Case-sensitive matching

One possibly surprising rule of matching is that lowercase identifiers in the case clause always have a value bound to them but if the identifier starts with an uppercase character the identifier is used as a value to match against.

1. scala> val iWantToMatch = 10
2. iWantToMatch: Int = 10
4. scala> val iDontWantToMatch = 1
5. iDontWantToMatch: Int = 1
7. scala> 10 match {
8.      | case iDontWantToMatch => "boo"
9.      | case iWantToMatch => "yay"
10.      | }
11. :7: error: unreachable code
12.        case iWantToMatch => "yay"
13.                             ^
15. // we have an error because iDontWantToMatch is treated as a parameter to the iDontWantToMatch => "boo" function.
16. // Not as a value to match against.
18. // in this example you can see how iDontWantToMatch is has 10 bound to it
20. scala> 10 match {
21.      | case iDontWantToMatch => iDontWantToMatch
22.      | }
23. res9: Int = 10
25. // back tick forces the value to be matched against
26. scala> 10 match {
27.      | case `iDontWantToMatch` => "boo"
28.      | case `iWantToMatch` => "yay"
29.      | }
30. res7: java.lang.String = yay
32. scala> val IWantToMatch = 10
33. IWantToMatch: Int = 10
35. scala> val IDontWantToMatch = 1
36. IDontWantToMatch: Int = 1
38. // also if first character is upper case it is matched against.
39. scala> 10 match {
40.      | case IDontWantToMatch => "boo"
41.      | case IWantToMatch => "yay"
42.      | }
43. res8: java.lang.String = yay