Merge pull request #543 from Carltoffel/fix-string-concat

Fix string concat

Author: milancurcic

src/stdlib_string_type.fypp

@@ -1082,7 +1082,7 @@ contains
  type(string_type), intent(in) :: rhs
  type(string_type) :: string
 
- string%raw = maybe(rhs) // maybe(lhs)
+ string%raw = maybe(lhs) // maybe(rhs)
 
  end function concat_string_string
 

src/tests/string/test_string_operator.f90

@@ -99,11 +99,15 @@ subroutine test_ne
  end subroutine test_ne
 
  subroutine test_concat
- type(string_type) :: string
-
- string = "Hello, "
- string = string // "World!"
- call check(len(string) == 13)
+ type(string_type) :: a, b
+
+ a = "a"
+ b = "b"
+ call check( "a" // b == "ab" )
+ call check( a // "b" == "ab" )
+ call check( a // b == "ab" )
+ call check( a // "" == "a" )
+ call check( "" // b == "b" )
  end subroutine test_concat
 
 end module test_string_operator