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Avoid existing methods when renaming near-miss Object methods #974

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9267c02
RenameMethodsNamedHashcodeEqualOrToString: do not rename onto an exis…
martinfrancois Aug 10, 2026
4d67238
Review fixes: also reject same-file subtype collisions, and non-publi…
timtebeek Aug 11, 2026
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timtebeek Aug 11, 2026
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43 changes: 40 additions & 3 deletions src/main/java/org/openrewrite/staticanalysis/RenameMethodsNamedHashcodeEqualOrToString.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,13 +24,16 @@
import org.openrewrite.java.JavaIsoVisitor;
import org.openrewrite.java.MethodMatcher;
import org.openrewrite.java.search.DeclaresMethod;
import org.openrewrite.java.tree.Flag;
import org.openrewrite.java.tree.J;
import org.openrewrite.java.tree.JavaSourceFile;
import org.openrewrite.java.tree.JavaType;
import org.openrewrite.java.tree.TypeUtils;
import org.openrewrite.staticanalysis.java.JavaFileChecker;

import java.time.Duration;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;

import static java.util.Collections.singleton;

Expand Down Expand Up @@ -63,17 +66,51 @@ public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method, Ex
String sn = method.getSimpleName();
JavaType rte = method.getReturnTypeExpression().getType();
JavaType.Method t = method.getMethodType();
if (equalsIgnoreCaseExclusive(sn, "hashCode") && JavaType.Primitive.Int == rte && NO_ARGS.matches(t)) {
if (equalsIgnoreCaseExclusive(sn, "hashCode") && JavaType.Primitive.Int == rte && NO_ARGS.matches(t) && canRenameTo(t, "hashCode", NO_ARGS)) {
doAfterVisit(new ChangeMethodName(MethodMatcher.methodPattern(method), "hashCode", true, false).getVisitor());
} else if ("equal".equalsIgnoreCase(sn) && JavaType.Primitive.Boolean == rte && OBJECT_ARG.matches(t)) {
} else if ("equal".equalsIgnoreCase(sn) && JavaType.Primitive.Boolean == rte && OBJECT_ARG.matches(t) && canRenameTo(t, "equals", OBJECT_ARG)) {
doAfterVisit(new ChangeMethodName(MethodMatcher.methodPattern(method), "equals", true, false).getVisitor());
} else if (equalsIgnoreCaseExclusive(sn, "toString") && TypeUtils.isString(rte) && NO_ARGS.matches(t)) {
} else if (equalsIgnoreCaseExclusive(sn, "toString") && TypeUtils.isString(rte) && NO_ARGS.matches(t) && canRenameTo(t, "toString", NO_ARGS)) {
doAfterVisit(new ChangeMethodName(MethodMatcher.methodPattern(method), "toString", true, false).getVisitor());
}
}
return super.visitMethodDeclaration(method, ctx);
}

/**
* Method names are case sensitive, so a type may legally declare both the near-miss and the correctly
* named method; renaming would emit a duplicate. The rename reaches overrides too, so subtypes in the
* same file must be free of the target as well, and renaming onto an inherited `final` method or onto
* one of `Object`'s public instance methods would emit an illegal override.
* <p>
* Declarations come from the LST rather than the type model, which for records and Lombok `@Data`
* classes also carries generated members an explicit declaration would replace rather than collide with.
*/
private boolean canRenameTo(JavaType.Method methodType, String targetName, MethodMatcher signature) {
Set<Flag> flags = methodType.getFlags();
if (!flags.contains(Flag.Public) || flags.contains(Flag.Static)) {
return false;
}
JavaType.FullyQualified declaringType = methodType.getDeclaringType();
AtomicBoolean targetAlreadyDeclared = new AtomicBoolean();
new JavaIsoVisitor<AtomicBoolean>() {
@Override
public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration existing, AtomicBoolean declared) {
JavaType.Method existingType = existing.getMethodType();
if (existingType != null && targetName.equals(existing.getSimpleName()) &&
signature.matches(existingType) &&
TypeUtils.isAssignableTo(declaringType, existingType.getDeclaringType())) {
declared.set(true);
}
return super.visitMethodDeclaration(existing, declared);
}
}.visit(getCursor().firstEnclosingOrThrow(JavaSourceFile.class), targetAlreadyDeclared);
return !targetAlreadyDeclared.get() &&
!TypeUtils.findDeclaredMethod(declaringType.getSupertype(), targetName, methodType.getParameterTypes())
.filter(m -> m.getFlags().contains(Flag.Final))
.isPresent();
}

private boolean equalsIgnoreCaseExclusive(String inputToCheck, String targetToCheck) {
return inputToCheck.equalsIgnoreCase(targetToCheck) && !inputToCheck.equals(targetToCheck);
}
Expand Down
309 changes: 308 additions & 1 deletion ...st/java/org/openrewrite/staticanalysis/RenameMethodsNamedHashcodeEqualOrToStringTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,8 +21,9 @@
import org.openrewrite.test.RewriteTest;

import static org.openrewrite.java.Assertions.java;
import static org.openrewrite.java.Assertions.version;

@SuppressWarnings({"MethodMayBeStatic", "MisspelledEquals", "BooleanMethodNameMustStartWithQuestion"})
@SuppressWarnings({"MethodMayBeStatic", "MisspelledEquals", "BooleanMethodNameMustStartWithQuestion", "unused"})
class RenameMethodsNamedHashcodeEqualOrToStringTest implements RewriteTest {

@Override
Expand Down Expand Up @@ -113,4 +114,310 @@ public int hashcode(int a, int b) {
)
);
}

@Test
void doNotRenameWhenTargetIsAlreadyDeclared() {
rewriteRun(
//language=java
java(
"""
class Test {
public int hashcode() {
return 1;
}

public int hashCode() {
return 2;
}

public boolean equal(Object value) {
return false;
}

public boolean equals(Object value) {
return true;
}

public String tostring() {
return "near";
}

public String toString() {
return "proper";
}
}
"""
)
);
}

@Test
void doNotRenameWhenInterfaceAlreadyDeclaresTarget() {
rewriteRun(
//language=java
java(
"""
interface ITest {
int hashcode();

int hashCode();

boolean equal(Object obj);

boolean equals(Object obj);

String tostring();

String toString();
}
"""
)
);
}

@Test
void doNotRenameWhenEnumAlreadyDeclaresTarget() {
rewriteRun(
//language=java
java(
"""
enum Test {
A;

public String tostring() {
return "near";
}

@Override
public String toString() {
return "proper";
}
}
"""
)
);
}

@Test
void doNotRenameWhenRecordAlreadyDeclaresTarget() {
rewriteRun(
version(
//language=java
java(
"""
record Test(int value) {
public int hashcode() {
return 1;
}

@Override
public int hashCode() {
return 2;
}
}
"""
), 17)
);
}

@Test
void renameWhenRecordDoesNotExplicitlyDeclareTarget() {
rewriteRun(
version(
//language=java
java(
"""
record Test(int value) {
public int hashcode() {
return 1;
}
}
""",
"""
record Test(int value) {
public int hashCode() {
return 1;
}
}
"""
), 17)
);
}

@Test
void doNotRenameWhenInheritedTargetIsFinal() {
rewriteRun(
//language=java
java(
"""
class Base {
@Override
public final int hashCode() {
return 1;
}
}

class Test extends Base {
public int hashcode() {
return 2;
}
}
"""
)
);
}

@Test
void doNotRenameWhenSubclassAlreadyDeclaresTarget() {
rewriteRun(
//language=java
java(
"""
class Base {
public int hashcode() {
return 1;
}
}

class Sub extends Base {
@Override
public int hashcode() {
return 2;
}

@Override
public int hashCode() {
return 3;
}
}
"""
)
);
}

@Test
void doNotRenameNonPublicMethod() {
rewriteRun(
//language=java
java(
"""
class Test {
int hashcode() {
return 1;
}

private String tostring() {
return "";
}

protected boolean equal(Object value) {
return false;
}
}
"""
)
);
}

@Test
void doNotRenameStaticMethod() {
rewriteRun(
//language=java
java(
"""
class Test {
public static int hashcode() {
return 1;
}
}
"""
)
);
}

@Test
void renameWhenExistingMethodIsAnOverloadWithDifferentParameters() {
rewriteRun(
//language=java
java(
"""
class Test {
public boolean equal(Object obj) {
return false;
}

public boolean equals(String other) {
return true;
}
}
""",
"""
class Test {
public boolean equals(Object obj) {
return false;
}

public boolean equals(String other) {
return true;
}
}
"""
)
);
}

@Test
void renameUpdatesCallSitesWhenThereIsNoCollision() {
rewriteRun(
//language=java
java(
"""
import java.util.function.Supplier;

class Test {
public String tostring() {
return "";
}

String local() {
return tostring();
}

Supplier<String> reference() {
return this::tostring;
}
}

class Caller {
String call(Test test) {
return test.tostring();
}
}
""",
"""
import java.util.function.Supplier;

class Test {
public String toString() {
return "";
}

String local() {
return toString();
}

Supplier<String> reference() {
return this::toString;
}
}

class Caller {
String call(Test test) {
return test.toString();
}
}
"""
)
);
}
}
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