Not all deprecation warnings reported for types defined in one java file

[iloveeclipse]

In the light of #4553 I've tried to construct a simple exmaple to understand which differences we have before / after the fix 545483d / #4293 with previous ecj version and with latest javac from Java 25.

I run immediately into the problem that ecj doesn't produce all deprecation warnings for types defined in same file (but javac does).

This is "spin off" from #4562.

Consider this one file example with only class level deprecation:

package a;
@Deprecated
public class OldClass {
//    @Deprecated
    public void foo() {
    }
//    @Deprecated
    public void bar() {
    }
}
class ExtendsOldClass extends OldClass {
    @Override
    public void foo() {
        super.foo();
    }
    public void callingFoo() {
        super.foo();
    }
    public void callingBar() {
        bar();
    }
}
class UseOldClass  {
    public void callingFoo() {
        new ExtendsOldClass().foo();
        new OldClass().foo();
    }
    public void callingBar() {
        new ExtendsOldClass().bar();
        new OldClass().bar();
    }
}

javac from Java 25 reports three warnings:

javac -d /tmp/testcompile --release 17 -Xlint:deprecation  /data/workspaces/aloskuto-bf/Deprecation/src/a/*.java 

/data/workspaces/aloskuto-bf/Deprecation/src/a/OldClass.java:11: warning: [deprecation] OldClass in a has been deprecated
class ExtendsOldClass extends OldClass {
                              ^
/data/workspaces/aloskuto-bf/Deprecation/src/a/OldClass.java:26: warning: [deprecation] OldClass in a has been deprecated
        new OldClass().foo();
            ^
/data/workspaces/aloskuto-bf/Deprecation/src/a/OldClass.java:30: warning: [deprecation] OldClass in a has been deprecated
        new OldClass().bar();
            ^
3 warnings

ecj reports nothing on command line if using -warn:+deprecation option:

java -jar ~/Downloads/ecj-I20251026-1800.jar -d /tmp/testcompile --release 17 -warn:+deprecation /data/workspaces/aloskuto-bf/Deprecation/src/a/*.java

... but reports one warning if using project settings below (and this warning is also shown in the editor)

org.eclipse.jdt.core.compiler.problem.deprecation=warning
org.eclipse.jdt.core.compiler.problem.deprecationInDeprecatedCode=disabled
org.eclipse.jdt.core.compiler.problem.deprecationWhenOverridingDeprecatedMethod=enabled

java -jar ~/Downloads/ecj-I20251026-1800.jar -d /tmp/testcompile --release 17 -properties /data/workspaces/aloskuto-bf/Deprecation/.settings/org.eclipse.jdt.core.prefs  /data/workspaces/aloskuto-bf/Deprecation/src/a/*.java
----------
1. WARNING in /data/workspaces/aloskuto-bf/Deprecation/src/a/OldClass.java (at line 13)
        public void foo() {
                    ^^^^^
The method ExtendsOldClass.foo() overrides a deprecated method from OldClass
----------
1 problem (1 warning)

Splitting the code over three files results in a completely different picture and ecj reports more deprecation warnings, but there are issues with that reporting, see #4562.

Expected

ecj should report warnings independently whether the code is in one or multiple files.

[stephan-herrmann]

Here we are indeed facing a "change of rules" (though not a recent one):

In 1996 the rule was

A deprecation warning is suppressed if the compilation unit containing the deprecation is being compiled at the same time as the compilation unit using the deprecated class or member. This allows legacy APIs to be built without warnings. There currently is no other way to suppress the deprecation warnings.

Now, certainly "compiled at the same time" should no longer make a difference in 2025, but the above rule hints at an understanding that compilation unit is the unit of friendliness, where I don't want to be warned about my own deprecations!

Back to the present:

A Java compiler must produce a deprecation warning when [...] unless:

• [...]
• The declaration where the use appears and the declaration of the ordinarily deprecated program element are both within the same outermost class;

So, compilation unit is no longer reference, only outermost class is. Ergo we have another bug to be fixed.

[stephan-herrmann]

Quick check: changing the above structure to

package a;
public class X {
    @Deprecated
    class OldClass { ...
    }
    class ExtendsOldClass extends OldClass {  ...
    }
    class UseOldClass  { ... 
    }
}

while keeping the same content, makes javac remain quiet, too.