[red-knot] Detect version-related syntax errors (#16379)

## Summary
This PR extends version-related syntax error detection to red-knot. The
main changes here are:

1. Passing `ParseOptions` specifying a `PythonVersion` to parser calls
2. Adding a `python_version` method to the `Db` trait to make this
possible
3. Converting `UnsupportedSyntaxError`s to `Diagnostic`s
4. Updating existing mdtests  to avoid unrelated syntax errors

My initial draft of (1) and (2) in #16090 instead tried passing a
`PythonVersion` down to every parser call, but @MichaReiser suggested
the `Db` approach instead
[here](#16090 (comment)),
and I think it turned out much nicer.

All of the new `python_version` methods look like this:

```rust
fn python_version(&self) -> ruff_python_ast::PythonVersion {
    Program::get(self).python_version(self)
}
```

with the exception of the `TestDb` in `ruff_db`, which hard-codes
`PythonVersion::latest()`.

## Test Plan

Existing mdtests, plus a new mdtest to see at least one of the new
diagnostics.

Author: ntBre

crates/red_knot_ide/src/db.rs

@@ -10,7 +10,7 @@ pub(crate) mod tests {
 
     use super::Db;
     use red_knot_python_semantic::lint::{LintRegistry, RuleSelection};
-    use red_knot_python_semantic::{default_lint_registry, Db as SemanticDb};
+    use red_knot_python_semantic::{default_lint_registry, Db as SemanticDb, Program};
     use ruff_db::files::{File, Files};
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
@@ -83,6 +83,10 @@ pub(crate) mod tests {
         fn files(&self) -> &Files {
             &self.files
         }
+
+        fn python_version(&self) -> ruff_python_ast::PythonVersion {
+            Program::get(self).python_version(self)
+        }
     }
 
     impl Upcast<dyn SourceDb> for TestDb {

crates/red_knot_project/src/db.rs

@@ -149,6 +149,10 @@ impl SourceDb for ProjectDatabase {
     fn files(&self) -> &Files {
         &self.files
     }
+
+    fn python_version(&self) -> ruff_python_ast::PythonVersion {
+        Program::get(self).python_version(self)
+    }
 }
 
 #[salsa::db]
@@ -207,7 +211,7 @@ pub(crate) mod tests {
     use salsa::Event;
 
     use red_knot_python_semantic::lint::{LintRegistry, RuleSelection};
-    use red_knot_python_semantic::Db as SemanticDb;
+    use red_knot_python_semantic::{Db as SemanticDb, Program};
     use ruff_db::files::Files;
     use ruff_db::system::{DbWithTestSystem, System, TestSystem};
     use ruff_db::vendored::VendoredFileSystem;
@@ -281,6 +285,10 @@ pub(crate) mod tests {
         fn files(&self) -> &Files {
             &self.files
         }
+
+        fn python_version(&self) -> ruff_python_ast::PythonVersion {
+            Program::get(self).python_version(self)
+        }
     }
 
     impl Upcast<dyn SemanticDb> for TestDb {

crates/red_knot_project/src/lib.rs

@@ -10,7 +10,8 @@ use red_knot_python_semantic::lint::{LintRegistry, LintRegistryBuilder, RuleSele
 use red_knot_python_semantic::register_lints;
 use red_knot_python_semantic::types::check_types;
 use ruff_db::diagnostic::{
-    create_parse_diagnostic, Annotation, Diagnostic, DiagnosticId, Severity, Span,
+    create_parse_diagnostic, create_unsupported_syntax_diagnostic, Annotation, Diagnostic,
+    DiagnosticId, Severity, Span,
 };
 use ruff_db::files::File;
 use ruff_db::parsed::parsed_module;
@@ -424,6 +425,13 @@ fn check_file_impl(db: &dyn Db, file: File) -> Vec<Diagnostic> {
             .map(|error| create_parse_diagnostic(file, error)),
     );
 
+    diagnostics.extend(
+        parsed
+            .unsupported_syntax_errors()
+            .iter()
+            .map(|error| create_unsupported_syntax_diagnostic(file, error)),
+    );
+
     diagnostics.extend(check_types(db.upcast(), file).into_iter().cloned());
 
     diagnostics.sort_unstable_by_key(|diagnostic| {
@@ -520,18 +528,30 @@ mod tests {
     use crate::db::tests::TestDb;
     use crate::{check_file_impl, ProjectMetadata};
     use red_knot_python_semantic::types::check_types;
+    use red_knot_python_semantic::{Program, ProgramSettings, PythonPlatform, SearchPathSettings};
     use ruff_db::files::system_path_to_file;
     use ruff_db::source::source_text;
     use ruff_db::system::{DbWithTestSystem, DbWithWritableSystem as _, SystemPath, SystemPathBuf};
     use ruff_db::testing::assert_function_query_was_not_run;
     use ruff_python_ast::name::Name;
+    use ruff_python_ast::PythonVersion;
 
     #[test]
     fn check_file_skips_type_checking_when_file_cant_be_read() -> ruff_db::system::Result<()> {
         let project = ProjectMetadata::new(Name::new_static("test"), SystemPathBuf::from("/"));
         let mut db = TestDb::new(project);
         let path = SystemPath::new("test.py");
 
+        Program::from_settings(
+            &db,
+            ProgramSettings {
+                python_version: PythonVersion::default(),
+                python_platform: PythonPlatform::default(),
+                search_paths: SearchPathSettings::new(vec![SystemPathBuf::from(".")]),
+            },
+        )
+        .expect("Failed to configure program settings");
+
         db.write_file(path, "x = 10")?;
         let file = system_path_to_file(&db, path).unwrap();
 

crates/red_knot_python_semantic/resources/mdtest/annotations/callable.md

@@ -237,6 +237,11 @@ def _(c: Callable[[Concatenate[int, str, ...], int], int]):
 
 ## Using `typing.ParamSpec`
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 Using a `ParamSpec` in a `Callable` annotation:
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/annotations/deferred.md

@@ -48,6 +48,11 @@ reveal_type(get_foo())  # revealed: Foo
 
 ## Deferred self-reference annotations in a class definition
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from __future__ import annotations
 
@@ -94,6 +99,11 @@ class Foo:
 
 ## Non-deferred self-reference annotations in a class definition
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 class Foo:
     # error: [unresolved-reference]

crates/red_knot_python_semantic/resources/mdtest/annotations/starred.md

@@ -1,5 +1,10 @@
 # Starred expression annotations
 
+```toml
+[environment]
+python-version = "3.11"
+```
+
 Type annotations for `*args` can be starred expressions themselves:
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/annotations/unsupported_special_forms.md

@@ -79,6 +79,11 @@ reveal_type(F.__mro__)  # revealed: tuple[Literal[F], @Todo(Support for Callable
 
 ## Subscriptability
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 Some of these are not subscriptable:
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md

@@ -25,6 +25,11 @@ x = "foo"  # error: [invalid-assignment] "Object of type `Literal["foo"]` is not
 
 ## Tuple annotations are understood
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 `module.py`:
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/call/function.md

@@ -21,6 +21,11 @@ reveal_type(get_int_async())  # revealed: @Todo(generic types.CoroutineType)
 
 ## Generic
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 def get_int[T]() -> int:
     return 42

crates/red_knot_python_semantic/resources/mdtest/call/methods.md

@@ -399,6 +399,11 @@ reveal_type(getattr_static(C, "f").__get__("dummy", C))  # revealed: bound metho
 
 ### Classmethods mixed with other decorators
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 When a `@classmethod` is additionally decorated with another decorator, it is still treated as a
 class method:
 

crates/red_knot_python_semantic/resources/mdtest/class/super.md

@@ -265,6 +265,11 @@ def f(flag: bool):
 
 ## Supers with Generic Classes
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from knot_extensions import TypeOf, static_assert, is_subtype_of
 
@@ -316,6 +321,11 @@ class A:
 
 ### Failing Condition Checks
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 `super()` requires its first argument to be a valid class, and its second argument to be either an
 instance or a subclass of the first. If either condition is violated, a `TypeError` is raised at
 runtime.

crates/red_knot_python_semantic/resources/mdtest/conditional/match.md

@@ -1,5 +1,10 @@
 # Pattern matching
 
+```toml
+[environment]
+python-version = "3.10"
+```
+
 ## With wildcard
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/dataclasses.md

@@ -297,6 +297,11 @@ reveal_type(WithoutEq(1) == WithoutEq(2))  # revealed: bool
 
 ### `order`
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 `order` is set to `False` by default. If `order=True`, `__lt__`, `__le__`, `__gt__`, and `__ge__`
 methods will be generated:
 
@@ -471,6 +476,11 @@ reveal_type(C.__init__)  # revealed: (x: int = Literal[15], y: int = Literal[0],
 
 ## Generic dataclasses
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from dataclasses import dataclass
 

crates/red_knot_python_semantic/resources/mdtest/diagnostics/version_related_syntax_errors.md

@@ -0,0 +1,37 @@
+# Version-related syntax error diagnostics
+
+## `match` statement
+
+The `match` statement was introduced in Python 3.10.
+
+### Before 3.10
+
+<!-- snapshot-diagnostics -->
+
+We should emit a syntax error before 3.10.
+
+```toml
+[environment]
+python-version = "3.9"
+```
+
+```py
+match 2:  # error: 1 [invalid-syntax] "Cannot use `match` statement on Python 3.9 (syntax was added in Python 3.10)"
+    case 1:
+        print("it's one")
+```
+
+### After 3.10
+
+On or after 3.10, no error should be reported.
+
+```toml
+[environment]
+python-version = "3.10"
+```
+
+```py
+match 2:
+    case 1:
+        print("it's one")
+```

crates/red_knot_python_semantic/resources/mdtest/directives/assert_never.md

@@ -26,6 +26,11 @@ def _(never: Never, any_: Any, unknown: Unknown, flag: bool):
 
 ## Use case: Type narrowing and exhaustiveness checking
 
+```toml
+[environment]
+python-version = "3.10"
+```
+
 `assert_never` can be used in combination with type narrowing as a way to make sure that all cases
 are handled in a series of `isinstance` checks or other narrowing patterns that are supported.
 

crates/red_knot_python_semantic/resources/mdtest/function/parameters.md

@@ -76,6 +76,11 @@ def g(x: Any = "foo"):
 
 ## Stub functions
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ### In Protocol
 
 ```py

crates/red_knot_python_semantic/resources/mdtest/function/return_type.md

@@ -56,6 +56,11 @@ def f() -> int:
 
 ### In Protocol
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from typing import Protocol, TypeVar
 
@@ -85,6 +90,11 @@ class Lorem(t[0]):
 
 ### In abstract method
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ```py
 from abc import ABC, abstractmethod
 

crates/red_knot_python_semantic/resources/mdtest/generics/classes.md

@@ -1,5 +1,10 @@
 # Generic classes
 
+```toml
+[environment]
+python-version = "3.13"
+```
+
 ## PEP 695 syntax
 
 TODO: Add a `red_knot_extension` function that asserts whether a function or class is generic.

crates/red_knot_python_semantic/resources/mdtest/generics/functions.md

@@ -1,5 +1,10 @@
 # Generic functions
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 ## Typevar must be used at least twice
 
 If you're only using a typevar for a single parameter, you don't need the typevar — just use

crates/red_knot_python_semantic/resources/mdtest/generics/pep695.md

@@ -1,5 +1,10 @@
 # PEP 695 Generics
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 [PEP 695] and Python 3.12 introduced new, more ergonomic syntax for type variables.
 
 ## Type variables

crates/red_knot_python_semantic/resources/mdtest/generics/scoping.md

@@ -1,5 +1,10 @@
 # Scoping rules for type variables
 
+```toml
+[environment]
+python-version = "3.12"
+```
+
 Most of these tests come from the [Scoping rules for type variables][scoping] section of the typing
 spec.