"Internal inconsistency" Warning when mixing lambda expressions with bounded wildcards (eclipse-jdt#4892)

* Fixes eclipse-jdt#4891

Author: srikanth-sankaran

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/codegen/BranchLabel.java

@@ -134,8 +134,8 @@ private boolean compatibleOperandStacks(OperandStack stackNow, OperandStack stac
 		return false;
 	int depth = 0;
 	for (int i = 0, size = stackNow.size(); i < size; i++) {
-		TypeBinding tn = stackNow.get(i);
-		TypeBinding te = stackEarlier.get(i);
+		TypeBinding tn = stackNow.get(i).erasure();
+		TypeBinding te = stackEarlier.get(i).erasure();
 		if (TypeBinding.notEquals(tn, te)) {
 			if (!tn.isCompatibleWith(te) && !te.isCompatibleWith(tn)) {
 				if (this.codeStream.classFile.referenceBinding.scope.lowerUpperBound(new TypeBinding[] {te, tn}) == null)

org.eclipse.jdt.core.tests.compiler/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.jdt.core.tests.compiler;singleton:=true
-Bundle-Version: 3.13.1100.qualifier
+Bundle-Version: 3.13.1200.qualifier
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
 Export-Package: org.eclipse.jdt.core.tests.compiler,

org.eclipse.jdt.core.tests.compiler/pom.xml

@@ -19,7 +19,7 @@
     <relativePath>../tests-pom/</relativePath>
   </parent>
   <artifactId>org.eclipse.jdt.core.tests.compiler</artifactId>
-  <version>3.13.1100-SNAPSHOT</version>
+  <version>3.13.1200-SNAPSHOT</version>
   <packaging>eclipse-test-plugin</packaging>
 
   <properties>

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

@@ -7076,5 +7076,47 @@ public static <T> List<?> get(List<T> l) {
         },
         "");
 }
+
+// https://github.com/eclipse-jdt/eclipse.jdt.core/issues/4891
+// "Internal inconsistency" Warning when mixing lambda expressions with bounded wildcards
+public void testIssue4891() {
+	if (this.complianceLevel < ClassFileConstants.JDK22)
+		return;
+
+	Runner runner = new Runner();
+	runner.expectedOutputString =
+			"Compiled and ran fine!";
+	runner.expectedCompilerLog = "";
+
+	runner.testFiles = new String[] {
+		"Bug.java",
+        """
+		import java.util.function.Predicate;
+
+		// Internal inconsistency: Inappropriate operand stack size encountered during translation
+		public class Bug<T>{
+
+			static class Builder<T>{
+				Predicate<? super T> p;
+			}
+
+			final Predicate<? super T> p;
+
+			Bug(Builder<T> builder) {
+				this.p=builder.p==null?_->true:builder.p; //<-- caused by this line
+				// does not happen if passing predicate directly as argument
+				// does not happen without generic bounds <T>
+				// does not happen without ternary expression
+				// does not happen with unbounded wildcard <?>
+			}
+
+			public static void main(String [] args) {
+				System.out.println("Compiled and ran fine!");
+			}
+		}
+         """
+	};
+	runner.runConformTest();
+}
 }