Remove yet more string allocations (#759)

Author: reese

librubyfmt/src/format.rs

@@ -1172,16 +1172,16 @@ pub fn format_paren(ps: &mut ParserState, paren: ParenExpr) {
 }
 
 pub fn format_dot2(ps: &mut ParserState, dot2: Dot2) {
-    format_dot2_or_3(ps, "..".to_string(), dot2.1, dot2.2);
+    format_dot2_or_3(ps, "..", dot2.1, dot2.2);
 }
 
 pub fn format_dot3(ps: &mut ParserState, dot3: Dot3) {
-    format_dot2_or_3(ps, "...".to_string(), dot3.1, dot3.2);
+    format_dot2_or_3(ps, "...", dot3.1, dot3.2);
 }
 
 pub fn format_dot2_or_3(
     ps: &mut ParserState,
-    dots: String,
+    dots: &'static str,
     left: Option<Box<Expression>>,
     right: Option<Box<Expression>>,
 ) {
@@ -1206,12 +1206,12 @@ pub fn format_dot2_or_3(
     }
 }
 
-pub fn percent_symbol_for(tag: String) -> String {
+pub fn percent_symbol_for(tag: String) -> &'static str {
     match tag.as_ref() {
-        "qsymbols" => "%i".to_string(),
-        "qwords" => "%w".to_string(),
-        "symbols" => "%I".to_string(),
-        "words" => "%W".to_string(),
+        "qsymbols" => "%i",
+        "qwords" => "%w",
+        "symbols" => "%I",
+        "words" => "%W",
         _ => panic!("got invalid percent symbol"),
     }
 }

librubyfmt/src/format_prism.rs

@@ -2164,7 +2164,7 @@ fn format_call_chain_segments<'src>(
         // Attr_write values are formatted after the breakable so they break independently
         if let Some(value) = trailing_attr_write_value {
             ps.emit_space();
-            ps.emit_op("=".to_string());
+            ps.emit_op("=");
             ps.emit_space();
             ps.with_start_of_line(false, |ps| format_node(ps, value));
         }
@@ -2728,7 +2728,7 @@ fn format_array_node<'src>(ps: &mut ParserState<'src>, array_node: prism::ArrayN
     let orig_delim = opening.and_then(|s| s.chars().nth(2)).unwrap_or('[');
 
     if is_word_array {
-        ps.emit_ident(opening.unwrap().split_at(2).0.to_string());
+        ps.emit_ident(opening.unwrap().split_at(2).0);
     }
 
     if array_node.elements().is_empty() {

librubyfmt/src/string_escape.rs

@@ -27,7 +27,7 @@ pub fn single_to_double_quoted(content: &str, start_delim: &str, end_delim: &str
             .replace_all(content, |captures: &fancy_regex::Captures| {
                 // first capture is the entire match
                 let val = captures.get(0).unwrap();
-                let val_str = val.as_str().to_string();
+                let val_str = val.as_str();
                 if val_str.ends_with("\"") {
                     // Ends with a quote, which we transform to `\"`
                     format!("{}\\\"", &val_str[0..(val_str.len() - 1)])