Extract method

Author: phansch

clippy_lints/src/explicit_write.rs

@@ -51,15 +51,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
             if unwrap_args.len() > 0;
             if let ExprKind::MethodCall(ref write_fun, _, ref write_args) =
                 unwrap_args[0].node;
-            // Obtain the string that should be printed
-            if write_args.len() > 1;
-            if let ExprKind::Call(_, ref output_args) = write_args[1].node;
-            if output_args.len() > 0;
-            if let ExprKind::AddrOf(_, ref output_string_expr) = output_args[0].node;
-            if let ExprKind::Array(ref string_exprs) = output_string_expr.node;
-            if string_exprs.len() > 0;
-            if let ExprKind::Lit(ref lit) = string_exprs[0].node;
-            if let LitKind::Str(ref write_output, _) = lit.node;
             if write_fun.ident.name == "write_fmt";
             // match calls to std::io::stdout() / std::io::stderr ()
             if write_args.len() > 0;
@@ -94,7 +85,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
                 // We need to remove the last trailing newline from the string because the
                 // underlying `fmt::write` function doesn't know wether `println!` or `print!` was
                 // used.
-                let mut write_output: String = write_output.to_string();
+                let mut write_output: String = write_output_string(write_args).unwrap();
                 if write_output.ends_with('\n') {
                     write_output.truncate(write_output.len() - 1)
                 }
@@ -125,3 +116,22 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
         }
     }
 }
+
+// Extract the output string from the given `write_args`.
+fn write_output_string(write_args: &HirVec<Expr>) -> Option<String> {
+    if_chain! {
+        // Obtain the string that should be printed
+        if write_args.len() > 1;
+        if let ExprKind::Call(_, ref output_args) = write_args[1].node;
+        if output_args.len() > 0;
+        if let ExprKind::AddrOf(_, ref output_string_expr) = output_args[0].node;
+        if let ExprKind::Array(ref string_exprs) = output_string_expr.node;
+        if string_exprs.len() > 0;
+        if let ExprKind::Lit(ref lit) = string_exprs[0].node;
+        if let LitKind::Str(ref write_output, _) = lit.node;
+        then {
+            return Some(write_output.to_string())
+        }
+    }
+    None
+}