If a hex literal has an 'd' of 'f' in it, such as '0xf' or '0xd', the compiler fails with illegal tree structure.

The other hex literals work.  The issue is probably related to using `f` and `d` in float and double literals.

```
    public void testHexCollisionDouble() {
        assertEquals(13, exec("return 0xd"));
    }

    public void testHexCollisionFloat() {
        assertEquals(15, exec("return 0xf"));
    }

    public void testHex() throws Exception {
        for (int i = 0; i <= 15; i++) {
            String hex = Integer.toHexString(i);
            if ("d".equals(hex) || "f".equals(hex)) {
                continue;
            }
            assertEquals(i, exec("return 0x" + hex));
            assertEquals(i, exec("return 0x" + hex.toUpperCase(Locale.ROOT)));
            assertEquals(i, exec("return 0X" + hex));
            assertEquals(i, exec("return 0X" + hex.toUpperCase(Locale.ROOT)));
        }
    }
```
modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultSemanticAnalysisPhase.java
}
        SBlock userBlockNode = userLambdaNode.getBlockNode();
        if (userBlockNode.getStatementNodes().isEmpty()) {
            throw userLambdaNode.createError(new IllegalArgumentException("cannot generate empty lambda"));
        }
        semanticScope.setCondition(userBlockNode, LastSource.class);
        visit(userBlockNode, lambdaScope);
        if (lambdaScope.usesInstanceMethod()) {
            semanticScope.setCondition(userLambdaNode, InstanceCapturingLambda.class);
        }
        if (semanticScope.getCondition(userBlockNode, MethodEscape.class) == false) {
            throw userLambdaNode.createError(new IllegalArgumentException("not all paths return a value for lambda"));
        }
        
        List<Variable> capturedVariables = new ArrayList<>(lambdaScope.getCaptures());
        List<Class<?>> typeParametersWithCaptures = new ArrayList<>(capturedVariables.size() + typeParameters.size());
        List<String> parameterNamesWithCaptures = new ArrayList<>(capturedVariables.size() + parameterNames.size());
        for (Variable capturedVariable : capturedVariables) {
            typeParametersWithCaptures.add(capturedVariable.type());
            parameterNamesWithCaptures.add(capturedVariable.name());
        }
        typeParametersWithCaptures.addAll(typeParameters);
        parameterNamesWithCaptures.addAll(parameterNames);
        
        String name = scriptScope.getNextSyntheticName("lambda");
        boolean isStatic = lambdaScope.usesInstanceMethod() == false;
        scriptScope.getFunctionTable().addFunction(name, returnType, typeParametersWithCaptures, true, isStatic);
        Class<?> valueType;
        
        if (targetType == null) {