[llvm] [utils][filecheck-lint]: speedup filecheck_lint (PR #94191)

[Benjamin Chetioui via llvm-commits]

================
@@ -78,32 +78,41 @@ def levenshtein(s1: str, s2: str) -> int:  # pylint: disable=g-doc-args
 
 
 class FileRange:
-    """Stores the coordinates of a span on a single line within a file.
+    """Derives the coordinates of a span on a single line within a file.
 
     Attributes:
-      line:         the line number
-      start_column: the (inclusive) column where the span starts
-      end_column:   the (inclusive) column where the span ends
+      content:      line str
+      start_byte: the (inclusive) byte offset the span starts
+      end_byte:   the (inclusive) byte offset the span ends
     """
 
-    line: int
-    start_column: int
-    end_column: int
+    content: str
+    start_byte: int
+    end_byte: int
 
     def __init__(
         self, content: str, start_byte: int, end_byte: int
     ):  # pylint: disable=g-doc-args
-        """Derives a span's coordinates based on a string and start/end bytes.
-
+        """
         `start_byte` and `end_byte` are assumed to be on the same line.
         """
-        content_before_span = content[:start_byte]
-        self.line = content_before_span.count("\n") + 1
-        self.start_column = start_byte - content_before_span.rfind("\n")
-        self.end_column = self.start_column + (end_byte - start_byte - 1)
+        self.content = content
+        self.start_byte = start_byte
+        self.end_byte = end_byte
 
-    def __str__(self) -> str:
-        return f"{self.line}:{self.start_column}-{self.end_column}"
+    def as_str(self):
+        """
+        Derives span from line and coordinates
+
+        start_column: the (inclusive) column where the span starts
+        end_column:   the (inclusive) column where the span ends
+        """
+        content_before_span = self.content[: self.start_byte]
----------------
bchetioui wrote:

Please remove unnecessary space before `self.start_byte`. (See [PEP8](https://peps.python.org/pep-0008/) documentation about slice notation.)

https://github.com/llvm/llvm-project/pull/94191