Keep pure: char_string, char_string_range, maybe.

Add test for `elemental` `move`.

Author: zoziha

doc/specs/stdlib_string_type.md

@@ -528,7 +528,7 @@ Return the character sequence represented by the string.
 
 #### Class
 
-Elemental function.
+Pure function.
 
 #### Argument
 
@@ -618,7 +618,7 @@ Return a substring from the character sequence of the string.
 
 #### Class
 
-Elemental function.
+Pure function.
 
 #### Argument
 

src/stdlib_string_type.fypp

@@ -438,7 +438,7 @@ contains
 
 
     !> Return the character sequence represented by the string.
-    elemental function char_string(string) result(character_string)
+    pure function char_string(string) result(character_string)
         type(string_type), intent(in) :: string
         character(len=len(string)) :: character_string
 
@@ -457,7 +457,7 @@ contains
     end function char_string_pos
 
     !> Return the character sequence represented by the string.
-    elemental function char_string_range(string, start, last) result(character_string)
+    pure function char_string_range(string, start, last) result(character_string)
         type(string_type), intent(in) :: string
         integer, intent(in) :: start
         integer, intent(in) :: last
@@ -1233,7 +1233,7 @@ contains
 
 
     !> Safely return the character sequences represented by the string
-    elemental function maybe(string) result(maybe_string)
+    pure function maybe(string) result(maybe_string)
         type(string_type), intent(in) :: string
         character(len=len(string)) :: maybe_string
         if (allocated(string%raw)) then

src/tests/string/test_string_intrinsic.f90

@@ -667,9 +667,11 @@ subroutine test_move(error)
         !> Error handling
         type(error_type), allocatable, intent(out) :: error
         type(string_type) :: from_string, to_string
+        type(string_type) :: from_strings(2), to_strings(2)
         character(len=:), allocatable :: from_char, to_char
 
         from_string = "Move This String"
+        from_strings = "Move This String"
         from_char = "Move This Char"
         call check(error, from_string == "Move This String" .and. to_string == "" .and. &
             & from_char == "Move This Char" .and. .not. allocated(to_char), &
@@ -713,7 +715,11 @@ subroutine test_move(error)
         ! string_type (allocated) --> string_type (allocated)
         call move(from_string, from_string)
         call check(error, from_string == "", "move: test_case 8")
-
+        if (allocated(error)) return
+        
+        ! elemental: string_type (allocated) --> string_type (not allocated)
+        call move(from_strings, to_strings)
+        call check(error, all(from_strings(:) == "") .and. all(to_strings(:) == "Move This String"), "move: test_case 9")
     end subroutine test_move
 
 end module test_string_intrinsic