[ty] Offer "Did you mean...?" suggestions for unresolved from imports and unresolved attributes (#18705)

Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>

crates/ty_python_semantic/resources/mdtest/attributes.md

@@ -2167,6 +2167,57 @@ reveal_type(Foo.BAR.value)  # revealed: @Todo(Attribute access on enum classes)
 reveal_type(Foo.__members__)  # revealed: @Todo(Attribute access on enum classes)
 ```
 
+## Suggestions for obvious typos
+
+<!-- snapshot-diagnostics -->
+
+For obvious typos, we add a "Did you mean...?" suggestion to the diagnostic.
+
+```py
+import collections
+
+print(collections.dequee)  # error: [unresolved-attribute]
+```
+
+But the suggestion is suppressed if the only close matches start with a leading underscore:
+
+```py
+class Foo:
+    _bar = 42
+
+print(Foo.bar)  # error: [unresolved-attribute]
+```
+
+The suggestion is not suppressed if the typo itself starts with a leading underscore, however:
+
+```py
+print(Foo._barr)  # error: [unresolved-attribute]
+```
+
+And in method contexts, the suggestion is never suppressed if accessing an attribute on an instance
+of the method's enclosing class:
+
+```py
+class Bar:
+    _attribute = 42
+
+    def f(self, x: "Bar"):
+        # TODO: we should emit `[unresolved-attribute]` here, should have the same behaviour as `x.attribute` below
+        print(self.attribute)
+
+        # We give a suggestion here, even though the only good candidates start with underscores and the typo does not,
+        # because we're in a method context and `x` is an instance of the enclosing class.
+        print(x.attribute)  # error: [unresolved-attribute]
+
+class Baz:
+    def f(self, x: Bar):
+        # No suggestion is given here, because:
+        # - the good suggestions all start with underscores
+        # - the typo does not start with an underscore
+        # - We *are* in a method context, but `x` is not an instance of the enclosing class
+        print(x.attribute)  # error: [unresolved-attribute]
+```
+
 ## References
 
 Some of the tests in the *Class and instance variables* section draw inspiration from

crates/ty_python_semantic/resources/mdtest/import/basic.md

@@ -205,3 +205,39 @@ python-version = "3.13"
 import aifc  # error: [unresolved-import]
 from distutils import sysconfig  # error: [unresolved-import]
 ```
+
+## `from` import that has a typo
+
+We offer a "Did you mean?" subdiagnostic suggestion if there's a name in the module that's
+reasonably similar to the unresolved member.
+
+<!-- snapshot-diagnostics -->
+
+`foo.py`:
+
+```py
+from collections import dequee  # error: [unresolved-import]
+```
+
+However, we suppress the suggestion if the only close matches in the module start with a leading
+underscore:
+
+`bar.py`:
+
+```py
+from baz import foo  # error: [unresolved-import]
+```
+
+`baz.py`:
+
+```py
+_foo = 42
+```
+
+The suggestion is never suppressed if the typo itself starts with a leading underscore, however:
+
+`eggs.py`:
+
+```py
+from baz import _fooo  # error: [unresolved-import]
+```

crates/ty_python_semantic/resources/mdtest/snapshots/attributes.md_-_Attributes_-_Suggestions_for_obvi…_(bf7b28ef99f0ec16).snap

@@ -0,0 +1,115 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: attributes.md - Attributes - Suggestions for obvious typos
+mdtest path: crates/ty_python_semantic/resources/mdtest/attributes.md
+---
+
+# Python source files
+
+## mdtest_snippet.py
+
+```
+ 1 | import collections
+ 2 | 
+ 3 | print(collections.dequee)  # error: [unresolved-attribute]
+ 4 | class Foo:
+ 5 |     _bar = 42
+ 6 | 
+ 7 | print(Foo.bar)  # error: [unresolved-attribute]
+ 8 | print(Foo._barr)  # error: [unresolved-attribute]
+ 9 | class Bar:
+10 |     _attribute = 42
+11 | 
+12 |     def f(self, x: "Bar"):
+13 |         # TODO: we should emit `[unresolved-attribute]` here, should have the same behaviour as `x.attribute` below
+14 |         print(self.attribute)
+15 | 
+16 |         # We give a suggestion here, even though the only good candidates start with underscores and the typo does not,
+17 |         # because we're in a method context and `x` is an instance of the enclosing class.
+18 |         print(x.attribute)  # error: [unresolved-attribute]
+19 | 
+20 | class Baz:
+21 |     def f(self, x: Bar):
+22 |         # No suggestion is given here, because:
+23 |         # - the good suggestions all start with underscores
+24 |         # - the typo does not start with an underscore
+25 |         # - We *are* in a method context, but `x` is not an instance of the enclosing class
+26 |         print(x.attribute)  # error: [unresolved-attribute]
+```
+
+# Diagnostics
+
+```
+error[unresolved-attribute]: Type `<module 'collections'>` has no attribute `dequee`
+ --> src/mdtest_snippet.py:3:7
+  |
+1 | import collections
+2 |
+3 | print(collections.dequee)  # error: [unresolved-attribute]
+  |       ^^^^^^^^^^^^^^^^^^ Did you mean `deque`?
+4 | class Foo:
+5 |     _bar = 42
+  |
+info: rule `unresolved-attribute` is enabled by default
+
+```
+
+```
+error[unresolved-attribute]: Type `<class 'Foo'>` has no attribute `bar`
+ --> src/mdtest_snippet.py:7:7
+  |
+5 |     _bar = 42
+6 |
+7 | print(Foo.bar)  # error: [unresolved-attribute]
+  |       ^^^^^^^
+8 | print(Foo._barr)  # error: [unresolved-attribute]
+9 | class Bar:
+  |
+info: rule `unresolved-attribute` is enabled by default
+
+```
+
+```
+error[unresolved-attribute]: Type `<class 'Foo'>` has no attribute `_barr`
+  --> src/mdtest_snippet.py:8:7
+   |
+ 7 | print(Foo.bar)  # error: [unresolved-attribute]
+ 8 | print(Foo._barr)  # error: [unresolved-attribute]
+   |       ^^^^^^^^^ Did you mean `_bar`?
+ 9 | class Bar:
+10 |     _attribute = 42
+   |
+info: rule `unresolved-attribute` is enabled by default
+
+```
+
+```
+error[unresolved-attribute]: Type `Bar` has no attribute `attribute`
+  --> src/mdtest_snippet.py:18:15
+   |
+16 |         # We give a suggestion here, even though the only good candidates start with underscores and the typo does not,
+17 |         # because we're in a method context and `x` is an instance of the enclosing class.
+18 |         print(x.attribute)  # error: [unresolved-attribute]
+   |               ^^^^^^^^^^^ Did you mean `_attribute`?
+19 |
+20 | class Baz:
+   |
+info: rule `unresolved-attribute` is enabled by default
+
+```
+
+```
+error[unresolved-attribute]: Type `Bar` has no attribute `attribute`
+  --> src/mdtest_snippet.py:26:15
+   |
+24 |         # - the typo does not start with an underscore
+25 |         # - We *are* in a method context, but `x` is not an instance of the enclosing class
+26 |         print(x.attribute)  # error: [unresolved-attribute]
+   |               ^^^^^^^^^^^
+   |
+info: rule `unresolved-attribute` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/snapshots/basic.md_-_Structures_-_`from`_import_that_h…_(3caffc60d8390adf).snap

@@ -0,0 +1,69 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: basic.md - Structures - `from` import that has a typo
+mdtest path: crates/ty_python_semantic/resources/mdtest/import/basic.md
+---
+
+# Python source files
+
+## foo.py
+
+```
+1 | from collections import dequee  # error: [unresolved-import]
+```
+
+## bar.py
+
+```
+1 | from baz import foo  # error: [unresolved-import]
+```
+
+## baz.py
+
+```
+1 | _foo = 42
+```
+
+## eggs.py
+
+```
+1 | from baz import _fooo  # error: [unresolved-import]
+```
+
+# Diagnostics
+
+```
+error[unresolved-import]: Module `collections` has no member `dequee`
+ --> src/foo.py:1:25
+  |
+1 | from collections import dequee  # error: [unresolved-import]
+  |                         ^^^^^^ Did you mean `deque`?
+  |
+info: rule `unresolved-import` is enabled by default
+
+```
+
+```
+error[unresolved-import]: Module `baz` has no member `foo`
+ --> src/bar.py:1:17
+  |
+1 | from baz import foo  # error: [unresolved-import]
+  |                 ^^^
+  |
+info: rule `unresolved-import` is enabled by default
+
+```
+
+```
+error[unresolved-import]: Module `baz` has no member `_fooo`
+ --> src/eggs.py:1:17
+  |
+1 | from baz import _fooo  # error: [unresolved-import]
+  |                 ^^^^^ Did you mean `_foo`?
+  |
+info: rule `unresolved-import` is enabled by default
+
+```