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Skip declaration-site variance for invariant storage #1007

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69 changes: 68 additions & 1 deletion src/main/java/org/openrewrite/staticanalysis/DeclarationSiteTypeVariance.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@

import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;

import static java.util.stream.Collectors.toList;
import static org.openrewrite.java.tree.J.Wildcard.Bound.Extends;
Expand Down Expand Up @@ -95,7 +96,7 @@ public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method, Ex
if (varParam.getTypeExpression() instanceof J.ParameterizedType) {
J.ParameterizedType pt = (J.ParameterizedType) varParam.getTypeExpression();
for (VariantTypeSpec variantTypeSpec : variantTypeSpecs) {
if (variantTypeSpec.hasType(pt)) {
if (variantTypeSpec.hasType(pt) && !isStoredInvariantly(m, varParam)) {
return varParam.withTypeExpression(useDeclarationSiteVariance(pt, variantTypeSpec));
}
}
Expand All @@ -106,6 +107,72 @@ public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method, Ex
}));
}

private boolean isStoredInvariantly(J.MethodDeclaration method, J.VariableDeclarations parameter) {
if (method.getBody() == null || parameter.getVariables().size() != 1) {
return false;
}
JavaType.Variable parameterType = parameter.getVariables().get(0).getVariableType();
if (parameterType == null) {
return false;
}
return new JavaIsoVisitor<AtomicBoolean>() {
@Override
public J.Assignment visitAssignment(J.Assignment assignment, AtomicBoolean stored) {
J.Assignment visitedAssignment = super.visitAssignment(assignment, stored);
if (TypeUtils.isOfType(visitedAssignment.getVariable().getType(), parameterType.getType()) &&
!references(visitedAssignment.getVariable(), parameterType) &&
directlyReferences(visitedAssignment.getAssignment(), parameterType)) {
stored.set(true);
}
return visitedAssignment;
}

@Override
public J.VariableDeclarations.NamedVariable visitVariable(
J.VariableDeclarations.NamedVariable variable, AtomicBoolean stored) {
J.VariableDeclarations.NamedVariable visitedVariable = super.visitVariable(variable, stored);
J.VariableDeclarations declarations = getCursor().firstEnclosing(J.VariableDeclarations.class);
boolean explicitlyTyped = declarations != null &&
!(declarations.getTypeExpression() instanceof J.Identifier &&
"var".equals(((J.Identifier) declarations.getTypeExpression()).getSimpleName()));
if (explicitlyTyped && visitedVariable.getInitializer() != null &&
TypeUtils.isOfType(visitedVariable.getType(), parameterType.getType()) &&
directlyReferences(visitedVariable.getInitializer(), parameterType)) {
stored.set(true);
}
return visitedVariable;
}
}.reduce(method.getBody(), new AtomicBoolean()).get();
}

private boolean references(Expression expression, JavaType.Variable parameterType) {
return new JavaIsoVisitor<AtomicBoolean>() {
@Override
public J.Lambda visitLambda(J.Lambda lambda, AtomicBoolean found) {
return lambda;
}

@Override
public J.MemberReference visitMemberReference(J.MemberReference memberRef, AtomicBoolean found) {
return memberRef;
}

@Override
public J.Identifier visitIdentifier(J.Identifier identifier, AtomicBoolean found) {
if (parameterType.equals(identifier.getFieldType())) {
found.set(true);
}
return identifier;
}
}.reduce(expression, new AtomicBoolean()).get();
}

private boolean directlyReferences(Expression expression, JavaType.Variable parameterType) {
Expression unwrapped = expression.unwrap();
return unwrapped instanceof J.Identifier &&
parameterType.equals(((J.Identifier) unwrapped).getFieldType());
}

private J.ParameterizedType useDeclarationSiteVariance(J.ParameterizedType pt, VariantTypeSpec spec) {
return pt.withTypeParameters(ListUtils.map(pt.getTypeParameters(), (i, tp) -> {
VariantTypeSpec.Variance variance = spec.getVariances().get(i);
Expand Down
216 changes: 216 additions & 0 deletions src/test/java/org/openrewrite/staticanalysis/DeclarationSiteTypeVarianceTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -235,4 +235,220 @@ public void test(Function<In, Out> f) {
)
);
}
@Test
void doesNotAddVarianceToParameterStoredInvariantly() {
rewriteRun(
//language=java
java(
"""
import java.util.function.Function;

class FieldTest<Input, Output> {
private final Function<Input, Output> mapper;

FieldTest(Function<Input, Output> mapper) {
this.mapper = mapper;
}
}
"""
),
//language=java
java(
"""
import java.util.function.Function;

class LocalTest<Input, Output> {
void test(Function<Input, Output> mapper) {
Function<Input, Output> stored = mapper;
}
}
"""
)
);
}

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

class Test<Input, Output> {
private final Function<? super Input, ? extends Output> mapper;

Test(Function<Input, Output> mapper) {
this.mapper = mapper;
}
}
""",
"""
import java.util.function.Function;

class Test<Input, Output> {
private final Function<? super Input, ? extends Output> mapper;

Test(Function<? super Input, ? extends Output> mapper) {
this.mapper = mapper;
}
}
"""
)
);
}

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

class Test<Input, Output> {
private Function<Input, Output> mapper;

void set(Function<Input, Output> mapper) {
this.mapper = input -> mapper.apply(input);
}

void forward(Function<Input, Output> mapper) {
set(mapper);
}
}
""",
"""
import java.util.function.Function;

class Test<Input, Output> {
private Function<Input, Output> mapper;

void set(Function<? super Input, ? extends Output> mapper) {
this.mapper = input -> mapper.apply(input);
}

void forward(Function<? super Input, ? extends Output> mapper) {
set(mapper);
}
}
"""
)
);
}

@Test
void addsVarianceWhenParameterIsNormalizedInPlace() {
rewriteRun(
//language=java
java(
"""
import java.util.Objects;
import java.util.function.Function;

class Test<Input, Output> {
void use(Function<Input, Output> mapper) {
mapper = Objects.requireNonNull(mapper);
}

void forward(Function<Input, Output> mapper) {
use(mapper);
}
}
""",
"""
import java.util.Objects;
import java.util.function.Function;

class Test<Input, Output> {
void use(Function<? super Input, ? extends Output> mapper) {
mapper = Objects.requireNonNull(mapper);
}

void forward(Function<? super Input, ? extends Output> mapper) {
use(mapper);
}
}
"""
)
);
}

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

class Test<Input, Output> {
void use(Function<Input, Output> mapper) {
var stored = mapper;
}

void forward(Function<Input, Output> mapper) {
use(mapper);
}
}
""",
"""
import java.util.function.Function;

class Test<Input, Output> {
void use(Function<? super Input, ? extends Output> mapper) {
var stored = mapper;
}

void forward(Function<? super Input, ? extends Output> mapper) {
use(mapper);
}
}
"""
)
);
}

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

class Test<Input, Output> {
Function<Input, Output> adapt(Function<? super Input, ? extends Output> mapper) {
return input -> mapper.apply(input);
}

void use(Function<Input, Output> mapper) {
Function<Input, Output> stored = adapt(mapper);
}

void forward(Function<Input, Output> mapper) {
use(mapper);
}
}
""",
"""
import java.util.function.Function;

class Test<Input, Output> {
Function<Input, Output> adapt(Function<? super Input, ? extends Output> mapper) {
return input -> mapper.apply(input);
}

void use(Function<? super Input, ? extends Output> mapper) {
Function<Input, Output> stored = adapt(mapper);
}

void forward(Function<? super Input, ? extends Output> mapper) {
use(mapper);
}
}
"""
)
);
}
}
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