[ty] Make initializer calls GotoTargets (#20014)

This introduces `GotoTarget::Call` that represents the kind of
ambiguous/overloaded click of a callable-being-called:

```py
x = mymodule.MyClass(1, 2)
             ^^^^^^^
```

This is equivalent to `GotoTarget::Expression` for the same span but
enriched
with information about the actual callable implementation.

That is, if you click on `MyClass` in `MyClass()` it is *both* a
reference to the class and to the initializer of the class. Therefore
it would be ideal for goto-* and docstrings to be some intelligent
merging of both the class and the initializer.

In particular the callable-implementation (initializer) is prioritized
over the callable-itself (class) so when showing docstrings we will
preferentially show the docs of the initializer if it exists, and then
fallback to the docs of the class.

For goto-definition/goto-declaration we will yield both the class and
the initializer, requiring you to pick which you want (this is perhaps
needlessly pedantic but...).

Fixes https://github.com/astral-sh/ty/issues/898
Fixes https://github.com/astral-sh/ty/issues/1010

crates/ty_ide/src/goto.rs

@@ -8,14 +8,15 @@ use std::borrow::Cow;
 use crate::find_node::covering_node;
 use crate::stub_mapping::StubMapper;
 use ruff_db::parsed::ParsedModuleRef;
+use ruff_python_ast::ExprCall;
 use ruff_python_ast::{self as ast, AnyNodeRef};
 use ruff_python_parser::TokenKind;
 use ruff_text_size::{Ranged, TextRange, TextSize};
 use ty_python_semantic::HasDefinition;
 use ty_python_semantic::ImportAliasResolution;
 use ty_python_semantic::ResolvedDefinition;
-use ty_python_semantic::types::Type;
 use ty_python_semantic::types::definitions_for_keyword_argument;
+use ty_python_semantic::types::{Type, call_signature_details};
 use ty_python_semantic::{
     HasType, SemanticModel, definitions_for_imported_symbol, definitions_for_name,
 };
@@ -145,6 +146,26 @@ pub(crate) enum GotoTarget<'a> {
     Globals {
         identifier: &'a ast::Identifier,
     },
+    /// Go to on the invocation of a callable
+    ///
+    /// ```py
+    /// x = mymodule.MyClass(1, 2)
+    ///              ^^^^^^^
+    /// ```
+    ///
+    /// This is equivalent to `GotoTarget::Expression(callable)` but enriched
+    /// with information about the actual callable implementation.
+    ///
+    /// That is, if you click on `MyClass` in `MyClass()` it is *both* a
+    /// reference to the class and to the initializer of the class. Therefore
+    /// it would be ideal for goto-* and docstrings to be some intelligent
+    /// merging of both the class and the initializer.
+    Call {
+        /// The callable that can actually be selected by a cursor
+        callable: ast::ExprRef<'a>,
+        /// The call of the callable
+        call: &'a ExprCall,
+    },
 }
 
 /// The resolved definitions for a `GotoTarget`
@@ -258,6 +279,9 @@ impl GotoTarget<'_> {
             GotoTarget::ImportModuleAlias { alias } => alias.inferred_type(model),
             GotoTarget::ExceptVariable(except) => except.inferred_type(model),
             GotoTarget::KeywordArgument { keyword, .. } => keyword.value.inferred_type(model),
+            // When asking the type of a callable, usually you want the callable itself?
+            // (i.e. the type of `MyClass` in `MyClass()` is `<class MyClass>` and not `() -> MyClass`)
+            GotoTarget::Call { callable, .. } => callable.inferred_type(model),
             // TODO: Support identifier targets
             GotoTarget::PatternMatchRest(_)
             | GotoTarget::PatternKeywordArgument(_)
@@ -293,18 +317,10 @@ impl GotoTarget<'_> {
         alias_resolution: ImportAliasResolution,
     ) -> Option<DefinitionsOrTargets<'db>> {
         use crate::NavigationTarget;
-        use ruff_python_ast as ast;
 
         match self {
-            GotoTarget::Expression(expression) => match expression {
-                ast::ExprRef::Name(name) => Some(DefinitionsOrTargets::Definitions(
-                    definitions_for_name(db, file, name),
-                )),
-                ast::ExprRef::Attribute(attribute) => Some(DefinitionsOrTargets::Definitions(
-                    ty_python_semantic::definitions_for_attribute(db, file, attribute),
-                )),
-                _ => None,
-            },
+            GotoTarget::Expression(expression) => definitions_for_expression(db, file, expression)
+                .map(DefinitionsOrTargets::Definitions),
 
             // For already-defined symbols, they are their own definitions
             GotoTarget::FunctionDef(function) => {
@@ -417,6 +433,22 @@ impl GotoTarget<'_> {
                 }
             }
 
+            // For callables, both the definition of the callable and the actual function impl are relevant.
+            //
+            // Prefer the function impl over the callable so that its docstrings win if defined.
+            GotoTarget::Call { callable, call } => {
+                let mut definitions = definitions_for_callable(db, file, call);
+                let expr_definitions =
+                    definitions_for_expression(db, file, callable).unwrap_or_default();
+                definitions.extend(expr_definitions);
+
+                if definitions.is_empty() {
+                    None
+                } else {
+                    Some(DefinitionsOrTargets::Definitions(definitions))
+                }
+            }
+
             _ => None,
         }
     }
@@ -427,7 +459,11 @@ impl GotoTarget<'_> {
     /// to this goto target.
     pub(crate) fn to_string(&self) -> Option<Cow<'_, str>> {
         match self {
-            GotoTarget::Expression(expression) => match expression {
+            GotoTarget::Call {
+                callable: expression,
+                ..
+            }
+            | GotoTarget::Expression(expression) => match expression {
                 ast::ExprRef::Name(name) => Some(Cow::Borrowed(name.id.as_str())),
                 ast::ExprRef::Attribute(attr) => Some(Cow::Borrowed(attr.attr.as_str())),
                 _ => None,
@@ -627,7 +663,18 @@ impl GotoTarget<'_> {
                     Some(GotoTarget::TypeParamTypeVarTupleName(var_tuple))
                 }
                 Some(AnyNodeRef::ExprAttribute(attribute)) => {
-                    Some(GotoTarget::Expression(attribute.into()))
+                    // Check if this is seemingly a callable being invoked (the `y` in `x.y(...)`)
+                    let grandparent_expr = covering_node.ancestors().nth(2);
+                    let attribute_expr = attribute.into();
+                    if let Some(AnyNodeRef::ExprCall(call)) = grandparent_expr {
+                        if ruff_python_ast::ExprRef::from(&call.func) == attribute_expr {
+                            return Some(GotoTarget::Call {
+                                call,
+                                callable: attribute_expr,
+                            });
+                        }
+                    }
+                    Some(GotoTarget::Expression(attribute_expr))
                 }
                 Some(AnyNodeRef::StmtNonlocal(_)) => Some(GotoTarget::NonLocal { identifier }),
                 Some(AnyNodeRef::StmtGlobal(_)) => Some(GotoTarget::Globals { identifier }),
@@ -641,7 +688,19 @@ impl GotoTarget<'_> {
                 }
             },
 
-            node => node.as_expr_ref().map(GotoTarget::Expression),
+            node => {
+                // Check if this is seemingly a callable being invoked (the `x` in `x(...)`)
+                let parent = covering_node.parent();
+                if let (Some(AnyNodeRef::ExprCall(call)), AnyNodeRef::ExprName(name)) =
+                    (parent, node)
+                {
+                    return Some(GotoTarget::Call {
+                        call,
+                        callable: name.into(),
+                    });
+                }
+                node.as_expr_ref().map(GotoTarget::Expression)
+            }
         }
     }
 }
@@ -649,7 +708,11 @@ impl GotoTarget<'_> {
 impl Ranged for GotoTarget<'_> {
     fn range(&self) -> TextRange {
         match self {
-            GotoTarget::Expression(expression) => match expression {
+            GotoTarget::Call {
+                callable: expression,
+                ..
+            }
+            | GotoTarget::Expression(expression) => match expression {
                 ast::ExprRef::Attribute(attribute) => attribute.attr.range,
                 _ => expression.range(),
             },
@@ -711,6 +774,35 @@ fn convert_resolved_definitions_to_targets(
         .collect()
 }
 
+/// Shared helper to get definitions for an expr (that is presumably a name/attr)
+fn definitions_for_expression<'db>(
+    db: &'db dyn crate::Db,
+    file: ruff_db::files::File,
+    expression: &ruff_python_ast::ExprRef<'_>,
+) -> Option<Vec<ResolvedDefinition<'db>>> {
+    match expression {
+        ast::ExprRef::Name(name) => Some(definitions_for_name(db, file, name)),
+        ast::ExprRef::Attribute(attribute) => Some(ty_python_semantic::definitions_for_attribute(
+            db, file, attribute,
+        )),
+        _ => None,
+    }
+}
+
+fn definitions_for_callable<'db>(
+    db: &'db dyn crate::Db,
+    file: ruff_db::files::File,
+    call: &ExprCall,
+) -> Vec<ResolvedDefinition<'db>> {
+    let model = SemanticModel::new(db, file);
+    // Attempt to refine to a specific call
+    let signature_info = call_signature_details(db, &model, call);
+    signature_info
+        .into_iter()
+        .filter_map(|signature| signature.definition.map(ResolvedDefinition::Definition))
+        .collect()
+}
+
 /// Shared helper to map and convert resolved definitions into navigation targets.
 fn definitions_to_navigation_targets<'db>(
     db: &dyn crate::Db,

crates/ty_ide/src/goto_declaration.rs

@@ -123,6 +123,23 @@ mod tests {
           |
         4 |         pass
         5 |
+        6 | instance = MyClass()
+          |            ^^^^^^^
+          |
+
+        info[goto-declaration]: Declaration
+         --> main.py:3:9
+          |
+        2 | class MyClass:
+        3 |     def __init__(self):
+          |         ^^^^^^^^
+        4 |         pass
+          |
+        info: Source
+         --> main.py:6:12
+          |
+        4 |         pass
+        5 |
         6 | instance = MyClass()
           |            ^^^^^^^
           |

crates/ty_ide/src/goto_definition.rs

@@ -466,6 +466,22 @@ class MyOtherClass:
          --> main.py:3:5
           |
         2 | from mymodule import MyClass
+        3 | x = MyClass(0)
+          |     ^^^^^^^
+          |
+
+        info[goto-definition]: Definition
+         --> mymodule.py:3:9
+          |
+        2 | class MyClass:
+        3 |     def __init__(self, val):
+          |         ^^^^^^^^
+        4 |         self.val = val
+          |
+        info: Source
+         --> main.py:3:5
+          |
+        2 | from mymodule import MyClass
         3 | x = MyClass(0)
           |     ^^^^^^^
           |

crates/ty_ide/src/hover.rs

@@ -465,6 +465,123 @@ mod tests {
         "#,
         );
 
+        assert_snapshot!(test.hover(), @r"
+        <class 'MyClass'>
+        ---------------------------------------------
+        initializes MyClass (perfectly)
+
+        ---------------------------------------------
+        ```python
+        <class 'MyClass'>
+        ```
+        ---
+        ```text
+        initializes MyClass (perfectly)
+
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+          --> main.py:24:5
+           |
+        22 |         return 0
+        23 |
+        24 | x = MyClass(0)
+           |     ^^^^^-^
+           |     |    |
+           |     |    Cursor offset
+           |     source
+           |
+        ");
+    }
+
+    #[test]
+    fn hover_class_init_attr() {
+        let test = CursorTest::builder()
+            .source(
+                "mymod.py",
+                r#"
+        class MyClass:
+            '''
+                This is such a great class!!
+
+                    Don't you know?
+                
+                Everyone loves my class!!
+
+            '''
+            def __init__(self, val):
+                """initializes MyClass (perfectly)"""
+                self.val = val
+        "#,
+            )
+            .source(
+                "main.py",
+                r#"
+        import mymod
+
+        x = mymod.MyCla<CURSOR>ss(0)
+        "#,
+            )
+            .build();
+
+        assert_snapshot!(test.hover(), @r"
+        <class 'MyClass'>
+        ---------------------------------------------
+        initializes MyClass (perfectly)
+
+        ---------------------------------------------
+        ```python
+        <class 'MyClass'>
+        ```
+        ---
+        ```text
+        initializes MyClass (perfectly)
+
+        ```
+        ---------------------------------------------
+        info[hover]: Hovered content is
+         --> main.py:4:11
+          |
+        2 | import mymod
+        3 |
+        4 | x = mymod.MyClass(0)
+          |           ^^^^^-^
+          |           |    |
+          |           |    Cursor offset
+          |           source
+          |
+        ");
+    }
+
+    #[test]
+    fn hover_class_init_no_init_docs() {
+        let test = cursor_test(
+            r#"
+        class MyClass:
+            '''
+                This is such a great class!!
+
+                    Don't you know?
+                
+                Everyone loves my class!!
+
+            '''
+            def __init__(self, val):
+                self.val = val
+            
+            def my_method(self, a, b):
+                '''This is such a great func!!
+
+                Args:
+                    a: first for a reason
+                    b: coming for `a`'s title
+                '''
+                return 0
+
+        x = MyCla<CURSOR>ss(0)
+        "#,
+        );
+
         assert_snapshot!(test.hover(), @r"
         <class 'MyClass'>
         ---------------------------------------------
@@ -489,11 +606,11 @@ mod tests {
         ```
         ---------------------------------------------
         info[hover]: Hovered content is
-          --> main.py:24:5
+          --> main.py:23:5
            |
-        22 |         return 0
-        23 |
-        24 | x = MyClass(0)
+        21 |         return 0
+        22 |
+        23 | x = MyClass(0)
            |     ^^^^^-^
            |     |    |
            |     |    Cursor offset