Record type inference fails when 'var' and <> mixed

Fixes eclipse-jdt#1361

Author: mpalat

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/lookup/InferenceContext18.java

@@ -1149,48 +1149,52 @@ public boolean reduceAndIncorporate(ConstraintFormula constraint) throws Inferen
 				final int numVars = variableSet.size();
 				if (numVars > 0) {
 					final InferenceVariable[] variables = variableSet.toArray(new InferenceVariable[numVars]);
-					variables: if (!isRecordPatternTypeInference && !tmpBoundSet.hasCaptureBound(variableSet)) {
+					variables: if (!tmpBoundSet.hasCaptureBound(variableSet)) {
 						// try to instantiate this set of variables in a fresh copy of the bound set:
 						BoundSet prevBoundSet = tmpBoundSet;
 						tmpBoundSet = tmpBoundSet.copy();
 						for (int j = 0; j < variables.length; j++) {
 							InferenceVariable variable = variables[j];
-							// try lower bounds:
-							TypeBinding[] lowerBounds = tmpBoundSet.lowerBounds(variable, true/*onlyProper*/);
-							if (lowerBounds != Binding.NO_TYPES) {
-								TypeBinding lub = this.scope.lowerUpperBound(lowerBounds);
-								if (lub == TypeBinding.VOID || lub == null)
-									return null;
-								tmpBoundSet.addBound(new TypeBound(variable, lub, ReductionResult.SAME), this.environment);
+							if (isRecordPatternTypeInference) {
+								tmpBoundSet.addBound(new TypeBound(variable, this.object, ReductionResult.SAME), this.environment);
 							} else {
-								TypeBinding[] upperBounds = tmpBoundSet.upperBounds(variable, true/*onlyProper*/);
-								// check exception bounds:
-								if (tmpBoundSet.inThrows.contains(variable.prototype()) && tmpBoundSet.hasOnlyTrivialExceptionBounds(variable, upperBounds)) {
-									TypeBinding runtimeException = this.scope.getType(TypeConstants.JAVA_LANG_RUNTIMEEXCEPTION, 3);
-									tmpBoundSet.addBound(new TypeBound(variable, runtimeException, ReductionResult.SAME), this.environment);
+								// try lower bounds:
+								TypeBinding[] lowerBounds = tmpBoundSet.lowerBounds(variable, true/*onlyProper*/);
+								if (lowerBounds != Binding.NO_TYPES) {
+									TypeBinding lub = this.scope.lowerUpperBound(lowerBounds);
+									if (lub == TypeBinding.VOID || lub == null)
+										return null;
+									tmpBoundSet.addBound(new TypeBound(variable, lub, ReductionResult.SAME), this.environment);
 								} else {
-									// try upper bounds:
-									TypeBinding glb = this.object;
-									if (upperBounds != Binding.NO_TYPES) {
-										if (upperBounds.length == 1) {
-											glb = upperBounds[0];
-										} else {
-											TypeBinding[] glbs = Scope.greaterLowerBound(upperBounds, this.scope, this.environment);
-											if (glbs == null) {
-												return null;
-											} else if (glbs.length == 1) {
-												glb = glbs[0];
+									TypeBinding[] upperBounds = tmpBoundSet.upperBounds(variable, true/*onlyProper*/);
+									// check exception bounds:
+									if (tmpBoundSet.inThrows.contains(variable.prototype()) && tmpBoundSet.hasOnlyTrivialExceptionBounds(variable, upperBounds)) {
+										TypeBinding runtimeException = this.scope.getType(TypeConstants.JAVA_LANG_RUNTIMEEXCEPTION, 3);
+										tmpBoundSet.addBound(new TypeBound(variable, runtimeException, ReductionResult.SAME), this.environment);
+									} else {
+										// try upper bounds:
+										TypeBinding glb = this.object;
+										if (upperBounds != Binding.NO_TYPES) {
+											if (upperBounds.length == 1) {
+												glb = upperBounds[0];
 											} else {
-												glb = intersectionFromGlb(glbs);
-												if (glb == null) {
-													// inconsistent intersection
-													tmpBoundSet = prevBoundSet; // clean up
-													break variables; // and start over
+												TypeBinding[] glbs = Scope.greaterLowerBound(upperBounds, this.scope, this.environment);
+												if (glbs == null) {
+													return null;
+												} else if (glbs.length == 1) {
+													glb = glbs[0];
+												} else {
+													glb = intersectionFromGlb(glbs);
+													if (glb == null) {
+														// inconsistent intersection
+														tmpBoundSet = prevBoundSet; // clean up
+														break variables; // and start over
+													}
 												}
 											}
 										}
+										tmpBoundSet.addBound(new TypeBound(variable, glb, ReductionResult.SAME), this.environment);
 									}
-									tmpBoundSet.addBound(new TypeBound(variable, glb, ReductionResult.SAME), this.environment);
 								}
 							}
 						}

org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/RecordPatternTest.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2022, 2023 IBM Corporation and others.
+ * Copyright (c) 2022, 2025 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -28,7 +28,7 @@ public class RecordPatternTest extends AbstractRegressionTest9 {
 	static {
 //		TESTS_NUMBERS = new int [] { 40 };
 //		TESTS_RANGE = new int[] { 1, -1 };
-//		TESTS_NAMES = new String[] { "testRecordTypeInfer_4643" };
+//		TESTS_NAMES = new String[] { "testRecordPatternTypeInference_001" };
 	}
 	private String extraLibPath;
 	public static Class<?> testClass() {
@@ -5089,5 +5089,25 @@ public static void main(String[] args) {
 			"Record component with type Integer is not compatible with type String\n" +
 			"----------\n");
 	}
+	public void testRecordTypeInfer_1361_001() {
+		runConformTest(new String[] { "X.java",
+		"""
+		record Record<T>(T a) {}
+		public class X {
+			static void test(Object o) {
+				if (o instanceof Record(var x)) {
+					var v = new Record<>(x);
+					Record<Object> r = v;
+					System.out.println(true);
+				}
+			}
+			public static void main(String[] args) {
+				Record<Integer> r = new Record<>(10);
+				test(r);
+			}
+		}
+		""" },
+		"true");
+	}
 
 }