Refactor CallInfo function signatures to new FunctionSignature type

This is used by CallInfo to create a pretty printed function signature that can
be used with completions and other places as well.

crates/ra_ide_api/src/lib.rs

@@ -37,6 +37,7 @@ mod join_lines;
 mod structure;
 mod typing;
 mod matching_brace;
+mod display;
 
 #[cfg(test)]
 mod marks;
@@ -243,12 +244,36 @@ impl<T> RangeInfo<T> {
 
 #[derive(Debug)]
 pub struct CallInfo {
-    pub label: String,
-    pub doc: Option<Documentation>,
-    pub parameters: Vec<String>,
+    pub signature: FunctionSignature,
     pub active_parameter: Option<usize>,
 }
 
+/// Contains information about a function signature
+#[derive(Debug)]
+pub struct FunctionSignature {
+    /// Optional visibility
+    pub visibility: Option<String>,
+    /// Name of the function
+    pub name: Option<String>,
+    /// Documentation for the function
+    pub doc: Option<Documentation>,
+    /// Generic parameters
+    pub generic_parameters: Vec<String>,
+    /// Parameters of the function
+    pub parameters: Vec<String>,
+    /// Optional return type
+    pub ret_type: Option<String>,
+    /// Where predicates
+    pub where_predicates: Vec<String>,
+}
+
+impl FunctionSignature {
+    pub(crate) fn with_doc_opt(mut self, doc: Option<Documentation>) -> Self {
+        self.doc = doc;
+        self
+    }
+}
+
 /// `AnalysisHost` stores the current state of the world.
 #[derive(Debug, Default)]
 pub struct AnalysisHost {