Language Server: textDocument/signatureHelp

Implements a pretty barebones function signature help mechanism in
the language server.

Users can use `Analysis::resolve_callback()` to get basic information
about a call site.

Fixes #102

2 files changed, 5 insertions, 2 deletions

diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index ef7b5b1a1..1901a667c 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -1387,7 +1387,10 @@ impl<'a> AstNode<'a> for PathExpr<'a> {
     fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
 }
 
-impl<'a> PathExpr<'a> {}
+impl<'a> PathExpr<'a> {pub fn path(self) -> Option<Path<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // PathPat
 #[derive(Debug, Clone, Copy)]
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 9da0c2c13..a904f7505 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -342,7 +342,7 @@ Grammar(
         "TupleExpr": (),
         "ArrayExpr": (),
         "ParenExpr": (),
-        "PathExpr": (),
+        "PathExpr": (options: ["Path"]),
         "LambdaExpr": (
             options: [
                 "ParamList",