Add better type deduction for use-regex-pattern-methods

docs/checks.md

@@ -1872,7 +1872,7 @@ if x is None:
 
 ## FURB170: `use-regex-pattern-methods`
 
-Categories: `readability` `regex`
+Categories: `performance` `readability` `regex`
 
 If you are passing a compiled regular expression to a regex function,
 consider calling the regex method on the pattern itself: It is faster, and

refurb/checks/regex/use_pattern_method.py

@@ -1,8 +1,8 @@
 from dataclasses import dataclass
 
-from mypy.nodes import CallExpr, RefExpr, Var
+from mypy.nodes import CallExpr, RefExpr
 
-from refurb.checks.common import is_same_type
+from refurb.checks.common import get_mypy_type, is_same_type
 from refurb.error import Error
 
 
@@ -36,7 +36,7 @@ class ErrorInfo(Error):
 
     name = "use-regex-pattern-methods"
     code = 170
-    categories = ("readability", "regex")
+    categories = ("performance", "readability", "regex")
 
 
 # This table represents the function calls that we will emit errors for. The
@@ -74,12 +74,8 @@ def check(node: CallExpr, errors: list[Error]) -> None:
             if not arg_format:
                 return
 
-            match pattern:
-                case RefExpr(node=Var(type=ty)) if is_same_type(ty, "re.Pattern"):
-                    pass
-
-                case _:
-                    return
+            if not is_same_type(get_mypy_type(pattern), "re.Pattern"):
+                return
 
             min_len = len([arg for arg in arg_format if arg is ...])
 

test/data/err_170.py

@@ -21,6 +21,11 @@
 
 _ = search(PATTERN, "hello world")
 
+class C:
+    p: re.Pattern
+
+_ = re.sub(C().p, "hello world", "goodbye world")
+
 
 # these should not
 

test/data/err_170.txt

@@ -12,3 +12,4 @@ test/data/err_170.py:18:5 [FURB170]: Replace `re.sub(x, ..., ..., count=...)` wi
 test/data/err_170.py:19:5 [FURB170]: Replace `re.subn(x, ..., ...)` with `x.subn(..., ...)`
 test/data/err_170.py:20:5 [FURB170]: Replace `re.subn(x, ..., ..., count=...)` with `x.subn(..., ..., count=...)`
 test/data/err_170.py:22:5 [FURB170]: Replace `re.search(x, ...)` with `x.search(...)`
+test/data/err_170.py:27:5 [FURB170]: Replace `re.sub(x, ..., ...)` with `x.sub(..., ...)`