[java] MissingOverride long-standing issues

[oowekyala]

Affects PMD Version: Since 6.2.0, when the rule was introduced

Rule: MissingOverride

Description: There are 2 long-standing issues with MissingOverride, related to overriding of a method using type parameters of a parameterized supertype. This is caused by its implementation strategy, since it counts bridge methods in a Class file.

The issue is described at length around this line:

pmd/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/bestpractices/MissingOverrideRule.java

Line 286 in 59f1fe2

// This is a good heuristic, though not perfect.

There are already regression tests in the test file:

pmd/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/bestpractices/xml/MissingOverride.xml

Lines 379 to 444 in 59f1fe2

	<test-code>
	<description>Avoid false positives when in ambiguous situation</description>
	<expected-problems>0</expected-problems>
	<code><![CDATA[
	package net.sourceforge.pmd.lang.java.rule.bestpractices.missingoverride;
	import java.util.Comparator;
	public class AmbiguousOverload implements Comparator<StringBuilder> {
	// only one of those overloads is an override, and so there's only one bridge,
	// so we can't choose the inherited overload
	// missing
	public int compare(StringBuilder o1, StringBuilder o2) {
	return 0;
	}
	public int compare(String s, String s2) {
	return 0;
	}
	}
	]]></code>
	</test-code>
	<test-code>
	<description>Avoid false positives when in ambiguous situation</description>
	<expected-problems>0</expected-problems>
	<code><![CDATA[
	package net.sourceforge.pmd.lang.java.rule.bestpractices.missingoverride;
	import net.sourceforge.pmd.lang.ast.Node;
	import net.sourceforge.pmd.lang.java.ast.ASTType;
	import net.sourceforge.pmd.lang.java.ast.AbstractJavaTypeNode;
	import net.sourceforge.pmd.lang.java.ast.JavaNode;
	public abstract class HierarchyWithSeveralBridges<T extends Node> {
	abstract void foo(T node);
	public static abstract class SubclassOne<T extends JavaNode> extends HierarchyWithSeveralBridges<T> {
	// this one could be resolved
	// @Override
	// abstract void foo(T node);
	}
	public static abstract class SubclassTwo<T extends AbstractJavaTypeNode> extends SubclassOne<T> {
	}
	public static class Concrete extends SubclassTwo<ASTType> {
	// bridges: foo(AbstractJavaTypeNode), foo(JavaNode), foo(Node)
	// missing
	void foo(ASTType node) {
	}
	}
	}
	]]></code>
	</test-code>

This may be fixed easily in PMD 7, since we don't use Class files and have all necessary utilities to test for overriding in TypeOps already:

pmd/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/types/TypeOps.java

Line 1317 in 1b13771

public static boolean overrides(JMethodSig m1, JMethodSig m2, JTypeMirror origin) {

pmd/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/types/TypeOps.java

Line 1213 in 1b13771

public static boolean areOverrideEquivalent(JMethodSig m1, JMethodSig m2) {

Expected outcome:

PMD should report violations for the two test cases, this is a false negative

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Fixed by #2800