code/source: remove support for comparing Source with str

Cross-type comparisons like this are a bad idea. This isn't used.

src/_pytest/_code/source.py

@@ -44,13 +44,10 @@ class Source:
         else:
             self.lines = deindent(getsource(obj).lines)
 
-    def __eq__(self, other):
-        try:
-            return self.lines == other.lines
-        except AttributeError:
-            if isinstance(other, str):
-                return str(self) == other
-            return False
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, Source):
+            return NotImplemented
+        return self.lines == other.lines
 
     # Ignore type because of https://github.com/python/mypy/issues/4266.
     __hash__ = None  # type: ignore

testing/code/test_code.py

@@ -6,6 +6,7 @@ import pytest
 from _pytest._code import Code
 from _pytest._code import ExceptionInfo
 from _pytest._code import Frame
+from _pytest._code import Source
 from _pytest._code.code import ExceptionChainRepr
 from _pytest._code.code import ReprFuncArgs
 
@@ -67,7 +68,7 @@ def test_getstatement_empty_fullsource() -> None:
 
     f = Frame(func())
     with mock.patch.object(f.code.__class__, "fullsource", None):
-        assert f.statement == ""
+        assert f.statement == Source("")
 
 
 def test_code_from_func() -> None:

testing/code/test_source.py

@@ -227,9 +227,9 @@ class TestSourceParsingAndCompiling:
         ''')"""
         )
         s = source.getstatement(0)
-        assert s == str(source)
+        assert s == source
         s = source.getstatement(1)
-        assert s == str(source)
+        assert s == source
 
     def test_getstatementrange_within_constructs(self) -> None:
         source = Source(
@@ -445,7 +445,7 @@ def test_getsource_fallback() -> None:
     expected = """def x():
     pass"""
     src = getsource(x)
-    assert src == expected
+    assert str(src) == expected
 
 
 def test_idem_compile_and_getsource() -> None:
@@ -454,7 +454,7 @@ def test_idem_compile_and_getsource() -> None:
     expected = "def x(): pass"
     co = _pytest._code.compile(expected)
     src = getsource(co)
-    assert src == expected
+    assert str(src) == expected
 
 
 def test_compile_ast() -> None: