Fix convert to lambda method reference to recognize a lambda parm (#2153)

* Fix convert to lambda method reference to recognize invalid condition

- modify ConvertLambdaToMethodReferenceFixCore to recognize when a
  method invocation in the lambda body is inside a static method call and
  the method invocation itself is non-static in an interface
- add new test to AssistQuickFixTest1d8
- fixes #2152

Author: jjohnstn

org.eclipse.jdt.core.manipulation/core extension/org/eclipse/jdt/internal/corext/fix/ConvertLambdaToMethodReferenceFixCore.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2023, 2024 IBM Corporation and others.
+ * Copyright (c) 2023, 2025 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -216,11 +216,37 @@ public static boolean representsDefiningNode(ASTNode innerNode, ASTNode defining
 	}
 
 	public static boolean isValidLambdaReferenceToMethod(Expression expression) {
-		return expression instanceof ClassInstanceCreation
+		if (expression instanceof ClassInstanceCreation
 				|| expression instanceof ArrayCreation
 				|| expression instanceof SuperMethodInvocation
-				|| expression instanceof MethodInvocation
-				|| expression instanceof InstanceofExpression;
+				|| expression instanceof InstanceofExpression) {
+			return true;
+		}
+		if (expression instanceof MethodInvocation methodInvocation) {
+			// Bug546645 - prevent bad code when there is a lambda method invocation body
+			// inside a static method invocation where the lambda method invocation is non-static
+			// in an interface (can't make a non-static method reference to the interface and
+			// can't instantiate the interface via new to reference it)
+			LambdaExpression lambda= ASTNodes.getFirstAncestorOrNull(expression, LambdaExpression.class);
+			if (lambda != null) {
+				MethodInvocation outer= ASTNodes.getFirstAncestorOrNull(lambda, MethodInvocation.class);
+				if (outer == null) {
+					return true;
+				}
+				IMethodBinding outerBinding= outer.resolveMethodBinding();
+				if (!Modifier.isStatic(outerBinding.getModifiers())) {
+					return true;
+				}
+				IMethodBinding methodBinding= methodInvocation.resolveMethodBinding();
+				if (methodBinding != null) {
+					ITypeBinding typeBinding= methodBinding.getDeclaringClass();
+					if (typeBinding != null) {
+						return !typeBinding.isInterface() || Modifier.isStatic(methodBinding.getModifiers());
+					}
+				}
+			}
+		}
+		return false;
 	}
 
 	private static class ConvertLambdaToMethodReferenceProposalOperation extends CompilationUnitRewriteOperation {

org.eclipse.jdt.ui.tests/ui/org/eclipse/jdt/ui/tests/quickfix/AssistQuickFixTest1d8.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2013, 2024 IBM Corporation and others.
+ * Copyright (c) 2013, 2025 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -5038,6 +5038,35 @@ public boolean foo() {
 		assertExpectedExistInProposals(proposals, new String[] { expected1 });
 	}
 
+	@Test
+	public void testConvertLambdaToMethodReference7() throws Exception {
+		IPackageFragment pack1= fSourceFolder.createPackageFragment("test1", false, null);
+		String str= """
+			package test1;
+			import java.util.function.Function;
+
+			public class E7 {
+				 public static void main(String[] args) {
+				     f(s -> s.m(s));
+				 }
+
+				 static void f(Function<X, X> f) {}
+
+				 interface X {
+				     X m(X x);
+				 }
+			}
+			""";
+		ICompilationUnit cu= pack1.createCompilationUnit("E7.java", str, false, null);
+
+		int offset= str.indexOf("s ->");
+		AssistContext context= getCorrectionContext(cu, offset, 4);
+		assertNoErrors(context);
+		List<IJavaCompletionProposal> proposals= collectAssists(context, false);
+		assertCorrectLabels(proposals);
+		assertProposalDoesNotExist(proposals, CorrectionMessages.QuickAssistProcessor_convert_to_method_reference);
+	}
+
 	@Test
 	public void testIssue1520() throws Exception {
 		IPackageFragment pack1= fSourceFolder.createPackageFragment("test1", false, null);