Rollup merge of #142856 - cjgillot:inline-serialize, r=petrochenkov

Add a few inline directives in rustc_serialize.

I see `debug_strict_add` and `debug_strict_sub` appearing in callgrind output. This bothers me. This PR should make them disappear.

Author: GuillaumeGomez

compiler/rustc_serialize/src/int_overflow.rs

@@ -20,6 +20,7 @@ macro_rules! impl_debug_strict_add {
     ($( $ty:ty )*) => {
         $(
             impl DebugStrictAdd for $ty {
+                #[inline]
                 fn debug_strict_add(self, other: Self) -> Self {
                     if cfg!(debug_assertions) {
                         self + other
@@ -42,6 +43,7 @@ macro_rules! impl_debug_strict_sub {
     ($( $ty:ty )*) => {
         $(
             impl DebugStrictSub for $ty {
+                #[inline]
                 fn debug_strict_sub(self, other: Self) -> Self {
                     if cfg!(debug_assertions) {
                         self - other

compiler/rustc_serialize/src/opaque.rs

@@ -89,10 +89,12 @@ impl FileEncoder {
         self.buffered = 0;
     }
 
+    #[inline]
     pub fn file(&self) -> &File {
         &self.file
     }
 
+    #[inline]
     pub fn path(&self) -> &Path {
         &self.path
     }