[red-knot] Do not show types for literal expressions on hover (#17290)

## Summary

Resolves #17289.

After this change, Red Knot will no longer show types on hover for
`None`, `...`, `True`, `False`, numbers, strings (but not f-strings),
and bytes literals.

## Test Plan

Unit tests.

crates/red_knot_ide/src/hover.rs

@@ -1,4 +1,4 @@
-use crate::goto::find_goto_target;
+use crate::goto::{find_goto_target, GotoTarget};
 use crate::{Db, MarkupKind, RangedValue};
 use red_knot_python_semantic::types::Type;
 use red_knot_python_semantic::SemanticModel;
@@ -12,6 +12,12 @@ pub fn hover(db: &dyn Db, file: File, offset: TextSize) -> Option<RangedValue<Ho
     let parsed = parsed_module(db.upcast(), file);
     let goto_target = find_goto_target(parsed, offset)?;
 
+    if let GotoTarget::Expression(expr) = goto_target {
+        if expr.is_literal_expr() {
+            return None;
+        }
+    }
+
     let model = SemanticModel::new(db.upcast(), file);
     let ty = goto_target.inferred_type(&model)?;
 
@@ -496,6 +502,57 @@ mod tests {
         ");
     }
 
+    #[test]
+    fn hover_whitespace() {
+        let test = cursor_test(
+            r#"
+        class C:
+            <CURSOR>
+            foo: str = 'bar'
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @"Hover provided no content");
+    }
+
+    #[test]
+    fn hover_literal_int() {
+        let test = cursor_test(
+            r#"
+        print(
+            0 + 1<CURSOR>
+        )
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @"Hover provided no content");
+    }
+
+    #[test]
+    fn hover_literal_ellipsis() {
+        let test = cursor_test(
+            r#"
+        print(
+            .<CURSOR>..
+        )
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @"Hover provided no content");
+    }
+
+    #[test]
+    fn hover_docstring() {
+        let test = cursor_test(
+            r#"
+        def f():
+            """Lorem ipsum dolor sit amet.<CURSOR>"""
+        "#,
+        );
+
+        assert_snapshot!(test.hover(), @"Hover provided no content");
+    }
+
     impl CursorTest {
         fn hover(&self) -> String {
             use std::fmt::Write;

crates/ruff_python_ast/src/nodes.rs

@@ -102,6 +102,19 @@ impl Expr {
 }
 
 impl ExprRef<'_> {
+    /// See [`Expr::is_literal_expr`].
+    pub fn is_literal_expr(&self) -> bool {
+        matches!(
+            self,
+            ExprRef::StringLiteral(_)
+                | ExprRef::BytesLiteral(_)
+                | ExprRef::NumberLiteral(_)
+                | ExprRef::BooleanLiteral(_)
+                | ExprRef::NoneLiteral(_)
+                | ExprRef::EllipsisLiteral(_)
+        )
+    }
+
     pub fn precedence(&self) -> OperatorPrecedence {
         OperatorPrecedence::from(self)
     }