source: avoid printing source file twice if it is the same for beginning and end (which is very likely).

compiler/source.py

@@ -17,10 +17,16 @@ class Location:
     file: str = "<none>"
     internal: bool = False
 
+    def to_string(self, show_file: bool = True) -> str:
+        filename = "<internal>" if self.internal else self.file
+        message = ""
+        if show_file:
+            message = f"{filename}:"
+        message += f"{self.line}:{self.character}"
+        return message
+
     def __str__(self) -> str:
-        if self.internal:
-            return "<internal>"
-        return f"{self.file}:{self.line}:{self.character}"
+        return self.to_string()
 
     @typecheck
     def __lt__(self, other: Location) -> bool:
@@ -76,7 +82,7 @@ class SourceLocation:
     def __str__(self):
         if self.begin == self.end:
             return str(self.begin)
-        return f"{str(self.begin)} - {str(self.end)}"
+        return f"{str(self.begin)} - {self.end.to_string(self.begin.file != self.end.file)}"
 
     @typecheck
     def __lt__(self, other: SourceLocation) -> bool: