[Java 25] Bogus error: The blank final field o may not have been initialized (#4435)

Improved solution:
* Fix cases were additionally a prologue exists
* Clarify boundaries between PROLOGUE this() and REST

Fixes #4416

---------

Co-authored-by: Srikanth Sankaran <[email protected]>

Author: stephan-herrmann

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/ConstructorDeclaration.java

@@ -89,9 +89,11 @@ public void analyseCode(ClassScope classScope, InitializationFlowContext initial
 public void analyseCode(ClassScope classScope, InitializationFlowContext initializerFlowContext, FlowInfo flowInfo, int initialReachMode, AnalysisMode mode) {
 	// Effect of 'AnalysisMode mode':
 	// ALL: 		analyse in one go as normal.
-	// PROLOGUE:	analyse only statements *before* the explicit constructor call (if any)
-	// REST:		analyse only starting with the explicit constructor call, if none present behaves like ALL
+	// PROLOGUE:	analyse only statements up-to the explicit constructor call (arguments of this call are technically prologue, too)
+	//              if no relevant prologue exists, this invocation does nothing, and due to prologueInfo==null the next invocation will use mode ALL
+	// REST:		analyse only statements after the explicit constructor call
 	// FlowContext and FlowInfo produced during PROLOGUE will be held in fields prologueContext and prologueInfo for use during REST
+	// prologueInfo is furthermore assumed to happen *before* any field initializers, see its use in TypeDeclaration.internalAnalyseCode()
 	if (this.ignoreFurtherInvestigation)
 		return;
 
@@ -111,16 +113,6 @@ public void analyseCode(ClassScope classScope, InitializationFlowContext initial
 			constructorContext = this.prologueContext;
 			flowInfo = this.prologueInfo.addInitializationsFrom(flowInfo);
 			// skip the part already done during PROLOGUE analysis ...
-			if (this.constructorCall != null) {
-				if (this.constructorCall.accessMode == ExplicitConstructorCall.This) {
-					FieldBinding[] fields = this.binding.declaringClass.fields();
-					for (FieldBinding field : fields) {
-						if (!field.isStatic()) {
-							flowInfo.markAsDefinitelyAssigned(field);
-						}
-					}
-				}
-			}
 		} else {
 			flowInfo.setReachMode(initialReachMode);
 
@@ -223,20 +215,16 @@ public void analyseCode(ClassScope classScope, InitializationFlowContext initial
 			// propagate to constructor call
 			if (this.constructorCall != null) {
 				flowInfo = this.constructorCall.analyseCode(this.scope, constructorContext, flowInfo);
-				if (mode == AnalysisMode.PROLOGUE && hasArgumentNeedingAnalysis)
-					this.prologueInfo = flowInfo.copy();
-				// if calling 'this(...)', then flag all non-static fields as definitely
-				// set since they are supposed to be set inside other local constructor
-				if (this.constructorCall.accessMode == ExplicitConstructorCall.This) {
-					FieldBinding[] fields = this.binding.declaringClass.fields();
-					for (FieldBinding field : fields) {
-						if (!field.isStatic()) {
-							flowInfo.markAsDefinitelyAssigned(field);
-						}
-					}
+				if (mode == AnalysisMode.PROLOGUE) {
+					if (hasArgumentNeedingAnalysis)
+						this.prologueInfo = flowInfo.copy();
+					return;
 				}
 			}
 		}
+		if (this.constructorCall != null && mode != AnalysisMode.PROLOGUE) {
+			markFieldsAsInitializedAfterThisCall(this.constructorCall, flowInfo);
+		}
 		// reuse the reachMode from non static field info
 		flowInfo.setReachMode(nonStaticFieldInfoReachMode);
 
@@ -247,8 +235,10 @@ public void analyseCode(ClassScope classScope, InitializationFlowContext initial
 			int complaintLevel = (nonStaticFieldInfoReachMode & FlowInfo.UNREACHABLE) == 0 ? Statement.NOT_COMPLAINED : Statement.COMPLAINED_FAKE_REACHABLE;
 			for (Statement stat : this.statements) {
 				if (mode == AnalysisMode.REST && lateConstructorCall != null) {
-					if (stat == lateConstructorCall)	// if true this is where we start analysing
+					if (stat == lateConstructorCall) {	// if true this is where we start analysing
+						markFieldsAsInitializedAfterThisCall(lateConstructorCall, flowInfo);
 						lateConstructorCall = null; 	// no more checking for subsequent statements
+					}
 					continue;							// skip statements already processed during PROLOGUE analysis
 				}
 				if ((complaintLevel = stat.complainIfUnreachable(flowInfo, this.scope, complaintLevel, true)) < Statement.COMPLAINED_UNREACHABLE) {
@@ -265,9 +255,8 @@ public void analyseCode(ClassScope classScope, InitializationFlowContext initial
 				}
 			}
 			if (mode == AnalysisMode.PROLOGUE) {
-				if (this.prologueInfo == null)		// don't overwrite info stored in the context of this.constructorCall
-					this.prologueInfo = flowInfo;	// keep for second iteration, also signals the need for REST analysis
-				return;								// we're done for this time
+				this.prologueInfo = flowInfo;	// keep for second iteration, also signals the need for REST analysis
+				return;							// we're done for this time
 			}
 		}
 	// check for missing returning path
@@ -305,6 +294,19 @@ public void analyseCode(ClassScope classScope, InitializationFlowContext initial
 	}
 }
 
+private void markFieldsAsInitializedAfterThisCall(ExplicitConstructorCall call, FlowInfo flowInfo) {
+	if (call.accessMode == ExplicitConstructorCall.This) {
+		// if calling 'this(...)', then flag all non-static fields as definitely
+		// set since they are supposed to be set inside other local constructor
+		FieldBinding[] fields = this.binding.declaringClass.fields();
+		for (FieldBinding field : fields) {
+			if (!field.isStatic()) {
+				flowInfo.markAsDefinitelyAssigned(field);
+			}
+		}
+	}
+}
+
 @Override
 public AbstractVariableDeclaration[] arguments(boolean includedElided) {
 	return includedElided && this.isCompactConstructor() ? this.protoArguments : super.arguments(includedElided);

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

@@ -513,6 +513,29 @@ public WrongNotInitialized() {
 			"""
 	});
 }
+public void testIssue4416_withPrologue() {
+	if (this.complianceLevel < ClassFileConstants.JDK25)
+		return; // uses flexible constructor bodies
+	runConformTest(new String[] {
+			"WrongNotInitialized.java",
+			"""
+			public class WrongNotInitialized {
+			  private final Object o;
+
+			  public WrongNotInitialized(final Object o) {
+			    super();
+			    this.o = o;
+			  }
+
+			  public WrongNotInitialized() {
+			    System.out.println();
+			    this(new Object());
+			    System.out.println(o.toString());
+			  }
+			}
+			"""
+	});
+}
 // https://github.com/eclipse-jdt/eclipse.jdt.core/issues/4416
 // Bogus error: The blank final field o may not have been initialized
 public void testIssue4416b() {
@@ -537,6 +560,31 @@ public class Test {
 			"""
 	});
 }
+public void testIssue4416b_withPrologue() {
+	if (this.complianceLevel < ClassFileConstants.JDK25)
+		return; // uses flexible constructor bodies
+	runConformTest(new String[] {
+			"Test.java",
+			"""
+			public class Test {
+
+				final int x;
+
+				Test(int x) {
+					this.x = x;
+				}
+
+				Test(Test a) {
+					System.out.println();
+					this(a.x);
+					//this(1);
+
+					System.out.println(x);
+				}
+			}
+			"""
+	});
+}
 // https://github.com/eclipse-jdt/eclipse.jdt.core/issues/4416
 // Bogus error: The blank final field o may not have been initialized
 public void testIssue4416c() {
@@ -556,6 +604,24 @@ public TestRecord(int b)
 			"""
 	});
 }
+public void testIssue4416c_withPrologue() {
+	if (this.complianceLevel < ClassFileConstants.JDK25)
+		return; // uses flexible constructor bodies
+	runConformTest(new String[] {
+			"TestRecord.java",
+			"""
+			public record TestRecord(String a)
+			{
+			    public TestRecord(int b)
+			    {
+			        System.out.println();
+			        this(String.valueOf(b));
+			        System.out.println(a.length());
+			    }
+			}
+			"""
+	});
+}
 // https://github.com/eclipse-jdt/eclipse.jdt.core/issues/4416
 // Bogus error: The blank final field o may not have been initialized
 public void testIssue4416d() {
@@ -578,6 +644,31 @@ public class Test {
 			"""
 	});
 }
+//https://github.com/eclipse-jdt/eclipse.jdt.core/issues/4416
+//Bogus error: The blank final field o may not have been initialized
+public void testIssue4416d_withPrologue() {
+	if (this.complianceLevel < ClassFileConstants.JDK25)
+		return; // uses flexible constructor bodies
+	runConformTest(new String[] {
+			"Test.java",
+			"""
+			public class Test {
+
+			        private final Object r;
+
+			        Test() {
+			        		System.out.println();
+			                this(Integer.valueOf(1));
+			                r.hashCode();
+			        }
+
+			        Test(Object r) {
+			                this.r = r;
+			        }
+			}
+			"""
+	});
+}
 public static Class testClass() {
 	return InitializationTests.class;
 }