence over definitions in the same package
+          //       so don't warn for them. There is a corresponding special treatment
+          //       in the shadowing rules in typedIdent to (SI-7232). In any case,
+          //       we shouldn't be emitting warnings for .java source files.
+          if (!context.unit.isJava)
+            checkNotRedundant(tree.pos withPoint fromPos, from, to)
         }
       }
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index d8493d2312..93d24996eb 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -5046,7 +5046,25 @@ trait Typers extends Modes with Adaptations with Tags {
                          else cx.depth - (cx.scope.nestingLevel - defEntry.owner.nestingLevel)
           var impSym: Symbol = NoSymbol      // the imported symbol
           var imports = context.imports      // impSym != NoSymbol => it is imported from imports.head
-          while (!reallyExists(impSym) && !imports.isEmpty && imports.head.depth > symDepth) {
+
+          // Java: A single-type-import declaration d in a compilation unit c of package p
+          // that imports a type named n shadows, throughout c, the declarations of:
+          //
+          //  1) any top level type named n declared in another compilation unit of p
+          //
+          // A type-import-on-demand declaration never causes any other declaration to be shadowed.
+          //
+          // Scala: Bindings of different kinds have a precedence defined on them:
+          //
+          //  1) Definitions and declarations that are local, inherited, or made available by a
+          //     package clause in the same compilation unit where the definition occurs have
+          //     highest precedence.
+          //  2) Explicit imports have next highest precedence.
+          def depthOk(imp: ImportInfo) = (
+               imp.depth > symDepth
+            || (unit.isJava && imp.isExplicitImport(name) && imp.depth == symDepth)
+          )
+          while (!reallyExists(impSym) && !imports.isEmpty && depthOk(imports.head)) {
             impSym = imports.head.importedSymbol(name)
             if (!impSym.exists) imports = imports.tail
           }