[ty] Improved diagnostic for reassignments of Final symbols (#19214)

## Summary

Implement [this
suggestion](https://github.com/astral-sh/ruff/pull/19178#discussion_r2192658146)
by @AlexWaygood.


![image](https://github.com/user-attachments/assets/f183d691-ef6e-43a2-b005-3a32205bc408)

crates/ty_python_semantic/resources/mdtest/snapshots/final.md_-_`typing.Final`_-_Full_diagnostics_(174fdd8134fb325b).snap

@@ -12,30 +12,47 @@ mdtest path: crates/ty_python_semantic/resources/mdtest/type_qualifiers/final.md
 ## mdtest_snippet.py
 
 ```
-1 | from typing import Final
+ 1 | from typing import Final
-2 | 
+ 2 | 
-3 | MY_CONSTANT: Final[int] = 1
+ 3 | MY_CONSTANT: Final[int] = 1
-4 | 
+ 4 | 
-5 | # more code
+ 5 | # more code
-6 | 
+ 6 | 
-7 | MY_CONSTANT = 2  # error: [invalid-assignment]
+ 7 | MY_CONSTANT = 2  # error: [invalid-assignment]
+ 8 | from _stat import ST_INO
+ 9 | 
+10 | ST_INO = 1  # error: [invalid-assignment]
 ```
 
 # Diagnostics
 
 ```
 error[invalid-assignment]: Reassignment of `Final` symbol `MY_CONSTANT` is not allowed
- --> src/mdtest_snippet.py:3:1
+ --> src/mdtest_snippet.py:3:14
   |
 1 | from typing import Final
 2 |
 3 | MY_CONSTANT: Final[int] = 1
-  | --------------------------- Original definition
+  |              ---------- Symbol declared as `Final` here
 4 |
 5 | # more code
 6 |
 7 | MY_CONSTANT = 2  # error: [invalid-assignment]
-  | ^^^^^^^^^^^ Reassignment of `Final` symbol
+  | ^^^^^^^^^^^^^^^ Symbol later reassigned here
+8 | from _stat import ST_INO
+  |
+info: rule `invalid-assignment` is enabled by default
+
+```
+
+```
+error[invalid-assignment]: Reassignment of `Final` symbol `ST_INO` is not allowed
+  --> src/mdtest_snippet.py:10:1
+   |
+ 8 | from _stat import ST_INO
+ 9 |
+10 | ST_INO = 1  # error: [invalid-assignment]
+   | ^^^^^^^^^^ Reassignment of `Final` symbol
    |
 info: rule `invalid-assignment` is enabled by default
 

crates/ty_python_semantic/resources/mdtest/type_qualifiers/final.md

@@ -260,6 +260,8 @@ class C:
 
 <!-- snapshot-diagnostics -->
 
+Annotated assignment:
+
 ```py
 from typing import Final
 
@@ -270,4 +272,12 @@ MY_CONSTANT: Final[int] = 1
 MY_CONSTANT = 2  # error: [invalid-assignment]
 ```
 
+Imported `Final` symbol:
+
+```py
+from _stat import ST_INO
+
+ST_INO = 1  # error: [invalid-assignment]
+```
+
 [`typing.final`]: https://docs.python.org/3/library/typing.html#typing.Final

crates/ty_python_semantic/src/types/infer.rs

@@ -1663,7 +1663,10 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
 
             if !is_local || previous_definition.is_some() {
                 let place = place_table.place_expr(binding.place(db));
-                if let Some(builder) = self.context.report_lint(&INVALID_ASSIGNMENT, node) {
+                if let Some(builder) = self.context.report_lint(
+                    &INVALID_ASSIGNMENT,
+                    binding.full_range(self.db(), self.module()),
+                ) {
                     let mut diagnostic = builder.into_diagnostic(format_args!(
                         "Reassignment of `Final` symbol `{place}` is not allowed"
                     ));
@@ -1676,10 +1679,25 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                         // module, but that information is currently not threaded through attribute
                         // lookup.
                         if !previous_definition.kind(db).is_import() {
-                            let range = previous_definition.full_range(self.db(), self.module());
+                            if let DefinitionKind::AnnotatedAssignment(assignment) =
+                                previous_definition.kind(db)
+                            {
+                                let range = assignment.annotation(self.module()).range();
                                 diagnostic.annotate(
-                                self.context.secondary(range).message("Original definition"),
+                                    self.context
+                                        .secondary(range)
+                                        .message("Symbol declared as `Final` here"),
                                 );
+                            } else {
+                                let range =
+                                    previous_definition.full_range(self.db(), self.module());
+                                diagnostic.annotate(
+                                    self.context
+                                        .secondary(range)
+                                        .message("Symbol declared as `Final` here"),
+                                );
+                            }
+                            diagnostic.set_primary_message("Symbol later reassigned here");
                         }
                     }
                 }