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Implement unconditional patterns. #2647

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Merged
copybara-service merged 1 commit into from
Jan 13, 2026
+26 −13
Merged

Implement unconditional patterns. #2647

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33 changes: 24 additions & 9 deletions translator/src/main/java/com/google/devtools/j2objc/translate/InstanceOfPatternRewriter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,8 @@ public void endVisit(InstanceofExpression node) {

List<VariableElement> variablesToDeclare = new ArrayList<>();
Expression condition =
computePatternCondition(expression, node.getPattern(), variablesToDeclare);
computePatternCondition(
expression, node.getPattern(), /* allowUnconditional= */ false, variablesToDeclare);

for (var variableToDeclare : variablesToDeclare) {
// Initialize the patternVariables to null. The implementation of patterns in switches creates
Expand All @@ -124,7 +125,10 @@ public void endVisit(InstanceofExpression node) {
}

private Expression computePatternCondition(
Expression expression, Pattern pattern, List<VariableElement> variablesToDeclare) {
Expression expression,
Pattern pattern,
boolean allowUnconditional,
List<VariableElement> variablesToDeclare) {
switch (pattern) {
case BindingPattern bindingPattern -> {
VariableElement patternVariable = bindingPattern.getVariable().getVariableElement();
Expand All @@ -137,9 +141,12 @@ private Expression computePatternCondition(
.setTypeMirror(typeUtil.getBoolean());
}

boolean isUnconditional = allowUnconditional
&& typeUtil.isAssignable(
expression.getTypeMirror(), patternVariable.asType());

Expression instanceofLhs = expression.copy();
if (!(expression instanceof SimpleName)
&& !patternVariable.asType().getKind().isPrimitive()) {
if (!(expression instanceof SimpleName) && !isUnconditional) {
// Use a temporary variable to avoid evaluating the expression more than once and make
// sure that user written property getters that might have side-effects are only
// evaluated once.
Expand All @@ -154,9 +161,9 @@ private Expression computePatternCondition(
variablesToDeclare.add(patternVariable);
// expression instanceof T && (patternVariable = (T) expression, true)
return andCondition(
patternVariable.asType().getKind().isPrimitive()
// Primitives don't needs any checking. In the future when/if primitive patterns are
// incorporated in the Java language, this should be updated.
isUnconditional
// Unconditional patterns don't needs any checking. In the future when/if primitive
// patterns are incorporated in the Java language, this should be updated.
? null
: new InstanceofExpression()
.setLeftOperand(instanceofLhs)
Expand All @@ -178,7 +185,13 @@ private Expression computePatternCondition(
// (e instanceof Rec rec)
Expression condition =
computePatternCondition(
expression, new BindingPattern(tempVariable), variablesToDeclare);
expression,
new BindingPattern(tempVariable),
// The binding pattern resulting from the implementation of a deconstruction pattern
// cannot be uncondiional since its components will be accessed and hence it cannot
// allow nulls.
/* allowUnconditional */ false,
variablesToDeclare);

var recordType = (TypeElement) ((ClassType) deconstructionPattern.getTypeMirror()).tsym;
for (int i = 0; i < deconstructionPattern.getNestedPatterns().size(); i++) {
Expand All @@ -198,7 +211,9 @@ private Expression computePatternCondition(

condition =
andCondition(
condition, computePatternCondition(property, nestedPattern, variablesToDeclare));
condition,
computePatternCondition(
property, nestedPattern, /* allowUnconditional= */ true, variablesToDeclare));
}
return condition;
}
Expand Down
6 changes: 2 additions & 4 deletions ...tor/src/test/java/com/google/devtools/j2objc/translate/InstanceOfPatternRewriterTest.java
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Expand Up @@ -191,18 +191,16 @@ void test() {
id comp = nil;
Test_A *rec_1 = nil;
int32_t i1 = 0;
NSString *comp_1 = nil;
NSString *s = nil;
int32_t i2 = 0;
Test_A *comp_2 = nil;
Test_A *a = nil;
id o = create_Test_B_initWithId_withInt_withTest_A_(create_Test_A_initWithInt_withNSString_(1, @""), 3, create_Test_A_initWithInt_withNSString_(2, @"bye"));
if ([o isKindOfClass:[Test_B class]] && (rec = (Test_B *) o, true)\
&& [comp = [((Test_B *) nil_chk(rec)) a1] isKindOfClass:[Test_A class]] && (rec_1 = (Test_A *) comp, true)\
&& (i1 = (int32_t) [((Test_A *) nil_chk(rec_1)) i], true)\
&& [comp_1 = [((Test_A *) nil_chk(rec_1)) s] isKindOfClass:[NSString class]] && (s = comp_1, true)\
&& (s = [((Test_A *) nil_chk(rec_1)) s], true)\
&& (i2 = (int32_t) [((Test_B *) nil_chk(rec)) i], true)\
&& [comp_2 = [((Test_B *) nil_chk(rec)) a2] isKindOfClass:[Test_A class]] && (a = comp_2, true)) {
&& (a = [((Test_B *) nil_chk(rec)) a2], true)) {
""");
}
}