Error when reading txt-file using dart.io - dart

Question

I'm trying to read a file of multiple lines with two digit numbers on each line representing a binary tree structure. I'm using dart and the standard io library. This is the code I'm using:
String contents = new File('./assets/triangle.txt').readAsStringSync();
Problem is I get the following error:
max_path_sum/assets/triangle.txt:1:1: Error: Expected a declaration, but got '75'.
75
^^
max_path_sum/assets/triangle.txt:2:1: Error: Expected a declaration, but got '95'.
95 64
^^
max_path_sum/assets/triangle.txt:2:4: Error: Expected a declaration, but got '64'.
95 64
^^
max_path_sum/assets/triangle.txt:3:1: Error: Expected a declaration, but got '17'.
17 47 82
^^
max_path_sum/assets/triangle.txt:3:4: Error: Expected a declaration, but got '47'.
17 47 82
^^
max_path_sum/assets/triangle.txt:3:7: Error: Expected a declaration, but got '82'.
17 47 82
^^
max_path_sum/assets/triangle.txt:4:1: Error: Expected a declaration, but got '18'.
18 35 87 10
^^
max_path_sum/assets/triangle.txt:4:4: Error: Expected a declaration, but got '35'.
18 35 87 10
^^
max_path_sum/assets/triangle.txt:4:7: Error: Expected a declaration, but got '87'.
18 35 87 10
^^
max_path_sum/assets/triangle.txt:4:10: Error: Expected a declaration, but got '10'.
18 35 87 10
^^
This is the file I'm trying to read:
75
95 64
17 47 82
18 35 87 10
20 04 82 47 65
19 01 23 75 03 34
88 02 77 73 07 63 67
99 65 04 28 06 16 70 92
41 41 26 56 83 40 80 70 33
41 48 72 33 47 32 37 16 94 29
53 71 44 65 25 43 91 52 97 51 14
70 11 33 28 77 73 17 78 39 68 17 57
91 71 52 38 17 14 91 43 58 50 27 29 48
63 66 04 68 89 53 67 30 73 16 69 87 40 31
04 62 98 27 23 09 70 98 73 93 38 53 60 04 23
I've tried different variations of reading the file. Asynchronously, synchronously, line by line, the whole file in one string but keep getting the same error. It obviously reads the lines but seem to expect some other form of input and is not happy with just giving me the data it reads... All examples I find on the web indicate that the code is correct and it should work. So my guess is that I might have to do something with the input file in order for it to be accepted as a valid input but it would seem unpractical since it is able to read the data just fine as it is.
I found the issue. The following formatting of the file works for the first line:
var a = "75";
95 64
17 47 82
18 35 87 10
20 04 82 47 65
19 01 23 75 03 34
88 02 77 73 07 63 67
99 65 04 28 06 16 70 92
41 41 26 56 83 40 80 70 33
41 48 72 33 47 32 37 16 94 29
53 71 44 65 25 43 91 52 97 51 14
70 11 33 28 77 73 17 78 39 68 17 57
91 71 52 38 17 14 91 43 58 50 27 29 48
63 66 04 68 89 53 67 30 73 16 69 87 40 31
04 62 98 27 23 09 70 98 73 93 38 53 60 04 23
So I guess if I make the contents of the file into a string variable it will be fine. But why is this? Isn't it possible to read an ordinary text file in dart without having to change the contents first?

Answer 1

Problem was that I imported the text file using import statement which is probably why dart expected it to be code.