From f8c20258aec5148029da904fe1ea91c1c8f1be50 Mon Sep 17 00:00:00 2001
From: David Peter <sharkdp@users.noreply.github.com>
Date: Tue, 19 Nov 2024 10:04:51 +0100
Subject: [PATCH] [red-knot] Do not panic on f-string format spec expressions
 (#14436)

## Summary

Previously, we panicked on expressions like `f"{v:{f'0.2f'}}"` because
we did not infer types for expressions nested inside format spec
elements.

## Test Plan

```
cargo nextest run -p red_knot_workspace -- --ignored linter_af linter_gz
```
---
 crates/red_knot_python_semantic/src/types/infer.rs          | 6 ++++++
 .../resources/test/corpus/94_strformat_conversion.py        | 3 +++
 crates/red_knot_workspace/tests/check.rs                    | 2 --
 3 files changed, 9 insertions(+), 2 deletions(-)
 create mode 100644 crates/red_knot_workspace/resources/test/corpus/94_strformat_conversion.py

diff --git a/crates/red_knot_python_semantic/src/types/infer.rs b/crates/red_knot_python_semantic/src/types/infer.rs
index 1b33798a96..b6e8a76a07 100644
--- a/crates/red_knot_python_semantic/src/types/infer.rs
+++ b/crates/red_knot_python_semantic/src/types/infer.rs
@@ -2285,6 +2285,12 @@ impl<'db> TypeInferenceBuilder<'db> {
                                 } = expression;
                                 let ty = self.infer_expression(expression);
 
+                                if let Some(ref format_spec) = format_spec {
+                                    for element in format_spec.elements.expressions() {
+                                        self.infer_expression(&element.expression);
+                                    }
+                                }
+
                                 // TODO: handle format specifiers by calling a method
                                 // (`Type::format`?) that handles the `__format__` method.
                                 // Conversion flags should be handled before calling `__format__`.
diff --git a/crates/red_knot_workspace/resources/test/corpus/94_strformat_conversion.py b/crates/red_knot_workspace/resources/test/corpus/94_strformat_conversion.py
new file mode 100644
index 0000000000..adf563cf77
--- /dev/null
+++ b/crates/red_knot_workspace/resources/test/corpus/94_strformat_conversion.py
@@ -0,0 +1,3 @@
+msg = "hello"
+
+f"{msg!r:>{10+10}}"
diff --git a/crates/red_knot_workspace/tests/check.rs b/crates/red_knot_workspace/tests/check.rs
index 8aae30b261..0a2ad2f426 100644
--- a/crates/red_knot_workspace/tests/check.rs
+++ b/crates/red_knot_workspace/tests/check.rs
@@ -283,9 +283,7 @@ const KNOWN_FAILURES: &[(&str, bool, bool)] = &[
     ("crates/ruff_linter/resources/test/fixtures/pyflakes/F821_20.py", true, true),
     ("crates/ruff_linter/resources/test/fixtures/pyflakes/F821_26.py", true, false),
     // Fails for unknown reasons:
-    ("crates/ruff_linter/resources/test/fixtures/pyflakes/F541.py", true, true),
     ("crates/ruff_linter/resources/test/fixtures/pyflakes/F632.py", true, true),
     ("crates/ruff_linter/resources/test/fixtures/pyflakes/F811_19.py", true, false),
     ("crates/ruff_linter/resources/test/fixtures/pyupgrade/UP039.py", true, false),
-    ("crates/ruff_python_parser/resources/valid/expressions/f_string.py", true, true),
 ];