Upgrade to rust edition 2021

Cargo.toml

@@ -5,3 +5,4 @@ members = [
     "rcdom",
     "xml5ever"
 ]
+resolver = "2"

html5ever/Cargo.toml

@@ -9,7 +9,7 @@ description = "High-performance browser-grade HTML5 parser"
 documentation = "https://docs.rs/html5ever"
 build = "build.rs"
 categories = [ "parser-implementations", "web-programming" ]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 log = "0.4"

html5ever/src/tree_builder/mod.rs

@@ -261,7 +261,7 @@ where
 
     /// Call the `Tracer`'s `trace_handle` method on every `Handle` in the tree builder's
     /// internal state.  This is intended to support garbage-collected DOMs.
-    pub fn trace_handles(&self, tracer: &Tracer<Handle = Handle>) {
+    pub fn trace_handles(&self, tracer: &dyn Tracer<Handle = Handle>) {
         tracer.trace_handle(&self.doc_handle);
         for e in &self.open_elems {
             tracer.trace_handle(e);

markup5ever/Cargo.toml

@@ -8,7 +8,7 @@ description = "Common code for xml5ever and html5ever"
 documentation = "https://docs.rs/markup5ever"
 build = "build.rs"
 categories = [ "parser-implementations", "web-programming" ]
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"

rcdom/Cargo.toml

@@ -8,7 +8,7 @@ description = "Basic, unsupported DOM structure for use by tests in html5ever/xm
 readme = "README.md"
 documentation = "https://docs.rs/markup5ever_rcdom"
 categories = [ "parser-implementations", "web-programming" ]
-edition = "2018"
+edition = "2021"
 publish = false
 
 [lib]

xml5ever/Cargo.toml

@@ -13,7 +13,7 @@ readme = "README.md"
 keywords = ["xml", "xml5", "parser", "parsing"]
 exclude = ["xml5lib-tests/*"]
 categories = [ "parser-implementations", "web-programming" ]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 log = "0.4"