[ty] Emit error for invalid binary operations in type expressions (#18991)

## Summary

This PR adds diagnostic for invalid binary operators in type
expressions. It should close https://github.com/astral-sh/ty/issues/706
if merged.

Please feel free to suggest better wordings for the diagnostic message.

## Test Plan

I modified `mdtest/annotations/invalid.md` and added a test for each
binary operator, and fixed tests that was broken by the new diagnostic.

crates/ty_python_semantic/resources/mdtest/annotations/invalid.md

@@ -91,6 +91,40 @@ async def outer():  # avoid unrelated syntax errors on yield, yield from, and aw
         reveal_type(p)  # revealed: Unknown
         reveal_type(q)  # revealed: int | Unknown
         reveal_type(r)  # revealed: @Todo(unknown type subscript)
+
+class Mat:
+    def __init__(self, value: int):
+        self.value = value
+
+    def __matmul__(self, other) -> int:
+        return 42
+
+def invalid_binary_operators(
+    a: "1" + "2",  # error: [invalid-type-form] "Invalid binary operator `+` in type annotation"
+    b: 3 - 5.0,  # error: [invalid-type-form] "Invalid binary operator `-` in type annotation"
+    c: 4 * -2,  # error: [invalid-type-form] "Invalid binary operator `*` in type annotation"
+    d: Mat(4) @ Mat(2),  # error: [invalid-type-form] "Invalid binary operator `@` in type annotation"
+    e: 10 / 2,  # error: [invalid-type-form] "Invalid binary operator `/` in type annotation"
+    f: 10 % 3,  # error: [invalid-type-form] "Invalid binary operator `%` in type annotation"
+    g: 2**-0.5,  # error: [invalid-type-form] "Invalid binary operator `**` in type annotation"
+    h: 10 // 3,  # error: [invalid-type-form] "Invalid binary operator `//` in type annotation"
+    i: 1 << 2,  # error: [invalid-type-form] "Invalid binary operator `<<` in type annotation"
+    j: 4 >> 42,  # error: [invalid-type-form] "Invalid binary operator `>>` in type annotation"
+    k: 5 ^ 3,  # error: [invalid-type-form] "Invalid binary operator `^` in type annotation"
+    l: 5 & 3,  # error: [invalid-type-form] "Invalid binary operator `&` in type annotation"
+):
+    reveal_type(a)  # revealed: Unknown
+    reveal_type(b)  # revealed: Unknown
+    reveal_type(c)  # revealed: Unknown
+    reveal_type(d)  # revealed: Unknown
+    reveal_type(e)  # revealed: Unknown
+    reveal_type(f)  # revealed: Unknown
+    reveal_type(g)  # revealed: Unknown
+    reveal_type(h)  # revealed: Unknown
+    reveal_type(i)  # revealed: Unknown
+    reveal_type(j)  # revealed: Unknown
+    reveal_type(k)  # revealed: Unknown
+    reveal_type(l)  # revealed: Unknown
 ```
 
 ## Invalid Collection based AST nodes

crates/ty_python_semantic/resources/mdtest/annotations/string.md

@@ -154,6 +154,7 @@ shouldn't panic.
 ```py
 a: "1 or 2"
 b: "(x := 1)"
+# error: [invalid-type-form]
 c: "1 + 2"
 d: "lambda x: x"
 e: "x if True else y"

crates/ty_python_semantic/resources/mdtest/type_properties/is_disjoint_from.md

@@ -251,7 +251,7 @@ static_assert(is_disjoint_from(Intersection[int, Any], Not[int]))
 static_assert(is_disjoint_from(Not[int], Intersection[int, Any]))
 
 # TODO https://github.com/astral-sh/ty/issues/216
-static_assert(is_disjoint_from(AlwaysFalsy, LiteralString & ~Literal[""]))  # error: [static-assert-error]
+static_assert(is_disjoint_from(AlwaysFalsy, Intersection[LiteralString, Not[Literal[""]]]))  # error: [static-assert-error]
 ```
 
 ## Special types

crates/ty_python_semantic/src/types/infer.rs

@@ -8416,8 +8416,17 @@ impl<'db> TypeInferenceBuilder<'db, '_> {
                         UnionType::from_elements(self.db(), [left_ty, right_ty])
                     }
                     // anything else is an invalid annotation:
-                    _ => {
+                    op => {
                         self.infer_binary_expression(binary);
+                        if let Some(mut diag) = self.report_invalid_type_expression(
+                            expression,
+                            format_args!(
+                                "Invalid binary operator `{}` in type annotation",
+                                op.as_str()
+                            ),
+                        ) {
+                            diag.info("Did you mean to use `|`?");
+                        }
                         Type::unknown()
                     }
                 }