Auto merge of #114104 - oli-obk:syn2, r=compiler-errors

Lots of tiny incremental simplifications of `EmitterWriter` internals

ignore the first commit, it's https://github.com/rust-lang/rust/pull/114088 squashed and rebased, but it's needed to use to use `derive_setters`, as they need a newer `syn` version.

Then this PR starts out with removing many arguments that are almost always defaulted to `None` or `false` and replace them with builder methods that can set these fields in the few cases that want to set them.

After that it's one commit after the other that removes or merges things until everything becomes some very simple trait objects

compiler/rustc_expand/Cargo.toml

@@ -27,3 +27,4 @@ rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 thin-vec = "0.2.12"
 tracing = "0.1"
+termcolor = "1.2"

compiler/rustc_expand/src/tests.rs

@@ -8,7 +8,8 @@ use rustc_span::{BytePos, Span};
 
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::emitter::EmitterWriter;
-use rustc_errors::{Handler, MultiSpan, PResult, TerminalUrl};
+use rustc_errors::{Handler, MultiSpan, PResult};
+use termcolor::WriteColor;
 
 use std::io;
 use std::io::prelude::*;
@@ -29,19 +30,9 @@ fn create_test_handler() -> (Handler, Lrc<SourceMap>, Arc<Mutex<Vec<u8>>>) {
         vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
         false,
     );
-    let emitter = EmitterWriter::new(
-        Box::new(Shared { data: output.clone() }),
-        Some(source_map.clone()),
-        None,
-        fallback_bundle,
-        false,
-        false,
-        false,
-        Some(140),
-        false,
-        false,
-        TerminalUrl::No,
-    );
+    let emitter = EmitterWriter::new(Box::new(Shared { data: output.clone() }), fallback_bundle)
+        .sm(Some(source_map.clone()))
+        .diagnostic_width(Some(140));
     let handler = Handler::with_emitter(Box::new(emitter));
     (handler, source_map, output)
 }
@@ -165,6 +156,20 @@ pub(crate) struct Shared<T: Write> {
     pub data: Arc<Mutex<T>>,
 }
 
+impl<T: Write> WriteColor for Shared<T> {
+    fn supports_color(&self) -> bool {
+        false
+    }
+
+    fn set_color(&mut self, _spec: &termcolor::ColorSpec) -> io::Result<()> {
+        Ok(())
+    }
+
+    fn reset(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
 impl<T: Write> Write for Shared<T> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         self.data.lock().unwrap().write(buf)