Do not check for unchecked conversion if target is not parameterized (eclipse-jdt#4286)

Reduce risk of the error
  The type X cannot be resolved. It is indirectly referenced from ...
Do so by early exit from TypeBinding.needsUncheckedConversion() before findSuperTypeOriginatingFrom(..) could trigger lookup of more types. If leaf targetType is not parameterized, then the answer is known to be `false`.

Fix eclipse-jdt#4231

Author: laeubi

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

@@ -1557,7 +1557,7 @@ public boolean needsUncheckedConversion(TypeBinding targetType) {
 	if (TypeBinding.equalsEquals(this, targetType))
 		return false;
 	targetType = targetType.leafComponentType();
-	if (!(targetType instanceof ReferenceBinding))
+	if (!(targetType instanceof ParameterizedTypeBinding))
 		return false;
 
 	TypeBinding currentType = leafComponentType();

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

@@ -10142,4 +10142,50 @@ void test() {
 			"Void methods cannot return a value\n" +
 			"----------\n");
 }
+
+public void testMissingClass_return() {
+	Runner runner = new Runner();
+	runner.testFiles = new String[] {
+			"p1/I.java",
+			"""
+			package p1;
+			public class I {}
+			""",
+			"p2/P.java",
+			"""
+			package p2;
+			import p1.I;
+			public class P extends I {
+				public P(Number n) {}
+			}
+			"""
+		};
+	runner.runConformTest();
+
+	// delete binary file I (i.e. simulate removing it from classpath for subsequent compile)
+	Util.delete(new File(OUTPUT_DIR, "p1" + File.separator + "I.class"));
+
+	runner.shouldFlushOutputDirectory = false;
+	runner.testFiles = new String[] {
+			"p3/C.java",
+			"""
+			package p3;
+			import p2.P;
+			class C {
+				public Object test() {
+					return new P(1);
+				}
+
+				public Object test2() {
+					Object o = new P(1);
+					return o;
+				}
+
+			}
+			"""
+		};
+	runner.expectedCompilerLog = "";
+	runner.runConformTest();
+}
+
 }