[syntax-errors] Make async-comprehension-in-sync-comprehension more specific (#17460)

## Summary

While adding semantic error support to red-knot, I noticed duplicate
diagnostics for code like this:

```py
# error: [invalid-syntax] "cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.9 (syntax was added in 3.11)"
# error: [invalid-syntax] "`asynchronous comprehension` outside of an asynchronous function"
 [reveal_type(x) async for x in AsyncIterable()]
```

Beyond the duplication, the first error message doesn't make much sense
because this syntax is _not_ allowed on Python 3.11 either.

To fix this, this PR renames the
`async-comprehension-outside-async-function` semantic syntax error to
`async-comprehension-in-sync-comprehension` and fixes the rule to avoid
applying outside of sync comprehensions at all.

## Test Plan

New linter test demonstrating the false positive. The mdtests from my red-knot 
PR also reflect this change.

Author: ntBre

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

@@ -19,7 +19,7 @@ async def elements(n):
     yield n
 
 async def f():
-    # error: 19 [invalid-syntax] "cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)"
+    # error: 19 [invalid-syntax] "cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)"
     return {n: [x async for x in elements(n)] for n in range(3)}
 ```
 

crates/red_knot_python_semantic/resources/mdtest/snapshots/semantic_syntax_errors.md_-_Semantic_syntax_error_diagnostics_-_`async`_comprehensions_in_synchronous_comprehensions_-_Python_3.10.snap

@@ -16,7 +16,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/diagnostics/semant
  2 |     yield n
  3 | 
  4 | async def f():
- 5 |     # error: 19 [invalid-syntax] "cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)"
+ 5 |     # error: 19 [invalid-syntax] "cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)"
  6 |     return {n: [x async for x in elements(n)] for n in range(3)}
  7 | async def test():
  8 |     return [[x async for x in elements(n)] async for n in range(3)]
@@ -36,9 +36,9 @@ error: invalid-syntax
  --> /src/mdtest_snippet.py:6:19
   |
 4 | async def f():
-5 |     # error: 19 [invalid-syntax] "cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax...
+5 |     # error: 19 [invalid-syntax] "cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (synt...
 6 |     return {n: [x async for x in elements(n)] for n in range(3)}
-  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
 7 | async def test():
 8 |     return [[x async for x in elements(n)] async for n in range(3)]
   |

crates/ruff_linter/src/checkers/ast/mod.rs

@@ -615,7 +615,7 @@ impl SemanticSyntaxContext for Checker<'_> {
             | SemanticSyntaxErrorKind::DuplicateMatchKey(_)
             | SemanticSyntaxErrorKind::DuplicateMatchClassAttribute(_)
             | SemanticSyntaxErrorKind::InvalidStarExpression
-            | SemanticSyntaxErrorKind::AsyncComprehensionOutsideAsyncFunction(_)
+            | SemanticSyntaxErrorKind::AsyncComprehensionInSyncComprehension(_)
             | SemanticSyntaxErrorKind::DuplicateParameter(_) => {
                 if self.settings.preview.is_enabled() {
                     self.semantic_errors.borrow_mut().push(error);

crates/ruff_linter/src/linter.rs

@@ -1022,6 +1022,7 @@ mod tests {
 		",
         PythonVersion::PY310
     )]
+    #[test_case("false_positive", "[x async for x in y]", PythonVersion::PY310)]
     fn test_async_comprehension_in_sync_comprehension(
         name: &str,
         contents: &str,

crates/ruff_linter/src/snapshots/ruff_linter__linter__tests__async_comprehension_in_sync_comprehension_error_on_310_3.10.snap

@@ -1,7 +1,7 @@
 ---
 source: crates/ruff_linter/src/linter.rs
 ---
-<filename>:1:27: SyntaxError: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+<filename>:1:27: SyntaxError: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
   |
 1 | async def f(): return [[x async for x in foo(n)] for n in range(3)]
   |                           ^^^^^^^^^^^^^^^^^^^^^

crates/ruff_linter/src/snapshots/ruff_linter__linter__tests__async_comprehension_in_sync_comprehension_false_positive_3.10.snap

@@ -0,0 +1,3 @@
+---
+source: crates/ruff_linter/src/linter.rs
+---

crates/ruff_linter/src/snapshots/ruff_linter__linter__tests__async_comprehension_in_sync_comprehension_notebook_3.10.snap

@@ -1,7 +1,7 @@
 ---
 source: crates/ruff_linter/src/linter.rs
 ---
-resources/test/fixtures/syntax_errors/async_comprehension.ipynb:3:5: SyntaxError: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+resources/test/fixtures/syntax_errors/async_comprehension.ipynb:3:5: SyntaxError: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
   |
 1 | async def elements(n): yield n
 2 | [x async for x in elements(5)]  # okay, async at top level

crates/ruff_python_parser/src/semantic_errors.rs

@@ -573,7 +573,7 @@ impl SemanticSyntaxChecker {
                 elt, generators, ..
             }) => {
                 Self::check_generator_expr(elt, generators, ctx);
-                Self::async_comprehension_outside_async_function(ctx, generators);
+                Self::async_comprehension_in_sync_comprehension(ctx, generators);
                 for generator in generators.iter().filter(|g| g.is_async) {
                     Self::await_outside_async_function(
                         ctx,
@@ -590,7 +590,7 @@ impl SemanticSyntaxChecker {
             }) => {
                 Self::check_generator_expr(key, generators, ctx);
                 Self::check_generator_expr(value, generators, ctx);
-                Self::async_comprehension_outside_async_function(ctx, generators);
+                Self::async_comprehension_in_sync_comprehension(ctx, generators);
                 for generator in generators.iter().filter(|g| g.is_async) {
                     Self::await_outside_async_function(
                         ctx,
@@ -801,7 +801,7 @@ impl SemanticSyntaxChecker {
         }
     }
 
-    fn async_comprehension_outside_async_function<Ctx: SemanticSyntaxContext>(
+    fn async_comprehension_in_sync_comprehension<Ctx: SemanticSyntaxContext>(
         ctx: &Ctx,
         generators: &[ast::Comprehension],
     ) {
@@ -813,7 +813,7 @@ impl SemanticSyntaxChecker {
         if ctx.in_notebook() && ctx.in_module_scope() {
             return;
         }
-        if ctx.in_async_context() && !ctx.in_sync_comprehension() {
+        if !ctx.in_sync_comprehension() {
             return;
         }
         for generator in generators.iter().filter(|gen| gen.is_async) {
@@ -845,7 +845,7 @@ impl SemanticSyntaxChecker {
             // async def j(): return [([y for y in range(1)], [z async for z in range(2)]) for x in range(5)]
             Self::add_error(
                 ctx,
-                SemanticSyntaxErrorKind::AsyncComprehensionOutsideAsyncFunction(python_version),
+                SemanticSyntaxErrorKind::AsyncComprehensionInSyncComprehension(python_version),
                 generator.range,
             );
         }
@@ -914,11 +914,11 @@ impl Display for SemanticSyntaxError {
             SemanticSyntaxErrorKind::InvalidStarExpression => {
                 f.write_str("can't use starred expression here")
             }
-            SemanticSyntaxErrorKind::AsyncComprehensionOutsideAsyncFunction(python_version) => {
+            SemanticSyntaxErrorKind::AsyncComprehensionInSyncComprehension(python_version) => {
                 write!(
                     f,
-                    "cannot use an asynchronous comprehension outside of an asynchronous \
-                                function on Python {python_version} (syntax was added in 3.11)",
+                    "cannot use an asynchronous comprehension inside of a synchronous comprehension \
+                        on Python {python_version} (syntax was added in 3.11)",
                 )
             }
             SemanticSyntaxErrorKind::YieldOutsideFunction(kind) => {
@@ -1187,7 +1187,7 @@ pub enum SemanticSyntaxErrorKind {
     /// This was discussed in [BPO 33346] and fixed in Python 3.11.
     ///
     /// [BPO 33346]: https://github.com/python/cpython/issues/77527
-    AsyncComprehensionOutsideAsyncFunction(PythonVersion),
+    AsyncComprehensionInSyncComprehension(PythonVersion),
 
     /// Represents the use of `yield`, `yield from`, or `await` outside of a function scope.
     ///

crates/ruff_python_parser/tests/snapshots/invalid_syntax@nested_async_comprehension_py310.py.snap

@@ -780,7 +780,7 @@ Module(
   |
 1 | # parse_options: {"target-version": "3.10"}
 2 | async def f(): return [[x async for x in foo(n)] for n in range(3)]    # list
-  |                           ^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+  |                           ^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
 3 | async def g(): return [{x: 1 async for x in foo(n)} for n in range(3)] # dict
 4 | async def h(): return [{x async for x in foo(n)} for n in range(3)]    # set
   |
@@ -790,7 +790,7 @@ Module(
 1 | # parse_options: {"target-version": "3.10"}
 2 | async def f(): return [[x async for x in foo(n)] for n in range(3)]    # list
 3 | async def g(): return [{x: 1 async for x in foo(n)} for n in range(3)] # dict
-  |                              ^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+  |                              ^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
 4 | async def h(): return [{x async for x in foo(n)} for n in range(3)]    # set
 5 | async def i(): return [([y async for y in range(1)], [z for z in range(2)]) for x in range(5)]
   |
@@ -800,7 +800,7 @@ Module(
 2 | async def f(): return [[x async for x in foo(n)] for n in range(3)]    # list
 3 | async def g(): return [{x: 1 async for x in foo(n)} for n in range(3)] # dict
 4 | async def h(): return [{x async for x in foo(n)} for n in range(3)]    # set
-  |                           ^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+  |                           ^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
 5 | async def i(): return [([y async for y in range(1)], [z for z in range(2)]) for x in range(5)]
 6 | async def j(): return [([y for y in range(1)], [z async for z in range(2)]) for x in range(5)]
   |
@@ -810,7 +810,7 @@ Module(
 3 | async def g(): return [{x: 1 async for x in foo(n)} for n in range(3)] # dict
 4 | async def h(): return [{x async for x in foo(n)} for n in range(3)]    # set
 5 | async def i(): return [([y async for y in range(1)], [z for z in range(2)]) for x in range(5)]
-  |                            ^^^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+  |                            ^^^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
 6 | async def j(): return [([y for y in range(1)], [z async for z in range(2)]) for x in range(5)]
   |
 
@@ -819,5 +819,5 @@ Module(
 4 | async def h(): return [{x async for x in foo(n)} for n in range(3)]    # set
 5 | async def i(): return [([y async for y in range(1)], [z for z in range(2)]) for x in range(5)]
 6 | async def j(): return [([y for y in range(1)], [z async for z in range(2)]) for x in range(5)]
-  |                                                   ^^^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension outside of an asynchronous function on Python 3.10 (syntax was added in 3.11)
+  |                                                   ^^^^^^^^^^^^^^^^^^^^^^^ Syntax Error: cannot use an asynchronous comprehension inside of a synchronous comprehension on Python 3.10 (syntax was added in 3.11)
   |