JDK-7057297 : Project Coin: diamond erroneously accepts in array initializer expressions
  • Type: Bug
  • Component: tools
  • Sub-Component: javac
  • Affected Version: 7
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: unknown
  • Submitted: 2011-06-21
  • Updated: 2011-12-07
  • Resolved: 2011-09-02
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JDK 7 JDK 8
7u2 b06Fixed 8Fixed
Description
The following program erroneously compiles:

class Foo<X> {}

class BlocksTest {
    void test() {
        Foo<String>[] fooArr = new Foo<>[]{ };
    }
}

Comments
SUGGESTED FIX A webrev of this fix is available at the following URL: http://hg.openjdk.java.net/jdk7u/jdk7u-dev/langtools/rev/8c9f07f9aa28
2011-08-26

SUGGESTED FIX diff --git a/src/share/classes/com/sun/tools/javac/parser/JavacParser.java b/src/share/classes/com/sun/tools/javac/parser/JavacParser.java --- a/src/share/classes/com/sun/tools/javac/parser/JavacParser.java +++ b/src/share/classes/com/sun/tools/javac/parser/JavacParser.java @@ -1397,7 +1397,12 @@ mode = oldmode; if (S.token() == LBRACKET) { JCExpression e = arrayCreatorRest(newpos, t); - if (typeArgs != null) { + if (diamondFound) { + setErrorEndPos(S.prevEndPos()); + reportSyntaxError(newpos, "cannot.create.array.with.diamond"); + return toP(F.at(newpos).Erroneous(List.<JCExpression>of(e))); + } + else if (typeArgs != null) { int pos = newpos; if (!typeArgs.isEmpty() && typeArgs.head.pos != Position.NOPOS) { // note: this should always happen but we should diff --git a/src/share/classes/com/sun/tools/javac/resources/compiler.properties b/src/share/classes/com/sun/tools/javac/resources/compiler.properties --- a/src/share/classes/com/sun/tools/javac/resources/compiler.properties +++ b/src/share/classes/com/sun/tools/javac/resources/compiler.properties @@ -462,6 +462,9 @@ compiler.err.cannot.create.array.with.type.arguments=\ cannot create array with type arguments +compiler.err.cannot.create.array.with.diamond=\ + cannot use ''<>'' in array initializer + # # limits. We don't give the limits in the diagnostic because we expect # them to change, yet we want to use the same diagnostic. These are all
2011-06-21

EVALUATION This is a bug - diamond should only be allowed in class creation expressions. Quoting from JLS SE 7 draft, the grammar of instance creation expression is the following: ClassInstanceCreationExpression: new TypeArgumentsopt TypeDeclSpecifier TypeArgumentsOrDiamondopt ( ArgumentListopt ) ClassBodyopt Primary . new TypeArgumentsopt Identifier TypeArgumentsOrDiamondopt ( ArgumentListopt ) ClassBodyopt TypeArgumentsOrDiamond: TypeArguments <> ArgumentList: Expression ArgumentList , Expression In other words, diamond is only allowed in instance creation expression (that is, in cases where the 'new' keyword is followed by a plain or qualified class name).
2011-06-21