Since JDK-8222852 the default String concat strategy aggressively folds string constants into prepender method handles, which means an expression like foo + bar and one like "x" + foo + "y" + bar + "z" will have similar shape, but take slightly different paths through generated code. This could mean slightly reduced code coverage in tests like String/concat/ImplicitStringConcatShapes. Consider extending this test to explicitly include surrounding String constants, which should cover more cases and put a bit more stress on the implementation strategy.