[ty] Implemented "go to definition" support for import statements (#19428)

This PR extends the "go to declaration" and "go to definition"
functionality to support import statements — both standard imports and
"from" import forms.

---------

Co-authored-by: UnboundVariable <unbound@gmail.com>

crates/ty_python_semantic/src/lib.rs

@@ -17,8 +17,10 @@ pub use program::{
 pub use python_platform::PythonPlatform;
 pub use semantic_model::{Completion, CompletionKind, HasType, NameKind, SemanticModel};
 pub use site_packages::{PythonEnvironment, SitePackagesPaths, SysPrefixPathOrigin};
-pub use types::ide_support::ResolvedDefinition;
-pub use types::{definitions_for_attribute, definitions_for_name};
+pub use types::ide_support::{
+    ResolvedDefinition, definitions_for_attribute, definitions_for_imported_symbol,
+    definitions_for_name,
+};
 pub use util::diagnostics::add_inferred_python_version_hint_to_diagnostic;
 
 pub mod ast_node_ref;

crates/ty_python_semantic/src/types.rs

@@ -49,7 +49,8 @@ use crate::types::generics::{
 };
 pub use crate::types::ide_support::{
     CallSignatureDetails, Member, all_members, call_signature_details, definition_kind_for_name,
-    definitions_for_attribute, definitions_for_keyword_argument, definitions_for_name,
+    definitions_for_attribute, definitions_for_imported_symbol, definitions_for_keyword_argument,
+    definitions_for_name,
 };
 use crate::types::infer::infer_unpack_types;
 use crate::types::mro::{Mro, MroError, MroIterator};

crates/ty_python_semantic/src/types/ide_support.rs

@@ -682,6 +682,25 @@ pub fn definitions_for_keyword_argument<'db>(
     resolved_definitions
 }
 
+/// Find the definitions for a symbol imported via `from x import y as z` statement.
+/// This function handles the case where the cursor is on the original symbol name `y`.
+/// Returns the same definitions as would be found for the alias `z`.
+pub fn definitions_for_imported_symbol<'db>(
+    db: &'db dyn Db,
+    file: File,
+    import_node: &ast::StmtImportFrom,
+    symbol_name: &str,
+) -> Vec<ResolvedDefinition<'db>> {
+    let mut visited = FxHashSet::default();
+    resolve_definition::resolve_from_import_definitions(
+        db,
+        file,
+        import_node,
+        symbol_name,
+        &mut visited,
+    )
+}
+
 /// Details about a callable signature for IDE support.
 #[derive(Debug, Clone)]
 pub struct CallSignatureDetails<'db> {
@@ -888,7 +907,7 @@ mod resolve_definition {
     }
 
     /// Helper function to resolve import definitions for `ImportFrom` and `StarImport` cases.
-    fn resolve_from_import_definitions<'db>(
+    pub(crate) fn resolve_from_import_definitions<'db>(
         db: &'db dyn Db,
         file: File,
         import_node: &ast::StmtImportFrom,