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ImmutableChecker: start of work to match lambdas.
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PiperOrigin-RevId: 441133187
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@graememorgan
graememorgan authored and Error Prone Team committed Apr 14, 2022
1 parent 006aa1d commit ff2267d
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Showing 3 changed files with 302 additions and 9 deletions.
2 changes: 1 addition & 1 deletion core/src/main/java/com/google/errorprone/bugpatterns/threadsafety/ImmutableAnalysis.java
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Original file line number Diff line number Diff line change
Expand Up @@ -257,7 +257,7 @@ Violation areFieldsImmutable(
}

/** Check a single field for immutability. */
private Violation isFieldImmutable(
Violation isFieldImmutable(
Optional<Tree> tree,
ImmutableSet<String> immutableTyParams,
ClassSymbol classSym,
Expand Down
154 changes: 146 additions & 8 deletions core/src/main/java/com/google/errorprone/bugpatterns/threadsafety/ImmutableChecker.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,10 +19,17 @@
import static com.google.common.collect.ImmutableSet.toImmutableSet;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getReceiver;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.hasAnnotation;
import static java.lang.String.format;
import static java.util.stream.Collectors.joining;

import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;
import com.google.common.collect.Sets.SetView;
import com.google.errorprone.BugPattern;
Expand All @@ -31,6 +38,7 @@
import com.google.errorprone.annotations.Immutable;
import com.google.errorprone.bugpatterns.BugChecker;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.LambdaExpressionTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MemberReferenceTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
Expand All @@ -42,23 +50,34 @@
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.LambdaExpressionTree;
import com.sun.source.tree.MemberReferenceTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.NewClassTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.TypeParameterTree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreePathScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import com.sun.tools.javac.code.Symbol.TypeVariableSymbol;
import com.sun.tools.javac.code.Symbol.VarSymbol;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Type.ClassType;
import com.sun.tools.javac.tree.JCTree.JCMemberReference;
import com.sun.tools.javac.tree.JCTree.JCNewClass;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import javax.lang.model.element.ElementKind;

/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
Expand All @@ -68,13 +87,15 @@
documentSuppression = false)
public class ImmutableChecker extends BugChecker
implements ClassTreeMatcher,
LambdaExpressionTreeMatcher,
NewClassTreeMatcher,
MethodInvocationTreeMatcher,
MethodTreeMatcher,
MemberReferenceTreeMatcher {

private final WellKnownMutability wellKnownMutability;
private final ImmutableSet<String> immutableAnnotations;
private final boolean matchLambdas;

ImmutableChecker(ImmutableSet<String> immutableAnnotations) {
this(ErrorProneFlags.empty(), immutableAnnotations);
Expand All @@ -87,6 +108,125 @@ public ImmutableChecker(ErrorProneFlags flags) {
private ImmutableChecker(ErrorProneFlags flags, ImmutableSet<String> immutableAnnotations) {
this.wellKnownMutability = WellKnownMutability.fromFlags(flags);
this.immutableAnnotations = immutableAnnotations;
this.matchLambdas = flags.getBoolean("ImmutableChecker:MatchLambdas").orElse(true);
}

@Override
public Description matchLambdaExpression(LambdaExpressionTree tree, VisitorState state) {
if (!matchLambdas) {
return NO_MATCH;
}
TypeSymbol lambdaType = getType(tree).tsym;
if (!hasImmutableAnnotation(lambdaType, state)) {
return NO_MATCH;
}
Set<VarSymbol> variablesClosed = new HashSet<>();
SetMultimap<ClassSymbol, MethodSymbol> typesClosed = LinkedHashMultimap.create();
Set<VarSymbol> variablesOwnedByLambda = new HashSet<>();

new TreePathScanner<Void, Void>() {
@Override
public Void visitVariable(VariableTree tree, Void unused) {
var symbol = getSymbol(tree);
variablesOwnedByLambda.add(symbol);
return super.visitVariable(tree, null);
}

@Override
public Void visitMethodInvocation(MethodInvocationTree tree, Void unused) {
if (getReceiver(tree) == null) {
var symbol = getSymbol(tree);
if (!symbol.isStatic()) {
// TODO(b/77333859): This isn't precise. What we really want is the type of `this`, if
// the method call were qualified with it.
typesClosed.put((ClassSymbol) symbol.owner, symbol);
}
}
return super.visitMethodInvocation(tree, null);
}

@Override
public Void visitMemberSelect(MemberSelectTree tree, Void unused) {
// Special case the access of fields to allow accessing fields which would pass an immutable
// check.
if (tree.getExpression() instanceof IdentifierTree
&& getSymbol(tree) instanceof VarSymbol) {
handleIdentifier(getSymbol(tree));
// If we're only seeing a field access, don't complain about the fact we closed around
// `this`.
if (tree.getExpression() instanceof IdentifierTree
&& ((IdentifierTree) tree.getExpression()).getName().contentEquals("this")) {
return null;
}
}
return super.visitMemberSelect(tree, null);
}

@Override
public Void visitIdentifier(IdentifierTree tree, Void unused) {
handleIdentifier(getSymbol(tree));
return super.visitIdentifier(tree, null);
}

private void handleIdentifier(Symbol symbol) {
if (symbol instanceof VarSymbol && !variablesOwnedByLambda.contains(symbol)) {
variablesClosed.add((VarSymbol) symbol);
}
}
}.scan(state.getPath(), null);

ImmutableAnalysis analysis = createImmutableAnalysis(state);
ImmutableSet<String> typarams =
immutableTypeParametersInScope(getSymbol(tree), state, analysis);
variablesClosed.stream()
.map(closedVariable -> checkClosedLambdaVariable(closedVariable, tree, typarams, analysis))
.filter(Violation::isPresent)
.forEachOrdered(
v -> {
String message = formLambdaReason(lambdaType) + ", but " + v.message();
state.reportMatch(buildDescription(tree).setMessage(message).build());
});
for (var entry : typesClosed.asMap().entrySet()) {
var classSymbol = entry.getKey();
var methods = entry.getValue();
if (!hasImmutableAnnotation(classSymbol.type.tsym, state)) {
String message =
format(
"%s, but accesses instance method(s) '%s' on '%s' which is not @Immutable.",
formLambdaReason(lambdaType),
methods.stream().map(Symbol::getSimpleName).collect(joining(", ")),
classSymbol.getSimpleName());
state.reportMatch(buildDescription(tree).setMessage(message).build());
}
}

return NO_MATCH;
}

private Violation checkClosedLambdaVariable(
VarSymbol closedVariable,
LambdaExpressionTree tree,
ImmutableSet<String> typarams,
ImmutableAnalysis analysis) {
if (!closedVariable.getKind().equals(ElementKind.FIELD)) {
return analysis.isThreadSafeType(false, typarams, closedVariable.type);
}
return analysis.isFieldImmutable(
Optional.empty(),
typarams,
(ClassSymbol) closedVariable.owner,
(ClassType) closedVariable.owner.type,
closedVariable,
(t, v) -> buildDescription(tree));
}

private static String formLambdaReason(TypeSymbol typeSymbol) {
return "This lambda implements @Immutable interface '" + typeSymbol.getSimpleName() + "'";
}

private boolean hasImmutableAnnotation(TypeSymbol tsym, VisitorState state) {
return immutableAnnotations.stream()
.anyMatch(annotation -> hasAnnotation(tsym, annotation, state));
}

// check instantiations of `@ImmutableTypeParameter`s in method references
Expand Down Expand Up @@ -203,7 +343,7 @@ public Description matchClass(ClassTree tree, VisitorState state) {
if (!difference.isEmpty()) {
return buildDescription(tree)
.setMessage(
String.format(
format(
"could not find type(s) referenced by containerOf: %s",
Joiner.on("', '").join(difference)))
.build();
Expand All @@ -219,7 +359,7 @@ public Description matchClass(ClassTree tree, VisitorState state) {
if (!immutableAndContainer.isEmpty()) {
return buildDescription(tree)
.setMessage(
String.format(
format(
"using both @ImmutableTypeParameter and containerOf is redundant: %s",
Joiner.on("', '").join(immutableAndContainer)))
.build();
Expand Down Expand Up @@ -276,7 +416,7 @@ private Description.Builder describeClass(
message = "type annotated with @Immutable could not be proven immutable: " + info.message();
} else {
message =
String.format(
format(
"Class extends @Immutable type %s, but is not immutable: %s",
annotation.typeName(), info.message());
}
Expand Down Expand Up @@ -323,7 +463,7 @@ public Description.Builder describe(Tree tree, Violation info) {

private Description.Builder describeAnonymous(Tree tree, Type superType, Violation info) {
String message =
String.format(
format(
"Class extends @Immutable type %s, but is not immutable: %s",
superType, info.message());
return buildDescription(tree).setMessage(message);
Expand All @@ -339,8 +479,7 @@ private Description checkSubtype(ClassTree tree, VisitorState state) {
return NO_MATCH;
}
String message =
String.format(
"Class extends @Immutable type %s, but is not annotated as immutable", superType);
format("Class extends @Immutable type %s, but is not annotated as immutable", superType);
Fix fix =
SuggestedFix.builder()
.prefixWith(tree, "@Immutable ")
Expand All @@ -360,8 +499,7 @@ private Type immutableSupertype(Symbol sym, VisitorState state) {
}
// Don't use getImmutableAnnotation here: subtypes of trusted types are
// also trusted, only check for explicitly annotated supertypes.
if (immutableAnnotations.stream()
.anyMatch(annotation -> ASTHelpers.hasAnnotation(superType.tsym, annotation, state))) {
if (hasImmutableAnnotation(superType.tsym, state)) {
return superType;
}
// We currently trust that @interface annotations are immutable, but don't enforce that
Expand Down
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