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From "Josh Tynjala (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLEX-35329) Initializing member variable/constant that is [Deprecated] incorrectly throws extra warning
Date Thu, 22 Jun 2017 17:56:00 GMT

    [ https://issues.apache.org/jira/browse/FLEX-35329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16059756#comment-16059756

Josh Tynjala commented on FLEX-35329:


> Initializing member variable/constant that is [Deprecated] incorrectly throws extra warning
> -------------------------------------------------------------------------------------------
>                 Key: FLEX-35329
>                 URL: https://issues.apache.org/jira/browse/FLEX-35329
>             Project: Apache Flex
>          Issue Type: Bug
>          Components: .Unspecified - Compiler
>    Affects Versions: Apache Flex 4.16.0
>            Reporter: Josh Tynjala
>            Assignee: Josh Tynjala
>            Priority: Minor
> Consider the following class:
> {code:title=Deprecated.as}
> package
> {
> 	import flash.display.Sprite;
> 	public class Deprecated extends Sprite
> 	{
> 		[Deprecated]
> 		public static var STATIC_DEPRECATED:String = "static";
> 		[Deprecated]
> 		public static var STATIC_DEPRECATED2:String;
> 		[Deprecated]
> 		public var memberDeprecated:String = "member";
> 		[Deprecated]
> 		public var memberDeprecated2:String;
> 		public function Deprecated()
> 		{
> 			STATIC_DEPRECATED = "new value";
> 			Deprecated.STATIC_DEPRECATED = "new value";
> 			memberDeprecated = "new value";
> 			this.memberDeprecated = "new value";
> 			STATIC_DEPRECATED2 = "new value";
> 			Deprecated.STATIC_DEPRECATED2 = "new value";
> 			memberDeprecated2 = "new value";
> 			this.memberDeprecated2 = "new value";
> 		}
> 	}	
> }
> {code}
> The compiler should give eight warnings for each of the lines in the constructor. However,
it actually gives 10 warnings. Here are the two extra warnings:
> {code}
> /Users/joshtynjala/Desktop/Deprecated/src/Deprecated.as(8): col: 21 Warning: 'STATIC_DEPRECATED'
has been deprecated.
> 		public static var STATIC_DEPRECATED:String = "static";
> 		                  ^
> /Users/joshtynjala/Desktop/Deprecated/src/Deprecated.as(14): col: 14 Warning: 'memberDeprecated'
has been deprecated.
> 		public var memberDeprecated:String = "member";
> 		           ^
> {code}
> Notice that there are no warnings for STATIC_DEPRECATED2 and memberDeprecated2 because
they are not initialized. It's only when a member or static variable is initialized that the
warnings are shown. It appears that when the compiler checks for usage of deprecated variables
is a little too aggressive.
> The Falcon compiler and Adobe's ASC 2.0 compiler do not give these same extra warnings.
They only give a warning on actual usage.
> These warnings make it difficult to deprecate a constant or another variable in an open
source library. It makes compile-time noisy with a lot of warnings that need to be ignored.
> Note: When compiling with a library in SWC form, the compiler does not show these warnings.
I suspect that this is why this was never really encountered with the Flex framework, since
the SWCs are pre-compiled. However, for many open source libraries, developers often simply
use the source code with the -source-path compiler option instead of a pre-compiled SWC. That's
when these warnings can be seen. As a long-time library developer, I never used [Deprecated]
metadata because of this bug.
> Solution, which I will implement:
> In LintEvaluator, modify evaluate( Context cx, SetExpressionNode node ).
> {code}
> if (slot != null && !(node.expr instanceof QualifiedIdentifierNode))
> {
> 	//if it's a qualified identifier node, then it's a member/static
> 	//variable on a class that is being initialized, like this:
> 	//public var memberVar:String = "hi";
> 	//this case should not have a warning!
> 	checkDeprecatedSlot(cx, node.expr, node.ref, slot);
> }
> {code}
> The declaration of a member/static variable is a QualifiedIdentifierNode (qualified meaning
that it has modifiers like public/private, static, etc.), but actual usage will be an IdentifierNode
instead. So, if it's a QualifiedIdentifierNode, we know that we don't need to check if the
variable is deprecated or not.

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