Show version-related syntax errors in the playground (#16419)

## Summary

Fixes part of https://github.com/astral-sh/ruff/issues/16417 by
converting `unsupported_syntax_errors` into playground diagnostics.

## Test Plan

A new `ruff_wasm` test, plus trying out the playground locally:

Default settings:

![image](https://github.com/user-attachments/assets/94377ab5-4d4c-44d3-ae63-fe328a53e083)

`target-version = "py310"`:

![image](https://github.com/user-attachments/assets/51c312ce-70e7-43d3-b6ba-098f2750cb28)

crates/ruff_wasm/src/lib.rs

@@ -18,9 +18,7 @@ use ruff_python_ast::{Mod, PySourceType};
 use ruff_python_codegen::Stylist;
 use ruff_python_formatter::{format_module_ast, pretty_comments, PyFormatContext, QuoteStyle};
 use ruff_python_index::Indexer;
-use ruff_python_parser::{
-    parse, parse_unchecked, parse_unchecked_source, Mode, ParseOptions, Parsed,
-};
+use ruff_python_parser::{parse, parse_unchecked, Mode, ParseOptions, Parsed};
 use ruff_python_trivia::CommentRanges;
 use ruff_source_file::SourceLocation;
 use ruff_text_size::Ranged;
@@ -163,8 +161,14 @@ impl Workspace {
         // TODO(dhruvmanila): Support Jupyter Notebooks
         let source_kind = SourceKind::Python(contents.to_string());
 
+        // Use the unresolved version because we don't have a file path.
+        let target_version = self.settings.linter.unresolved_target_version;
+
         // Parse once.
-        let parsed = parse_unchecked_source(source_kind.source_code(), source_type);
+        let options = ParseOptions::from(source_type).with_target_version(target_version);
+        let parsed = parse_unchecked(source_kind.source_code(), options)
+            .try_into_module()
+            .expect("`PySourceType` always parses to a `ModModule`.");
 
         // Map row and column locations to byte slices (lazily).
         let locator = Locator::new(contents);
@@ -196,7 +200,7 @@ impl Workspace {
             &source_kind,
             source_type,
             &parsed,
-            self.settings.linter.unresolved_target_version,
+            target_version,
         );
 
         let source_code = locator.to_source_code();
@@ -238,6 +242,18 @@ impl Workspace {
                     fix: None,
                 }
             }))
+            .chain(parsed.unsupported_syntax_errors().iter().map(|error| {
+                let start_location = source_code.source_location(error.range.start());
+                let end_location = source_code.source_location(error.range.end());
+
+                ExpandedMessage {
+                    code: None,
+                    message: format!("SyntaxError: {error}"),
+                    location: start_location,
+                    end_location,
+                    fix: None,
+                }
+            }))
             .collect();
 
         serde_wasm_bindgen::to_value(&messages).map_err(into_error)

crates/ruff_wasm/tests/api.rs

@@ -61,6 +61,27 @@ fn syntax_error() {
     );
 }
 
+#[wasm_bindgen_test]
+fn unsupported_syntax_error() {
+    check!(
+        "match 2:\n    case 1: ...",
+        r#"{}"#,
+        [ExpandedMessage {
+            code: None,
+            message: "SyntaxError: Cannot use `match` statement on Python 3.9 (syntax was added in Python 3.10)".to_string(),
+            location: SourceLocation {
+                row: OneIndexed::from_zero_indexed(0),
+                column: OneIndexed::from_zero_indexed(0)
+            },
+            end_location: SourceLocation {
+                row: OneIndexed::from_zero_indexed(0),
+                column: OneIndexed::from_zero_indexed(5)
+            },
+            fix: None,
+        }]
+    );
+}
+
 #[wasm_bindgen_test]
 fn partial_config() {
     check!("if (1, 2):\n    pass", r#"{"ignore": ["F"]}"#, []);