From 937a3dbefcf549b571e45e4a32081437ad55b49f Mon Sep 17 00:00:00 2001
From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Fri, 8 Jul 2022 16:16:40 -0700
Subject: [PATCH 1/6] Add failing regression test

---
 Lib/test/test_compile.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index ab1685d3e5b8a9..cc80dad01a6c6c 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -1181,6 +1181,26 @@ def test_complex_single_line_expression(self):
         self.assertOpcodeSourcePositionIs(compiled_code, 'BINARY_OP',
             line=1, end_line=1, column=0, end_column=27, occurrence=4)
 
+    def test_multiline_assert_rewritten_as_method_call(self):
+        # GH-94694
+        tree = ast.parse("assert (\n42\n)")
+        old_node = tree.body[0]
+        new_node = ast.Expr(
+            ast.Call(
+                ast.Attribute(
+                    ast.Name("spam", ast.Load()),
+                    "eggs",
+                    ast.Load(),
+                ),
+                [],
+                [],
+            )
+        )
+        ast.copy_location(new_node, old_node)
+        ast.fix_missing_locations(new_node)
+        tree.body[0] = new_node
+        compile(tree, "<test>", "exec")
+
 
 class TestExpressionStackSize(unittest.TestCase):
     # These tests check that the computed stack size for a code object

From dd5a39195c2159afa4868ddbee06ed4e482b44a6 Mon Sep 17 00:00:00 2001
From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Fri, 8 Jul 2022 16:16:54 -0700
Subject: [PATCH 2/6] Fix invalid column math

---
 Python/compile.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Python/compile.c b/Python/compile.c
index f36a6e85a54c20..f6afc00400be06 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -4737,7 +4737,19 @@ update_location_to_match_attr(struct compiler *c, expr_ty meth)
     if (meth->lineno != meth->end_lineno) {
         // Make start location match attribute
         c->u->u_loc.lineno = meth->end_lineno;
-        c->u->u_loc.col_offset = meth->end_col_offset - (int)PyUnicode_GetLength(meth->v.Attribute.attr)-1;
+        int len = (int)PyUnicode_GET_LENGTH(meth->v.Attribute.attr);
+        // The dot may or not be on this line. Don't try to include it in the
+        // column span, it's more trouble than it's worth:
+        if (len <= meth->end_col_offset) {
+            //        |---- end_col_offset
+            // .method(...)
+            //  |---------- new col_offset
+            c->u->u_loc.col_offset = meth->end_col_offset - len;
+        }
+        else {
+            // GH-94694: Somebody's compiling weird ASTs. Just drop the columns:
+            c->u->u_loc.col_offset = c->u->u_loc.end_col_offset = -1;
+        }
     }
 }
 

From ffd3413fe84c2900095c7eae366d8c7da2edffe2 Mon Sep 17 00:00:00 2001
From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Fri, 8 Jul 2022 16:35:44 -0700
Subject: [PATCH 3/6] Add additional tests for column locations

---
 Lib/test/test_traceback.py | 51 ++++++++++++++++++++++++++++++++++++++
 Python/compile.c           |  2 +-
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index 722c265a6a8a51..72d67bf6ef1407 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -702,6 +702,57 @@ class A: pass
         )
         self.assertEqual(result_lines, expected_error.splitlines())
 
+    def test_multiline_method_call_a(self):
+        def f():
+            (None
+                .method
+            )()
+        actual = self.get_exception(f)
+        expected = [
+            f"Traceback (most recent call last):",
+            f"  File \"{__file__}\", line {self.callable_line}, in get_exception",
+            f"    callable()",
+            f"    ^^^^^^^^^^",
+            f"  File \"{__file__}\", line {f.__code__.co_firstlineno + 2}, in f",
+            f"    .method",
+            f"     ^^^^^^",
+        ]
+        self.assertEqual(actual, expected)
+
+    def test_multiline_method_call_b(self):
+        def f():
+            (None.
+                method
+            )()
+        actual = self.get_exception(f)
+        expected = [
+            f"Traceback (most recent call last):",
+            f"  File \"{__file__}\", line {self.callable_line}, in get_exception",
+            f"    callable()",
+            f"    ^^^^^^^^^^",
+            f"  File \"{__file__}\", line {f.__code__.co_firstlineno + 2}, in f",
+            f"    method",
+            f"    ^^^^^^",
+        ]
+        self.assertEqual(actual, expected)
+
+    def test_multiline_method_call_c(self):
+        def f():
+            (None
+                . method
+            )()
+        actual = self.get_exception(f)
+        expected = [
+            f"Traceback (most recent call last):",
+            f"  File \"{__file__}\", line {self.callable_line}, in get_exception",
+            f"    callable()",
+            f"    ^^^^^^^^^^",
+            f"  File \"{__file__}\", line {f.__code__.co_firstlineno + 2}, in f",
+            f"    . method",
+            f"      ^^^^^^",
+        ]
+        self.assertEqual(actual, expected)
+
 @cpython_only
 @requires_debug_ranges()
 class CPythonTracebackErrorCaretTests(TracebackErrorLocationCaretTests):
diff --git a/Python/compile.c b/Python/compile.c
index f6afc00400be06..fd93aa1d57dd50 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -4738,7 +4738,7 @@ update_location_to_match_attr(struct compiler *c, expr_ty meth)
         // Make start location match attribute
         c->u->u_loc.lineno = meth->end_lineno;
         int len = (int)PyUnicode_GET_LENGTH(meth->v.Attribute.attr);
-        // The dot may or not be on this line. Don't try to include it in the
+        // We have no idea where the dot is. Don't try to include it in the
         // column span, it's more trouble than it's worth:
         if (len <= meth->end_col_offset) {
             //        |---- end_col_offset

From 53ba4445a038e3430b1f6609c167f973c943699d Mon Sep 17 00:00:00 2001
From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Fri, 8 Jul 2022 16:48:53 -0700
Subject: [PATCH 4/6] blurb add

---
 .../2022-07-08-16-44-11.gh-issue-94694.VkL2CM.rst             | 4 ++++
 1 file changed, 4 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2022-07-08-16-44-11.gh-issue-94694.VkL2CM.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-08-16-44-11.gh-issue-94694.VkL2CM.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-08-16-44-11.gh-issue-94694.VkL2CM.rst
new file mode 100644
index 00000000000000..6434788140f420
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-07-08-16-44-11.gh-issue-94694.VkL2CM.rst	
@@ -0,0 +1,4 @@
+Fix an issue that could cause code with multi-line method lookups to have
+misleading or incorrect column offset information. In some cases (when
+compiling a hand-built AST) this could have resulted in a hard crash of the
+interpreter.

From 33dc4d8a911512fa310dc262b1c641f26c89cc9d Mon Sep 17 00:00:00 2001
From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Fri, 8 Jul 2022 16:49:01 -0700
Subject: [PATCH 5/6] Update comment

---
 Lib/test/test_compile.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index cc80dad01a6c6c..3887a87c6e073d 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -1182,7 +1182,8 @@ def test_complex_single_line_expression(self):
             line=1, end_line=1, column=0, end_column=27, occurrence=4)
 
     def test_multiline_assert_rewritten_as_method_call(self):
-        # GH-94694
+        # GH-94694: Copying location information from a "real" node to a
+        # handwritten one should always be valid!
         tree = ast.parse("assert (\n42\n)")
         old_node = tree.body[0]
         new_node = ast.Expr(

From 13c07ff7f39a51803872a3d07eacc473bce68f78 Mon Sep 17 00:00:00 2001
From: Brandt Bucher <brandtbucher@microsoft.com>
Date: Sat, 9 Jul 2022 16:00:42 -0700
Subject: [PATCH 6/6] Feedback from code review

---
 Lib/test/test_compile.py | 4 ++--
 Python/compile.c         | 7 +------
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index 3887a87c6e073d..bc022a9f5cbe71 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -1182,8 +1182,8 @@ def test_complex_single_line_expression(self):
             line=1, end_line=1, column=0, end_column=27, occurrence=4)
 
     def test_multiline_assert_rewritten_as_method_call(self):
-        # GH-94694: Copying location information from a "real" node to a
-        # handwritten one should always be valid!
+        # GH-94694: Don't crash if pytest rewrites a multiline assert as a
+        # method call with the same location information:
         tree = ast.parse("assert (\n42\n)")
         old_node = tree.body[0]
         new_node = ast.Expr(
diff --git a/Python/compile.c b/Python/compile.c
index fd93aa1d57dd50..427fb2a369481f 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -4736,14 +4736,9 @@ update_location_to_match_attr(struct compiler *c, expr_ty meth)
 {
     if (meth->lineno != meth->end_lineno) {
         // Make start location match attribute
-        c->u->u_loc.lineno = meth->end_lineno;
+        c->u->u_loc.lineno = c->u->u_loc.end_lineno = meth->end_lineno;
         int len = (int)PyUnicode_GET_LENGTH(meth->v.Attribute.attr);
-        // We have no idea where the dot is. Don't try to include it in the
-        // column span, it's more trouble than it's worth:
         if (len <= meth->end_col_offset) {
-            //        |---- end_col_offset
-            // .method(...)
-            //  |---------- new col_offset
             c->u->u_loc.col_offset = meth->end_col_offset - len;
         }
         else {

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