fix code duplication

crates/ra_ide_api_light/src/formatting.rs

@@ -0,0 +1,42 @@
+use ra_syntax::{
+    ast, AstNode,
+    SyntaxNode, SyntaxKind::*,
+};
+
+pub(crate) fn extract_trivial_expression(block: &ast::Block) -> Option<&ast::Expr> {
+    let expr = block.expr()?;
+    if expr.syntax().text().contains('\n') {
+        return None;
+    }
+    let non_trivial_children = block.syntax().children().filter(|it| match it.kind() {
+        WHITESPACE | L_CURLY | R_CURLY => false,
+        _ => it != &expr.syntax(),
+    });
+    if non_trivial_children.count() > 0 {
+        return None;
+    }
+    Some(expr)
+}
+
+pub(crate) fn compute_ws(left: &SyntaxNode, right: &SyntaxNode) -> &'static str {
+    match left.kind() {
+        L_PAREN | L_BRACK => return "",
+        L_CURLY => {
+            if let USE_TREE = right.kind() {
+                return "";
+            }
+        }
+        _ => (),
+    }
+    match right.kind() {
+        R_PAREN | R_BRACK => return "",
+        R_CURLY => {
+            if let USE_TREE = left.kind() {
+                return "";
+            }
+        }
+        DOT => return "",
+        _ => (),
+    }
+    " "
+}