Auto merge of #120576 - nnethercote:merge-Diagnostic-DiagnosticBuilder, r=davidtwco

Overhaul `Diagnostic` and `DiagnosticBuilder`

Implements the first part of https://github.com/rust-lang/compiler-team/issues/722, which moves functionality and use away from `Diagnostic`, onto `DiagnosticBuilder`.

Likely follow-ups:
- Move things around, because this PR was written to minimize diff size, so some things end up in sub-optimal places. E.g. `DiagnosticBuilder` has impls in both `diagnostic.rs` and `diagnostic_builder.rs`.
- Rename `Diagnostic` as `DiagInner` and `DiagnosticBuilder` as `Diag`.

r? `@davidtwco`

7 files changed, 32 insertions, 28 deletions

diff --git a/compiler/rustc_hir_analysis/src/astconv/errors.rs b/compiler/rustc_hir_analysis/src/astconv/errors.rs
index ad34c31ef8f..214d9602968 100644
--- a/compiler/rustc_hir_analysis/src/astconv/errors.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/errors.rs
@@ -9,7 +9,7 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{
-    codes::*, pluralize, struct_span_code_err, Applicability, Diagnostic, ErrorGuaranteed,
+    codes::*, pluralize, struct_span_code_err, Applicability, DiagnosticBuilder, ErrorGuaranteed,
 };
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -371,7 +371,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     // FIXME(fmease): Heavily adapted from `rustc_hir_typeck::method::suggest`. Deduplicate.
     fn note_ambiguous_inherent_assoc_type(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         candidates: Vec<DefId>,
         span: Span,
     ) {
@@ -429,7 +429,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let tcx = self.tcx();
 
         let adt_did = self_ty.ty_adt_def().map(|def| def.did());
-        let add_def_label = |err: &mut Diagnostic| {
+        let add_def_label = |err: &mut DiagnosticBuilder<'_>| {
             if let Some(did) = adt_did {
                 err.span_label(
                     tcx.def_span(did),
diff --git a/compiler/rustc_hir_analysis/src/astconv/generics.rs b/compiler/rustc_hir_analysis/src/astconv/generics.rs
index 614e5f9d32b..b20326ae5e1 100644
--- a/compiler/rustc_hir_analysis/src/astconv/generics.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/generics.rs
@@ -6,7 +6,7 @@ use crate::astconv::{
 use crate::structured_errors::{GenericArgsInfo, StructuredDiagnostic, WrongNumberOfGenericArgs};
 use rustc_ast::ast::ParamKindOrd;
 use rustc_errors::{
-    codes::*, struct_span_code_err, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan,
+    codes::*, struct_span_code_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
 };
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -47,7 +47,7 @@ fn generic_arg_mismatch_err(
         }
     }
 
-    let add_braces_suggestion = |arg: &GenericArg<'_>, err: &mut Diagnostic| {
+    let add_braces_suggestion = |arg: &GenericArg<'_>, err: &mut DiagnosticBuilder<'_>| {
         let suggestions = vec![
             (arg.span().shrink_to_lo(), String::from("{ ")),
             (arg.span().shrink_to_hi(), String::from(" }")),
diff --git a/compiler/rustc_hir_analysis/src/astconv/lint.rs b/compiler/rustc_hir_analysis/src/astconv/lint.rs
index cee7c84adb2..cee29b152e8 100644
--- a/compiler/rustc_hir_analysis/src/astconv/lint.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/lint.rs
@@ -1,5 +1,5 @@
 use rustc_ast::TraitObjectSyntax;
-use rustc_errors::{codes::*, Diagnostic, StashKey};
+use rustc_errors::{codes::*, DiagnosticBuilder, EmissionGuarantee, StashKey};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_lint_defs::{builtin::BARE_TRAIT_OBJECTS, Applicability};
@@ -10,10 +10,10 @@ use super::AstConv;
 
 impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     /// Make sure that we are in the condition to suggest the blanket implementation.
-    pub(super) fn maybe_lint_blanket_trait_impl(
+    pub(super) fn maybe_lint_blanket_trait_impl<G: EmissionGuarantee>(
         &self,
         self_ty: &hir::Ty<'_>,
-        diag: &mut Diagnostic,
+        diag: &mut DiagnosticBuilder<'_, G>,
     ) {
         let tcx = self.tcx();
         let parent_id = tcx.hir().get_parent_item(self_ty.hir_id).def_id;
@@ -75,7 +75,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     }
 
     /// Make sure that we are in the condition to suggest `impl Trait`.
-    fn maybe_lint_impl_trait(&self, self_ty: &hir::Ty<'_>, diag: &mut Diagnostic) -> bool {
+    fn maybe_lint_impl_trait(
+        &self,
+        self_ty: &hir::Ty<'_>,
+        diag: &mut DiagnosticBuilder<'_>,
+    ) -> bool {
         let tcx = self.tcx();
         let parent_id = tcx.hir().get_parent_item(self_ty.hir_id).def_id;
         let (sig, generics, owner) = match tcx.hir_node_by_def_id(parent_id) {
diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index 296b63a8292..502e83db654 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -18,8 +18,8 @@ use crate::require_c_abi_if_c_variadic;
 use rustc_ast::TraitObjectSyntax;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_errors::{
-    codes::*, struct_span_code_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
-    FatalError, MultiSpan,
+    codes::*, struct_span_code_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, FatalError,
+    MultiSpan,
 };
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
@@ -1724,7 +1724,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     pub fn prohibit_generics<'a>(
         &self,
         segments: impl Iterator<Item = &'a hir::PathSegment<'a>> + Clone,
-        extend: impl Fn(&mut Diagnostic),
+        extend: impl Fn(&mut DiagnosticBuilder<'_>),
     ) -> bool {
         let args = segments.clone().flat_map(|segment| segment.args().args);
 
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index c3948b1b6bd..b3700013f9c 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -1248,7 +1248,7 @@ fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 fn detect_discriminant_duplicate<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) {
     // Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate.
     // Here `idx` refers to the order of which the discriminant appears, and its index in `vs`
-    let report = |dis: Discr<'tcx>, idx, err: &mut Diagnostic| {
+    let report = |dis: Discr<'tcx>, idx, err: &mut DiagnosticBuilder<'_>| {
         let var = adt.variant(idx); // HIR for the duplicate discriminant
         let (span, display_discr) = match var.discr {
             ty::VariantDiscr::Explicit(discr_def_id) => {
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index b9052672a26..36a92a4cf7c 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -78,7 +78,7 @@ use std::num::NonZero;
 
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_errors::ErrorGuaranteed;
-use rustc_errors::{pluralize, struct_span_code_err, Diagnostic, DiagnosticBuilder};
+use rustc_errors::{pluralize, struct_span_code_err, DiagnosticBuilder};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::Visitor;
 use rustc_index::bit_set::BitSet;
diff --git a/compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs b/compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs
index f9d57d402b1..8e0c2ea5ca7 100644
--- a/compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs
+++ b/compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs
@@ -1,5 +1,5 @@
 use crate::structured_errors::StructuredDiagnostic;
-use rustc_errors::{codes::*, pluralize, Applicability, Diagnostic, DiagnosticBuilder, MultiSpan};
+use rustc_errors::{codes::*, pluralize, Applicability, DiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
 use rustc_session::Session;
@@ -525,7 +525,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     }
 
     /// Builds the `expected 1 type argument / supplied 2 type arguments` message.
-    fn notify(&self, err: &mut Diagnostic) {
+    fn notify(&self, err: &mut DiagnosticBuilder<'_>) {
         let (quantifier, bound) = self.get_quantifier_and_bound();
         let provided_args = self.num_provided_args();
 
@@ -577,7 +577,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         }
     }
 
-    fn suggest(&self, err: &mut Diagnostic) {
+    fn suggest(&self, err: &mut DiagnosticBuilder<'_>) {
         debug!(
             "suggest(self.provided {:?}, self.gen_args.span(): {:?})",
             self.num_provided_args(),
@@ -605,7 +605,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     /// ```text
     /// type Map = HashMap<String>;
     /// ```
-    fn suggest_adding_args(&self, err: &mut Diagnostic) {
+    fn suggest_adding_args(&self, err: &mut DiagnosticBuilder<'_>) {
         if self.gen_args.parenthesized != hir::GenericArgsParentheses::No {
             return;
         }
@@ -624,7 +624,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         }
     }
 
-    fn suggest_adding_lifetime_args(&self, err: &mut Diagnostic) {
+    fn suggest_adding_lifetime_args(&self, err: &mut DiagnosticBuilder<'_>) {
         debug!("suggest_adding_lifetime_args(path_segment: {:?})", self.path_segment);
         let num_missing_args = self.num_missing_lifetime_args();
         let num_params_to_take = num_missing_args;
@@ -678,7 +678,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         }
     }
 
-    fn suggest_adding_type_and_const_args(&self, err: &mut Diagnostic) {
+    fn suggest_adding_type_and_const_args(&self, err: &mut DiagnosticBuilder<'_>) {
         let num_missing_args = self.num_missing_type_or_const_args();
         let msg = format!("add missing {} argument{}", self.kind(), pluralize!(num_missing_args));
 
@@ -738,7 +738,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     /// ```compile_fail
     /// Into::into::<Option<_>>(42) // suggests considering `Into::<Option<_>>::into(42)`
     /// ```
-    fn suggest_moving_args_from_assoc_fn_to_trait(&self, err: &mut Diagnostic) {
+    fn suggest_moving_args_from_assoc_fn_to_trait(&self, err: &mut DiagnosticBuilder<'_>) {
         let trait_ = match self.tcx.trait_of_item(self.def_id) {
             Some(def_id) => def_id,
             None => return,
@@ -794,7 +794,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
 
     fn suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         qpath: &'tcx hir::QPath<'tcx>,
         msg: String,
         num_assoc_fn_excess_args: usize,
@@ -827,7 +827,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
 
     fn suggest_moving_args_from_assoc_fn_to_trait_for_method_call(
         &self,
-        err: &mut Diagnostic,
+        err: &mut DiagnosticBuilder<'_>,
         trait_def_id: DefId,
         expr: &'tcx hir::Expr<'tcx>,
         msg: String,
@@ -881,7 +881,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     /// ```text
     /// type Map = HashMap<String, String, String, String>;
     /// ```
-    fn suggest_removing_args_or_generics(&self, err: &mut Diagnostic) {
+    fn suggest_removing_args_or_generics(&self, err: &mut DiagnosticBuilder<'_>) {
         let num_provided_lt_args = self.num_provided_lifetime_args();
         let num_provided_type_const_args = self.num_provided_type_or_const_args();
         let unbound_types = self.get_unbound_associated_types();
@@ -899,7 +899,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         let provided_args_matches_unbound_traits =
             unbound_types.len() == num_redundant_type_or_const_args;
 
-        let remove_lifetime_args = |err: &mut Diagnostic| {
+        let remove_lifetime_args = |err: &mut DiagnosticBuilder<'_>| {
             let mut lt_arg_spans = Vec::new();
             let mut found_redundant = false;
             for arg in self.gen_args.args {
@@ -940,7 +940,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
             );
         };
 
-        let remove_type_or_const_args = |err: &mut Diagnostic| {
+        let remove_type_or_const_args = |err: &mut DiagnosticBuilder<'_>| {
             let mut gen_arg_spans = Vec::new();
             let mut found_redundant = false;
             for arg in self.gen_args.args {
@@ -1037,7 +1037,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     }
 
     /// Builds the `type defined here` message.
-    fn show_definition(&self, err: &mut Diagnostic) {
+    fn show_definition(&self, err: &mut DiagnosticBuilder<'_>) {
         let mut spans: MultiSpan = if let Some(def_span) = self.tcx.def_ident_span(self.def_id) {
             if self.tcx.sess.source_map().is_span_accessible(def_span) {
                 def_span.into()
@@ -1088,7 +1088,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
     }
 
     /// Add note if `impl Trait` is explicitly specified.
-    fn note_synth_provided(&self, err: &mut Diagnostic) {
+    fn note_synth_provided(&self, err: &mut DiagnosticBuilder<'_>) {
         if !self.is_synth_provided() {
             return;
         }