move call-info to a separate file

1 files changed, 119 insertions, 0 deletions

diff --git a/crates/ra_analysis/src/call_info.rs b/crates/ra_analysis/src/call_info.rs
new file mode 100644
index 000000000..a31a54ef6
--- /dev/null
+++ b/crates/ra_analysis/src/call_info.rs
@@ -0,0 +1,119 @@
+use ra_db::{SyntaxDatabase, Cancelable};
+use ra_syntax::{
+    AstNode, SyntaxNode, TextUnit, TextRange,
+    SyntaxKind::FN_DEF,
+    ast::{self, ArgListOwner},
+};
+use ra_editor::find_node_at_offset;
+use hir::FnSignatureInfo;
+
+use crate::{FilePosition, db::RootDatabase};
+
+/// Computes parameter information for the given call expression.
+pub(crate) fn call_info(
+    db: &RootDatabase,
+    position: FilePosition,
+) -> Cancelable<Option<(FnSignatureInfo, Option<usize>)>> {
+    let file = db.source_file(position.file_id);
+    let syntax = file.syntax();
+
+    // Find the calling expression and it's NameRef
+    let calling_node = ctry!(FnCallNode::with_node(syntax, position.offset));
+    let name_ref = ctry!(calling_node.name_ref());
+
+    // Resolve the function's NameRef (NOTE: this isn't entirely accurate).
+    let file_symbols = db.index_resolve(name_ref)?;
+    for symbol in file_symbols {
+        if symbol.ptr.kind() == FN_DEF {
+            let fn_file = db.source_file(symbol.file_id);
+            let fn_def = symbol.ptr.resolve(&fn_file);
+            let fn_def = ast::FnDef::cast(&fn_def).unwrap();
+            let descr = ctry!(hir::source_binder::function_from_source(
+                db,
+                symbol.file_id,
+                fn_def
+            )?);
+            if let Some(descriptor) = descr.signature_info(db) {
+                // If we have a calling expression let's find which argument we are on
+                let mut current_parameter = None;
+
+                let num_params = descriptor.params.len();
+                let has_self = fn_def.param_list().and_then(|l| l.self_param()).is_some();
+
+                if num_params == 1 {
+                    if !has_self {
+                        current_parameter = Some(0);
+                    }
+                } else if num_params > 1 {
+                    // Count how many parameters into the call we are.
+                    // TODO: This is best effort for now and should be fixed at some point.
+                    // It may be better to see where we are in the arg_list and then check
+                    // where offset is in that list (or beyond).
+                    // Revisit this after we get documentation comments in.
+                    if let Some(ref arg_list) = calling_node.arg_list() {
+                        let start = arg_list.syntax().range().start();
+
+                        let range_search = TextRange::from_to(start, position.offset);
+                        let mut commas: usize = arg_list
+                            .syntax()
+                            .text()
+                            .slice(range_search)
+                            .to_string()
+                            .matches(',')
+                            .count();
+
+                        // If we have a method call eat the first param since it's just self.
+                        if has_self {
+                            commas += 1;
+                        }
+
+                        current_parameter = Some(commas);
+                    }
+                }
+
+                return Ok(Some((descriptor, current_parameter)));
+            }
+        }
+    }
+
+    Ok(None)
+}
+
+enum FnCallNode<'a> {
+    CallExpr(&'a ast::CallExpr),
+    MethodCallExpr(&'a ast::MethodCallExpr),
+}
+
+impl<'a> FnCallNode<'a> {
+    pub fn with_node(syntax: &'a SyntaxNode, offset: TextUnit) -> Option<FnCallNode<'a>> {
+        if let Some(expr) = find_node_at_offset::<ast::CallExpr>(syntax, offset) {
+            return Some(FnCallNode::CallExpr(expr));
+        }
+        if let Some(expr) = find_node_at_offset::<ast::MethodCallExpr>(syntax, offset) {
+            return Some(FnCallNode::MethodCallExpr(expr));
+        }
+        None
+    }
+
+    pub fn name_ref(&self) -> Option<&'a ast::NameRef> {
+        match *self {
+            FnCallNode::CallExpr(call_expr) => Some(match call_expr.expr()?.kind() {
+                ast::ExprKind::PathExpr(path_expr) => path_expr.path()?.segment()?.name_ref()?,
+                _ => return None,
+            }),
+
+            FnCallNode::MethodCallExpr(call_expr) => call_expr
+                .syntax()
+                .children()
+                .filter_map(ast::NameRef::cast)
+                .nth(0),
+        }
+    }
+
+    pub fn arg_list(&self) -> Option<&'a ast::ArgList> {
+        match *self {
+            FnCallNode::CallExpr(expr) => expr.arg_list(),
+            FnCallNode::MethodCallExpr(expr) => expr.arg_list(),
+        }
+    }
+}