WIP

Author: AlexWaygood

crates/ruff/tests/lint.rs

@@ -2568,6 +2568,46 @@ fn a005_module_shadowing_strict_default() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn walrus_before_py38() {
+    // ok
+    assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+        .args(STDIN_BASE_OPTIONS)
+        .args(["--stdin-filename", "test.py"])
+        .arg("--target-version=py38")
+        .arg("-")
+        .pass_stdin(r#"if x := 1: pass"#),
+        @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    test.py:1:10: E701 Multiple statements on one line (colon)
+    Found 1 error.
+
+    ----- stderr -----
+    "
+    );
+
+    // not ok on 3.7
+    assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+        .args(STDIN_BASE_OPTIONS)
+        .args(["--stdin-filename", "test.py"])
+        .arg("--target-version=py37")
+        .arg("-")
+        .pass_stdin(r#"if x := 1: pass"#),
+        @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+    test.py:1:4: SyntaxError: Cannot use named assignment expression (`:=`) on Python 3.7 (syntax was new in Python 3.8)
+    test.py:1:10: E701 Multiple statements on one line (colon)
+    Found 2 errors.
+
+    ----- stderr -----
+    "
+    );
+}
+
 #[test]
 fn match_before_py310() {
     assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))

crates/ruff_linter/src/message/mod.rs

@@ -16,7 +16,7 @@ pub use pylint::PylintEmitter;
 pub use rdjson::RdjsonEmitter;
 use ruff_diagnostics::{Diagnostic, DiagnosticKind, Fix};
 use ruff_notebook::NotebookIndex;
-use ruff_python_parser::{ParseError, SyntaxError, SyntaxErrorKind};
+use ruff_python_parser::{ParseError, SyntaxError};
 use ruff_source_file::{SourceFile, SourceLocation};
 use ruff_text_size::{Ranged, TextLen, TextRange, TextSize};
 pub use sarif::SarifEmitter;
@@ -123,13 +123,11 @@ impl Message {
 
     /// Create a [`Message`] from the given [`SyntaxError`].
     pub fn from_syntax_error(syntax_error: &SyntaxError, file: SourceFile) -> Message {
-        match syntax_error.kind {
-            SyntaxErrorKind::MatchBeforePy310 => Message::SyntaxError(SyntaxErrorMessage {
-                message: format!("SyntaxError: {}", syntax_error.message()),
-                range: syntax_error.range,
-                file,
-            }),
-        }
+        Message::SyntaxError(SyntaxErrorMessage {
+            message: format!("SyntaxError: {}", syntax_error.message()),
+            range: syntax_error.range,
+            file,
+        })
     }
 
     pub const fn as_diagnostic_message(&self) -> Option<&DiagnosticMessage> {

crates/ruff_python_parser/src/error.rs

@@ -437,30 +437,36 @@ pub struct SyntaxError {
 impl SyntaxError {
     pub fn message(&self) -> String {
         match self.kind {
+            SyntaxErrorKind::WalrusBeforePy38 => format!(
+                "Cannot use named assignment expression (`:=`) on Python {} (syntax was new in Python 3.8)",
+                self.target_version
+            ),
             SyntaxErrorKind::MatchBeforePy310 => format!(
-                "Cannot use `match` statement on Python {major}.{minor} (syntax was new in Python 3.10)",
-                major = self.target_version.major,
-                minor = self.target_version.minor,
+                "Cannot use `match` statement on Python {} (syntax was new in Python 3.10)",
+                self.target_version,
             ),
         }
     }
 
     /// The earliest allowed version for the syntax associated with this error.
     pub const fn version(&self) -> PythonVersion {
         match self.kind {
+            SyntaxErrorKind::WalrusBeforePy38 => PythonVersion::PY38,
             SyntaxErrorKind::MatchBeforePy310 => PythonVersion::PY310,
         }
     }
 }
 
 #[derive(Debug, PartialEq, Clone, Copy)]
 pub enum SyntaxErrorKind {
+    WalrusBeforePy38,
     MatchBeforePy310,
 }
 
 impl SyntaxErrorKind {
     pub const fn as_str(self) -> &'static str {
         match self {
+            SyntaxErrorKind::WalrusBeforePy38 => "walrus-before-python-38",
             SyntaxErrorKind::MatchBeforePy310 => "match-before-python-310",
         }
     }

crates/ruff_python_parser/src/parser/expression.rs

@@ -7,7 +7,7 @@ use rustc_hash::{FxBuildHasher, FxHashSet};
 use ruff_python_ast::name::Name;
 use ruff_python_ast::{
     self as ast, BoolOp, CmpOp, ConversionFlag, Expr, ExprContext, FStringElement, FStringElements,
-    IpyEscapeKind, Number, Operator, StringFlags, UnaryOp,
+    IpyEscapeKind, Number, Operator, PythonVersion, StringFlags, UnaryOp,
 };
 use ruff_text_size::{Ranged, TextLen, TextRange, TextSize};
 
@@ -16,7 +16,7 @@ use crate::parser::{helpers, FunctionKind, Parser};
 use crate::string::{parse_fstring_literal_element, parse_string_literal, StringType};
 use crate::token::{TokenKind, TokenValue};
 use crate::token_set::TokenSet;
-use crate::{FStringErrorType, Mode, ParseErrorType};
+use crate::{FStringErrorType, Mode, ParseErrorType, SyntaxError, SyntaxErrorKind};
 
 use super::{FStringElementsKind, Parenthesized, RecoveryContextKind};
 
@@ -2161,10 +2161,20 @@ impl<'src> Parser<'src> {
 
         let value = self.parse_conditional_expression_or_higher();
 
+        let range = self.node_range(start);
+
+        if self.options.target_version < PythonVersion::PY38 {
+            self.syntax_errors.push(SyntaxError {
+                kind: SyntaxErrorKind::WalrusBeforePy38,
+                range,
+                target_version: self.options.target_version,
+            });
+        }
+
         ast::ExprNamed {
             target: Box::new(target),
             value: Box::new(value.expr),
-            range: self.node_range(start),
+            range,
         }
     }
 

crates/ruff_python_parser/src/parser/statement.rs

@@ -1458,13 +1458,22 @@ impl<'src> Parser<'src> {
             );
         }
 
+        let range = self.node_range(try_start);
+        if is_star && self.options.target_version < PythonVersion::PY311 {
+            self.syntax_errors.push(SyntaxError {
+                kind: SyntaxErrorKind::ExceptStarBeforePy311,
+                range,
+                target_version: self.options.target_version,
+            });
+        }
+
         ast::StmtTry {
             body: try_body,
             handlers,
             orelse,
             finalbody,
             is_star,
-            range: self.node_range(try_start),
+            range,
         }
     }