Rollup merge of #138111 - estebank:use-dfv, r=nnethercote

Use `default_field_values` for `rustc_errors::Context`, `rustc_session::config::NextSolverConfig` and `rustc_session::config::ErrorOutputType`

Wanted to see  where `#![feature(default_field_values)]` could be used in the codebase. These three seemed like no-brainers. There are a bunch of more places where we could remove manual `Default` impls, but they `derive` other traits that rely on `syn`, which [doesn't yet support `default_field_values`](dtolnay/syn#1774).

Author: matthiaskrgr

Diff for: compiler/rustc_errors/src/lib.rs

@@ -14,6 +14,7 @@
 #![feature(associated_type_defaults)]
 #![feature(box_into_inner)]
 #![feature(box_patterns)]
+#![feature(default_field_values)]
 #![feature(error_reporter)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]

Diff for: compiler/rustc_errors/src/markdown/parse.rs

@@ -40,11 +40,13 @@ type ParseResult<'a> = Option<Parsed<'a>>;
 
 /// Parsing context
 #[derive(Clone, Copy, Debug, PartialEq)]
+// The default values are the most common setting for non top-level parsing: not top block, not at
+// line start (yes leading whitespace, not escaped).
 struct Context {
     /// If true, we are at a the topmost level (not recursing a nested tt)
-    top_block: bool,
+    top_block: bool = false,
     /// Previous character
-    prev: Prev,
+    prev: Prev = Prev::Whitespace,
 }
 
 /// Character class preceding this one
@@ -57,14 +59,6 @@ enum Prev {
     Any,
 }
 
-impl Default for Context {
-    /// Most common setting for non top-level parsing: not top block, not at
-    /// line start (yes leading whitespace, not escaped)
-    fn default() -> Self {
-        Self { top_block: false, prev: Prev::Whitespace }
-    }
-}
-
 /// Flags to simple parser function
 #[derive(Clone, Copy, Debug, PartialEq)]
 enum ParseOpt {
@@ -248,7 +242,7 @@ fn parse_heading(buf: &[u8]) -> ParseResult<'_> {
     }
 
     let (txt, rest) = parse_to_newline(&buf[1..]);
-    let ctx = Context { top_block: false, prev: Prev::Whitespace };
+    let ctx = Context { .. };
     let stream = parse_recursive(txt, ctx);
 
     Some((MdTree::Heading(level.try_into().unwrap(), stream), rest))
@@ -257,7 +251,7 @@ fn parse_heading(buf: &[u8]) -> ParseResult<'_> {
 /// Bulleted list
 fn parse_unordered_li(buf: &[u8]) -> Parsed<'_> {
     let (txt, rest) = get_indented_section(&buf[2..]);
-    let ctx = Context { top_block: false, prev: Prev::Whitespace };
+    let ctx = Context { .. };
     let stream = parse_recursive(trim_ascii_start(txt), ctx);
     (MdTree::UnorderedListItem(stream), rest)
 }
@@ -266,7 +260,7 @@ fn parse_unordered_li(buf: &[u8]) -> Parsed<'_> {
 fn parse_ordered_li(buf: &[u8]) -> Parsed<'_> {
     let (num, pos) = ord_list_start(buf).unwrap(); // success tested in caller
     let (txt, rest) = get_indented_section(&buf[pos..]);
-    let ctx = Context { top_block: false, prev: Prev::Whitespace };
+    let ctx = Context { .. };
     let stream = parse_recursive(trim_ascii_start(txt), ctx);
     (MdTree::OrderedListItem(num, stream), rest)
 }

Diff for: compiler/rustc_session/src/config.rs

@@ -681,10 +681,14 @@ impl OutputType {
 }
 
 /// The type of diagnostics output to generate.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
 pub enum ErrorOutputType {
     /// Output meant for the consumption of humans.
-    HumanReadable(HumanReadableErrorType, ColorConfig),
+    #[default]
+    HumanReadable {
+        kind: HumanReadableErrorType = HumanReadableErrorType::Default,
+        color_config: ColorConfig = ColorConfig::Auto,
+    },
     /// Output that's consumed by other tools such as `rustfix` or the `RLS`.
     Json {
         /// Render the JSON in a human readable way (with indents and newlines).
@@ -696,12 +700,6 @@ pub enum ErrorOutputType {
     },
 }
 
-impl Default for ErrorOutputType {
-    fn default() -> Self {
-        Self::HumanReadable(HumanReadableErrorType::Default, ColorConfig::Auto)
-    }
-}
-
 #[derive(Clone, Hash, Debug)]
 pub enum ResolveDocLinks {
     /// Do not resolve doc links.
@@ -898,18 +896,13 @@ pub enum PrintKind {
     DeploymentTarget,
 }
 
-#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, Default)]
 pub struct NextSolverConfig {
     /// Whether the new trait solver should be enabled in coherence.
-    pub coherence: bool,
+    pub coherence: bool = true,
     /// Whether the new trait solver should be enabled everywhere.
     /// This is only `true` if `coherence` is also enabled.
-    pub globally: bool,
-}
-impl Default for NextSolverConfig {
-    fn default() -> Self {
-        NextSolverConfig { coherence: true, globally: false }
-    }
+    pub globally: bool = false,
 }
 
 #[derive(Clone)]
@@ -1825,7 +1818,7 @@ pub fn parse_json(early_dcx: &EarlyDiagCtxt, matches: &getopts::Matches) -> Json
 pub fn parse_error_format(
     early_dcx: &mut EarlyDiagCtxt,
     matches: &getopts::Matches,
-    color: ColorConfig,
+    color_config: ColorConfig,
     json_color: ColorConfig,
     json_rendered: HumanReadableErrorType,
 ) -> ErrorOutputType {
@@ -1835,35 +1828,34 @@ pub fn parse_error_format(
     // `opt_present` because the latter will panic.
     let error_format = if matches.opts_present(&["error-format".to_owned()]) {
         match matches.opt_str("error-format").as_deref() {
-            None | Some("human") => {
-                ErrorOutputType::HumanReadable(HumanReadableErrorType::Default, color)
-            }
-            Some("human-annotate-rs") => {
-                ErrorOutputType::HumanReadable(HumanReadableErrorType::AnnotateSnippet, color)
-            }
+            None | Some("human") => ErrorOutputType::HumanReadable { color_config, .. },
+            Some("human-annotate-rs") => ErrorOutputType::HumanReadable {
+                kind: HumanReadableErrorType::AnnotateSnippet,
+                color_config,
+            },
             Some("json") => {
                 ErrorOutputType::Json { pretty: false, json_rendered, color_config: json_color }
             }
             Some("pretty-json") => {
                 ErrorOutputType::Json { pretty: true, json_rendered, color_config: json_color }
             }
-            Some("short") => ErrorOutputType::HumanReadable(HumanReadableErrorType::Short, color),
-            Some("human-unicode") => {
-                ErrorOutputType::HumanReadable(HumanReadableErrorType::Unicode, color)
+            Some("short") => {
+                ErrorOutputType::HumanReadable { kind: HumanReadableErrorType::Short, color_config }
             }
+            Some("human-unicode") => ErrorOutputType::HumanReadable {
+                kind: HumanReadableErrorType::Unicode,
+                color_config,
+            },
             Some(arg) => {
-                early_dcx.set_error_format(ErrorOutputType::HumanReadable(
-                    HumanReadableErrorType::Default,
-                    color,
-                ));
+                early_dcx.set_error_format(ErrorOutputType::HumanReadable { color_config, .. });
                 early_dcx.early_fatal(format!(
                     "argument for `--error-format` must be `human`, `human-annotate-rs`, \
                     `human-unicode`, `json`, `pretty-json` or `short` (instead was `{arg}`)"
                 ))
             }
         }
     } else {
-        ErrorOutputType::HumanReadable(HumanReadableErrorType::Default, color)
+        ErrorOutputType::HumanReadable { color_config, .. }
     };
 
     match error_format {
@@ -1918,7 +1910,7 @@ fn check_error_format_stability(
     }
     let format = match format {
         ErrorOutputType::Json { pretty: true, .. } => "pretty-json",
-        ErrorOutputType::HumanReadable(format, _) => match format {
+        ErrorOutputType::HumanReadable { kind, .. } => match kind {
             HumanReadableErrorType::AnnotateSnippet => "human-annotate-rs",
             HumanReadableErrorType::Unicode => "human-unicode",
             _ => return,

Diff for: compiler/rustc_session/src/lib.rs

@@ -1,5 +1,6 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
+#![feature(default_field_values)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
 #![feature(rustc_attrs)]

Diff for: compiler/rustc_session/src/session.rs

@@ -913,7 +913,7 @@ fn default_emitter(
     let source_map = if sopts.unstable_opts.link_only { None } else { Some(source_map) };
 
     match sopts.error_format {
-        config::ErrorOutputType::HumanReadable(kind, color_config) => {
+        config::ErrorOutputType::HumanReadable { kind, color_config } => {
             let short = kind.short();
 
             if let HumanReadableErrorType::AnnotateSnippet = kind {
@@ -1430,7 +1430,7 @@ fn mk_emitter(output: ErrorOutputType) -> Box<DynEmitter> {
     let fallback_bundle =
         fallback_fluent_bundle(vec![rustc_errors::DEFAULT_LOCALE_RESOURCE], false);
     let emitter: Box<DynEmitter> = match output {
-        config::ErrorOutputType::HumanReadable(kind, color_config) => {
+        config::ErrorOutputType::HumanReadable { kind, color_config } => {
             let short = kind.short();
             Box::new(
                 HumanEmitter::new(stderr_destination(color_config), fallback_bundle)

Diff for: src/librustdoc/core.rs

@@ -154,7 +154,7 @@ pub(crate) fn new_dcx(
         false,
     );
     let emitter: Box<DynEmitter> = match error_format {
-        ErrorOutputType::HumanReadable(kind, color_config) => {
+        ErrorOutputType::HumanReadable { kind, color_config } => {
             let short = kind.short();
             Box::new(
                 HumanEmitter::new(stderr_destination(color_config), fallback_bundle)

Diff for: src/librustdoc/doctest.rs

@@ -580,7 +580,7 @@ fn run_test(
             path_for_rustdoc.to_str().expect("target path must be valid unicode")
         }
     });
-    if let ErrorOutputType::HumanReadable(kind, color_config) = rustdoc_options.error_format {
+    if let ErrorOutputType::HumanReadable { kind, color_config } = rustdoc_options.error_format {
         let short = kind.short();
         let unicode = kind == HumanReadableErrorType::Unicode;