Move `IntoDiagArg` earlier in the dependency chains

`rustc_errors` depends on numerous crates, solely to implement its
`IntoDiagArg` trait on types from those crates. Many crates depend on
`rustc_errors`, and it's on the critical path.

We can't swap things around to make all of those crates depend on
`rustc_errors` instead, because `rustc_errors` would end up in
dependency cycles.

Instead, move `IntoDiagArg` into `rustc_error_messages`, which has far
fewer dependencies, and then have most of these crates depend on
`rustc_error_messages`.

This allows `rustc_errors` to drop dependencies on several crates,
including the large `rustc_target`.

(This doesn't fully reduce dependency chains yet, as `rustc_errors`
still depends on `rustc_hir` which depends on `rustc_target`. That will
get fixed in a subsequent commit.)

4 files changed, 19 insertions, 379 deletions

diff --git a/compiler/rustc_errors/src/codes.rs b/compiler/rustc_errors/src/codes.rs
index 947cf27ca79..787a8af99b1 100644
--- a/compiler/rustc_errors/src/codes.rs
+++ b/compiler/rustc_errors/src/codes.rs
@@ -20,6 +20,8 @@ impl fmt::Display for ErrCode {
     }
 }
 
+rustc_error_messages::into_diag_arg_using_display!(ErrCode);
+
 macro_rules! define_error_code_constants_and_diagnostics_table {
     ($($name:ident: $num:literal,)*) => (
         $(
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index e579370ce4e..183dceddd2c 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -8,7 +8,7 @@ use std::path::PathBuf;
 use std::thread::panicking;
 
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_error_messages::{FluentValue, fluent_value_from_str_list_sep_by_and};
+use rustc_error_messages::{DiagArgName, DiagArgValue, IntoDiagArg};
 use rustc_lint_defs::{Applicability, LintExpectationId};
 use rustc_macros::{Decodable, Encodable};
 use rustc_span::source_map::Spanned;
@@ -22,26 +22,6 @@ use crate::{
     Suggestions,
 };
 
-/// Simplified version of `FluentArg` that can implement `Encodable` and `Decodable`. Collection of
-/// `DiagArg` are converted to `FluentArgs` (consuming the collection) at the start of diagnostic
-/// emission.
-pub type DiagArg<'iter> = (&'iter DiagArgName, &'iter DiagArgValue);
-
-/// Name of a diagnostic argument.
-pub type DiagArgName = Cow<'static, str>;
-
-/// Simplified version of `FluentValue` that can implement `Encodable` and `Decodable`. Converted
-/// to a `FluentValue` by the emitter to be used in diagnostic translation.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
-pub enum DiagArgValue {
-    Str(Cow<'static, str>),
-    // This gets converted to a `FluentNumber`, which is an `f64`. An `i32`
-    // safely fits in an `f64`. Any integers bigger than that will be converted
-    // to strings in `into_diag_arg` and stored using the `Str` variant.
-    Number(i32),
-    StrListSepByAnd(Vec<Cow<'static, str>>),
-}
-
 pub type DiagArgMap = FxIndexMap<DiagArgName, DiagArgValue>;
 
 /// Trait for types that `Diag::emit` can return as a "guarantee" (or "proof")
@@ -143,36 +123,6 @@ where
     }
 }
 
-/// Converts a value of a type into a `DiagArg` (typically a field of an `Diag` struct).
-/// Implemented as a custom trait rather than `From` so that it is implemented on the type being
-/// converted rather than on `DiagArgValue`, which enables types from other `rustc_*` crates to
-/// implement this.
-pub trait IntoDiagArg {
-    /// Convert `Self` into a `DiagArgValue` suitable for rendering in a diagnostic.
-    ///
-    /// It takes a `path` where "long values" could be written to, if the `DiagArgValue` is too big
-    /// for displaying on the terminal. This path comes from the `Diag` itself. When rendering
-    /// values that come from `TyCtxt`, like `Ty<'_>`, they can use `TyCtxt::short_string`. If a
-    /// value has no shortening logic that could be used, the argument can be safely ignored.
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue;
-}
-
-impl IntoDiagArg for DiagArgValue {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self
-    }
-}
-
-impl From<DiagArgValue> for FluentValue<'static> {
-    fn from(val: DiagArgValue) -> Self {
-        match val {
-            DiagArgValue::Str(s) => From::from(s),
-            DiagArgValue::Number(n) => From::from(n),
-            DiagArgValue::StrListSepByAnd(l) => fluent_value_from_str_list_sep_by_and(l),
-        }
-    }
-}
-
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
 /// `#[derive(Subdiagnostic)]` -- see [rustc_macros::Subdiagnostic].
 #[rustc_diagnostic_item = "Subdiagnostic"]
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 698b6b8d504..435d16a8380 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -1,340 +1,22 @@
-use std::backtrace::Backtrace;
 use std::borrow::Cow;
-use std::fmt;
-use std::num::ParseIntError;
-use std::path::{Path, PathBuf};
-use std::process::ExitStatus;
 
 use rustc_abi::TargetDataLayoutErrors;
-use rustc_ast::util::parser::ExprPrecedence;
-use rustc_ast_pretty::pprust;
-use rustc_hir::RustcVersion;
-use rustc_hir::attrs::{MirDialect, MirPhase};
+use rustc_error_messages::{DiagArgValue, IntoDiagArg};
 use rustc_macros::Subdiagnostic;
-use rustc_span::edition::Edition;
-use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol};
-use rustc_target::spec::{PanicStrategy, SplitDebuginfo, StackProtector, TargetTuple};
-use rustc_type_ir::{ClosureKind, FloatTy};
-use {rustc_ast as ast, rustc_hir as hir};
+use rustc_span::{Span, Symbol};
 
 use crate::diagnostic::DiagLocation;
 use crate::{
-    Diag, DiagArgValue, DiagCtxtHandle, Diagnostic, EmissionGuarantee, ErrCode, IntoDiagArg, Level,
-    Subdiagnostic, fluent_generated as fluent,
+    Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level, Subdiagnostic,
+    fluent_generated as fluent,
 };
 
-pub struct DiagArgFromDisplay<'a>(pub &'a dyn fmt::Display);
-
-impl IntoDiagArg for DiagArgFromDisplay<'_> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.0.to_string().into_diag_arg(path)
-    }
-}
-
-impl<'a> From<&'a dyn fmt::Display> for DiagArgFromDisplay<'a> {
-    fn from(t: &'a dyn fmt::Display) -> Self {
-        DiagArgFromDisplay(t)
-    }
-}
-
-impl<'a, T: fmt::Display> From<&'a T> for DiagArgFromDisplay<'a> {
-    fn from(t: &'a T) -> Self {
-        DiagArgFromDisplay(t)
-    }
-}
-
-impl<'a, T: Clone + IntoDiagArg> IntoDiagArg for &'a T {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.clone().into_diag_arg(path)
-    }
-}
-
-#[macro_export]
-macro_rules! into_diag_arg_using_display {
-    ($( $ty:ty ),+ $(,)?) => {
-        $(
-            impl IntoDiagArg for $ty {
-                fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-                    self.to_string().into_diag_arg(path)
-                }
-            }
-        )+
-    }
-}
-
-macro_rules! into_diag_arg_for_number {
-    ($( $ty:ty ),+ $(,)?) => {
-        $(
-            impl IntoDiagArg for $ty {
-                fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-                    // Convert to a string if it won't fit into `Number`.
-                    #[allow(irrefutable_let_patterns)]
-                    if let Ok(n) = TryInto::<i32>::try_into(self) {
-                        DiagArgValue::Number(n)
-                    } else {
-                        self.to_string().into_diag_arg(path)
-                    }
-                }
-            }
-        )+
-    }
-}
-
-into_diag_arg_using_display!(
-    ast::ParamKindOrd,
-    std::io::Error,
-    Box<dyn std::error::Error>,
-    std::num::NonZero<u32>,
-    hir::Target,
-    Edition,
-    Ident,
-    MacroRulesNormalizedIdent,
-    ParseIntError,
-    StackProtector,
-    &TargetTuple,
-    SplitDebuginfo,
-    ExitStatus,
-    ErrCode,
-    rustc_abi::ExternAbi,
-);
-
-impl IntoDiagArg for RustcVersion {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.to_string()))
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::TraitRef<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_string().into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::ExistentialTraitRef<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_string().into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::UnevaluatedConst<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        format!("{self:?}").into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner> IntoDiagArg for rustc_type_ir::FnSig<I> {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        format!("{self:?}").into_diag_arg(path)
-    }
-}
-
-impl<I: rustc_type_ir::Interner, T> IntoDiagArg for rustc_type_ir::Binder<I, T>
-where
-    T: IntoDiagArg,
-{
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.skip_binder().into_diag_arg(path)
-    }
-}
-
-into_diag_arg_for_number!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
-
-impl IntoDiagArg for bool {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        if self {
-            DiagArgValue::Str(Cow::Borrowed("true"))
-        } else {
-            DiagArgValue::Str(Cow::Borrowed("false"))
-        }
-    }
-}
-
-impl IntoDiagArg for char {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(format!("{self:?}")))
-    }
-}
-
-impl IntoDiagArg for Vec<char> {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::StrListSepByAnd(
-            self.into_iter().map(|c| Cow::Owned(format!("{c:?}"))).collect(),
-        )
-    }
-}
-
-impl IntoDiagArg for Symbol {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_ident_string().into_diag_arg(path)
-    }
-}
-
-impl<'a> IntoDiagArg for &'a str {
-    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        self.to_string().into_diag_arg(path)
-    }
-}
-
-impl IntoDiagArg for String {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self))
-    }
-}
-
-impl<'a> IntoDiagArg for Cow<'a, str> {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.into_owned()))
-    }
-}
-
-impl<'a> IntoDiagArg for &'a Path {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.display().to_string()))
-    }
-}
-
-impl IntoDiagArg for PathBuf {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.display().to_string()))
-    }
-}
-
-impl IntoDiagArg for PanicStrategy {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.desc().to_string()))
-    }
-}
-
-impl IntoDiagArg for hir::ConstContext {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(match self {
-            hir::ConstContext::ConstFn => "const_fn",
-            hir::ConstContext::Static(_) => "static",
-            hir::ConstContext::Const { .. } => "const",
-        }))
-    }
-}
-
-impl IntoDiagArg for ast::Expr {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
-    }
-}
-
-impl IntoDiagArg for ast::Path {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))
-    }
-}
-
-impl IntoDiagArg for ast::token::Token {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(pprust::token_to_string(&self))
-    }
-}
-
-impl IntoDiagArg for ast::token::TokenKind {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(pprust::token_kind_to_string(&self))
-    }
-}
-
-impl IntoDiagArg for FloatTy {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.name_str()))
-    }
-}
-
-impl IntoDiagArg for std::ffi::CString {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
-    }
-}
-
-impl IntoDiagArg for rustc_data_structures::small_c_str::SmallCStr {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Owned(self.to_string_lossy().into_owned()))
-    }
-}
-
-impl IntoDiagArg for ast::Visibility {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        let s = pprust::vis_to_string(&self);
-        let s = s.trim_end().to_string();
-        DiagArgValue::Str(Cow::Owned(s))
-    }
-}
-
-impl IntoDiagArg for rustc_lint_defs::Level {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.to_cmd_flag()))
-    }
-}
-
-impl<Id> IntoDiagArg for hir::def::Res<Id> {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.descr()))
-    }
-}
-
 impl IntoDiagArg for DiagLocation {
     fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
         DiagArgValue::Str(Cow::from(self.to_string()))
     }
 }
 
-impl IntoDiagArg for Backtrace {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
-impl IntoDiagArg for Level {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::from(self.to_string()))
-    }
-}
-
-impl IntoDiagArg for ClosureKind {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(self.as_str().into())
-    }
-}
-
-impl IntoDiagArg for hir::def::Namespace {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(Cow::Borrowed(self.descr()))
-    }
-}
-
-impl IntoDiagArg for ExprPrecedence {
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Number(self as i32)
-    }
-}
-
-impl IntoDiagArg for MirDialect {
-    fn into_diag_arg(self, _path: &mut Option<PathBuf>) -> DiagArgValue {
-        let arg = match self {
-            MirDialect::Analysis => "analysis",
-            MirDialect::Built => "built",
-            MirDialect::Runtime => "runtime",
-        };
-        DiagArgValue::Str(Cow::Borrowed(arg))
-    }
-}
-
-impl IntoDiagArg for MirPhase {
-    fn into_diag_arg(self, _path: &mut Option<PathBuf>) -> DiagArgValue {
-        let arg = match self {
-            MirPhase::Initial => "initial",
-            MirPhase::PostCleanup => "post-cleanup",
-            MirPhase::Optimized => "optimized",
-        };
-        DiagArgValue::Str(Cow::Borrowed(arg))
-    }
-}
-
 #[derive(Clone)]
 pub struct DiagSymbolList<S = Symbol>(Vec<S>);
 
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 2534cddf105..0a2bfee8b29 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -41,12 +41,11 @@ use std::{fmt, panic};
 use Level::*;
 pub use codes::*;
 pub use diagnostic::{
-    BugAbort, Diag, DiagArg, DiagArgMap, DiagArgName, DiagArgValue, DiagInner, DiagStyledString,
-    Diagnostic, EmissionGuarantee, FatalAbort, IntoDiagArg, LintDiagnostic, StringPart, Subdiag,
-    Subdiagnostic,
+    BugAbort, Diag, DiagArgMap, DiagInner, DiagStyledString, Diagnostic, EmissionGuarantee,
+    FatalAbort, LintDiagnostic, StringPart, Subdiag, Subdiagnostic,
 };
 pub use diagnostic_impls::{
-    DiagArgFromDisplay, DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,
+    DiagSymbolList, ElidedLifetimeInPathSubdiag, ExpectedLifetimeParameter,
     IndicateAnonymousLifetime, SingleLabelManySpans,
 };
 pub use emitter::ColorConfig;
@@ -56,8 +55,9 @@ use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::{DynSend, Lock};
 pub use rustc_error_messages::{
-    DiagMessage, FluentBundle, LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel,
-    SubdiagMessage, fallback_fluent_bundle, fluent_bundle,
+    DiagArg, DiagArgFromDisplay, DiagArgName, DiagArgValue, DiagMessage, FluentBundle, IntoDiagArg,
+    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, SubdiagMessage,
+    fallback_fluent_bundle, fluent_bundle, into_diag_arg_using_display,
 };
 use rustc_hashes::Hash128;
 use rustc_hir::HirId;
@@ -1999,6 +1999,12 @@ impl Level {
     }
 }
 
+impl IntoDiagArg for Level {
+    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
+        DiagArgValue::Str(Cow::from(self.to_string()))
+    }
+}
+
 // FIXME(eddyb) this doesn't belong here AFAICT, should be moved to callsite.
 pub fn elided_lifetime_in_path_suggestion(
     source_map: &SourceMap,