Auto merge of #18355 - servo:no-fmt, r=emilio

Reduce usage of fmt in serialization and error reporting

`format!` and `write!` create a somewhat-heavyweight `Formatting` struct and use dynamic dispatch to call into impls of `Dispaly` and related traits. The former also allocates an intermediate string that is sometimes unnecessary.

I started looking into this from https://bugzilla.mozilla.org/show_bug.cgi?id=1355599, but I expect the impact there will be small to insignificant. It might be a slightly less so on parsing (error reporting).

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tests/unit/style/rule_tree/bench.rs

@@ -22,7 +22,7 @@ impl ParseErrorReporter for ErrorringErrorReporter {
                     url: &ServoUrl,
                     location: SourceLocation,
                     error: ContextualParseError) {
-        panic!("CSS error: {}\t\n{}:{} {}", url.as_str(), location.line, location.column, error.to_string());
+        panic!("CSS error: {}\t\n{}:{} {}", url.as_str(), location.line, location.column, error);
     }
 }
 

tests/unit/style/stylesheets.rs

@@ -280,7 +280,7 @@ impl ParseErrorReporter for CSSInvalidErrorReporterTest {
                 url: url.clone(),
                 line: location.line,
                 column: location.column,
-                message: error.to_string()
+                message: error.to_string(),
             }
         );
     }

tests/unit/style/viewport.rs

@@ -11,7 +11,7 @@ use servo_config::prefs::{PREFS, PrefValue};
 use servo_url::ServoUrl;
 use style::context::QuirksMode;
 use style::media_queries::{Device, MediaList, MediaType};
-use style::parser::{Parse, ParserContext, ParserErrorContext};
+use style::parser::{ParserContext, ParserErrorContext};
 use style::shared_lock::SharedRwLock;
 use style::stylesheets::{CssRuleType, Stylesheet, StylesheetInDocument, Origin};
 use style::stylesheets::viewport_rule::*;

tests/unit/stylo/lib.rs

@@ -12,7 +12,6 @@ extern crate selectors;
 #[macro_use] extern crate style;
 extern crate style_traits;
 
-mod sanity_checks;
 #[cfg(target_pointer_width = "64")]
 mod size_of;
 mod specified_values;

tests/unit/stylo/sanity_checks.rs

@@ -1,28 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-//! Different static asserts that ensure the build does what it's expected to.
-//!
-//! TODO: maybe cfg(test) this?
-
-#![allow(unused_imports)]
-
-use std::mem;
-
-macro_rules! check_enum_value {
-    ($a:expr, $b:expr) => {
-        unsafe {
-            mem::transmute::<[u32; $a as usize],
-                             [u32; $b as usize]>([0; $a as usize]);
-        }
-    }
-}
-
-// NB: It's a shame we can't do this statically with bitflags, but no
-// const-fn and no other way to access the numerical value :-(
-macro_rules! check_enum_value_non_static {
-    ($a:expr, $b:expr) => {
-        assert_eq!($a.0 as usize, $b as usize);
-    }
-}

tests/unit/stylo/specified_values.rs

@@ -5,6 +5,7 @@
 use style;
 
 #[cfg(all(test, target_pointer_width = "64"))]
+#[test]
 fn size_of_specified_values() {
     use std::mem::size_of;
     let threshold = 24;

tests/wpt/mozilla/meta/MANIFEST.json

@@ -26530,7 +26530,7 @@
    "testharness"
   ],
   "mozilla/calc.html": [
-   "5b3ea33205a9f2404bd6976a2c7f6fc451be8e96",
+   "4f65929cacf623da2d3e310a6663d6165a1b0cdc",
    "testharness"
   ],
   "mozilla/canvas.initial.reset.2dstate.html": [

tests/wpt/mozilla/tests/mozilla/calc.html

@@ -42,7 +42,7 @@ var widthTests = [
     ['calc(10px + 10em - 10px)', 'calc(10em + 0px)', '160px'],
 
     // Fold absolute units
-    ['calc(1px + 1pt + 1pc + 1in + 1cm + 1mm)', 'calc(155.91666666666666px)', '155.91666666666666px'],
+    ['calc(96px + 72pt + 6pc + 1in + 2.54cm + 25.4mm)', 'calc(576px)', '576px'],
 
     // Alphabetical order
     ['calc(0ch + 0px + 0pt + 0pc + 0in + 0cm + 0mm + 0rem + 0em + 0ex + 0% + 0vw + 0vh + 0vmin + 0vmax)',