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Java Forum / General / November 2007Is this syntactically valid Java?
Is the following syntactically valid? public class Foo { public static void main(String[] args) { for( foo: ; ; ); // Note statement label } } javac is rejecting this, but IntelliJ is saying that it is valid. I would appreciate a reference to the JLS if possible, so I can file a bug report either with Sun or with JetBrains.  SignatureC. Benson Manica | I appreciate all corrections, polite or otherwise. cbmanica(at)gmail.com | ----------------------| I do not currently read any posts posted through sdf.lonestar.org | Google groups, due to rampant unchecked spam. > Is the following syntactically valid? > [quoted text clipped - 7 lines] > would appreciate a reference to the JLS if possible, so I can file a > bug report either with Sun or with JetBrains. I don't know if it is valid or not but why would you want to write code like this? What is is supposed to do? SignatureKnute Johnson email s/nospam/knute/ >> public class Foo { >> public static void main(String[] args) { >> for( foo: ; ; ); // Note statement label >> } >> } > I don't know if it is valid or not but why would you want to write code > like this? What is is supposed to do? I have no interest in writing any such code, I merely wish to determine whether there is a bug in my IDE or javac. I certainly don't know what the code would do. SignatureC. Benson Manica | I appreciate all corrections, polite or otherwise. cbmanica(at)gmail.com | ----------------------| I do not currently read any posts posted through sdf.lonestar.org | Google groups, due to rampant unchecked spam. > Is the following syntactically valid? > [quoted text clipped - 7 lines] > would appreciate a reference to the JLS if possible, so I can file a > bug report either with Sun or with JetBrains. This does not compile in Eclipse JLS Third Edition section 14.14 'The for Statement' and sub sections get the spec at http://java.sun.com/docs/books/jls/ On Wed, 7 Nov 2007 15:25:22 +0000 (UTC), Christopher Benson-Manica <ataru@vinland.freeshell.org> wrote, quoted or indirectly quoted someone who said : > for( foo: ; ; ); // Note statement label Why does it matter? It is meaningless nonsense? Are you writing a compiler? SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >> for( foo: ; ; ); // Note statement label > Why does it matter? It is meaningless nonsense? Yes, it's meaningless. > Are you writing a compiler? No. I am trying to determine whether to file a bug report with JetBrains. (After reading the JLS, I believe the answer is "yes".) SignatureC. Benson Manica | I appreciate all corrections, polite or otherwise. cbmanica(at)gmail.com | ----------------------| I do not currently read any posts posted through sdf.lonestar.org | Google groups, due to rampant unchecked spam. > Is the following syntactically valid? > [quoted text clipped - 7 lines] > would appreciate a reference to the JLS if possible, so I can file a > bug report either with Sun or with JetBrains. I believe it is not syntactically valid. The remainder of this message is of interest only to extreme language lawyers. I'm going to show the available productions, and the JLS sections where I found them. This is based on the third editions, http://java.sun.com/docs/books/jls/third_edition/html/j3TOC.html First note that "for" is a reserved word, and as far as I can tell appears only in for statement productions in 14.14. The statement cannot be a EnhancedForStatement because it requires a ":" followed by an expression. 14.14.2 Now consider it as a BasicForStatement, 14.14.1. In each production, the portion between the "for(" and the first of the required three semicolons is an optional ForInit. The question becomes whether "foo:" can be a ForInit. ForInit: StatementExpressionList LocalVariableDeclaration Can "foo:" be a StatementExpressionList? StatementExpressionList: StatementExpression StatementExpressionList , StatementExpression (14.14.1) Since "foo:" does not contain a ",", it would have to be a single StatementExpression. In 14.8: StatementExpression: Assignment PreIncrementExpression PreDecrementExpression PostIncrementExpression PostDecrementExpression MethodInvocation ClassInstanceCreationExpression "foo:" does not match any of these. Now consider the LocalVariableDeclaration case. In 14.4: LocalVariableDeclaration: VariableModifiers Type VariableDeclarators In 8.4.1: VariableModifiers: VariableModifier VariableModifiers VariableModifier VariableModifier: one of final Annotation so "foo:" does not match VariableModifiers. "foo" could be a type, but then ":" would have to match VariableDeclarators. In 8.3: VariableDeclarators: VariableDeclarator VariableDeclarators , VariableDeclarator VariableDeclarator: VariableDeclaratorId VariableDeclaratorId = VariableInitializer VariableDeclaratorId: Identifier VariableDeclaratorId [ ] All cases of VariableDeclarators begin with an identifier, and ":" is not a valid identifier. Patricia Patricia Shanahan wrote : > The remainder of this message is of interest only to extreme language > lawyers. ! SignatureWojtek :-) > I believe it is not syntactically valid. (snip excellent response) Thank you *very* much. I feel much more comfortable now with reporting this (obscure!) parsing bug to the JetBrains people. SignatureC. Benson Manica | I appreciate all corrections, polite or otherwise. cbmanica(at)gmail.com | ----------------------| I do not currently read any posts posted through sdf.lonestar.org | Google groups, due to rampant unchecked spam. > Is the following syntactically valid? > [quoted text clipped - 7 lines] > would appreciate a reference to the JLS if possible, so I can file a > bug report either with Sun or with JetBrains. To me it seems not to be allowed, but purely for BNF reasons. The first part in for must contain a StatementExpression, while a LabeledStatement is not a StatementExpression as far as I can tell. From JSL (3rd Ed.), but IANAL. Michael > Is the following syntactically valid? > public class Foo { [quoted text clipped - 5 lines] > would appreciate a reference to the JLS if possible, so I can file a > bug report either with Sun or with JetBrains. yes this is my footer >> Is the following syntactically valid? >> public class Foo { [quoted text clipped - 7 lines] > > yes If you are saying it is syntactically valid, could you give your reasoning? In response to the quoted message, I went through the relevant productions in the grammar in the JLS, and did not think it was possible to generate the label in the for. See http://groups.google.com/group/comp.lang.java.programmer/msg/008b9ce336a09d3e However, I could be wrong about it because it is easy to miss something when doing manual processing of a large formal grammar. Patricia Christopher Benson-Manica wrote: >>> Is the following syntactically valid? >>> public class Foo { [quoted text clipped - 5 lines] >>> would appreciate a reference to the JLS if possible, so I can file a >>> bug report either with Sun or with JetBrains. derek wrote: >> yes > If you are saying it is syntactically valid, could you give your reasoning? > [quoted text clipped - 5 lines] > However, I could be wrong about it because it is easy to miss something > when doing manual processing of a large formal grammar. derek is mistaken. Here's what I get from Java 6 (with the loop on line 41): > $ javac -d ../build/classes/ testit/Foo.java > testit/Foo.java:41: not a statement [quoted text clipped - 8 lines] > 3 errors > $ Contrariwise, if I eliminate the "foo: " from the line: > $ javac -d ../build/classes/ testit/Foo.java > $ > $ javac -version > javac 1.6.0_03 > $ SignatureLew > Christopher Benson-Manica wrote: >>>> Is the following syntactically valid? [quoted text clipped - 27 lines] >> testit/Foo.java:41: not a statement >> for( foo: ; ; ); // Note statement label ... I'm not sure that is determinative in the context of this thread. The original issue was that javac rejects code that IntilliJ accepted. I think, based on my previous analysis, that javac is correct and IntelliJ got it wrong, but maybe derek has a valid argument the other way round? Patricia Lew wrote: >> derek is mistaken. Here's what I get from Java 6 (with the loop on >> line 41): >> >>> $ javac -d ../build/classes/ testit/Foo.java >>> testit/Foo.java:41: not a statement >>> for( foo: ; ; ); // Note statement label > I'm not sure that is determinative in the context of this thread. The > original issue was that javac rejects code that IntilliJ accepted. I > think, based on my previous analysis, that javac is correct and IntelliJ > got it wrong, but maybe derek has a valid argument the other way round? Twenty bucks says he doesn't. SignatureLew > Lew wrote: > >> derek is mistaken. Here's what I get from Java 6 (with the loop on [quoted text clipped - 8 lines] > > got it wrong, but maybe derek has a valid argument the other way round? > Twenty bucks says he doesn't. Congrats you get twenty bucks. I have no valid argument. I was testing out something with my newsgroup posting software. I picked an old thread that i didnt think anyone was paying attention to and posted "yes" to it without even reading the thread. Next time i need to test something i will post to the testing group. Sorry bout that.... :) >> Lew wrote: >>>> derek is mistaken. Here's what I get from Java 6 (with the loop on [quoted text clipped - 15 lines] > Next time i need to test something i will post to the testing group. > Sorry bout that.... :) Most news readers that I've used will boost the thread to the top of the list when new activity is posted to it. Even if that wasn't the case, the test group you mentioned is *exactly* for this purpose :-) SignatureDaniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/> Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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