Migrate (most of) report_and_explain_type_error

5 files changed, 397 insertions, 229 deletions

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 61338ac613a..9bdce1ee071 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -768,7 +768,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let (provided_ty, provided_span) = provided_arg_tys[*provided_idx];
             let trace =
                 mk_trace(provided_span, formal_and_expected_inputs[*expected_idx], provided_ty);
-            if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308(_)) {
+            if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308) {
                 self.err_ctxt().report_and_explain_type_error(trace, *e).emit();
                 return true;
             }
diff --git a/compiler/rustc_infer/messages.ftl b/compiler/rustc_infer/messages.ftl
index 0f33660e50c..163992658e1 100644
--- a/compiler/rustc_infer/messages.ftl
+++ b/compiler/rustc_infer/messages.ftl
@@ -370,3 +370,25 @@ infer_stp_wrap_one = try wrapping the pattern in `{$variant}`
 infer_stp_wrap_many = try wrapping the pattern in a variant of `{$path}`
 
 infer_tuple_trailing_comma = use a trailing comma to create a tuple with one element
+
+infer_oc_method_compat = method not compatible with trait
+infer_oc_type_compat = type not compatible with trait
+infer_oc_const_compat = const not compatible with trait
+infer_oc_try_compat = `?` operator has incompatible types
+infer_oc_match_compat = `match` arms have incompatible types
+infer_oc_if_else_different = `if` and `else` have incompatible types
+infer_oc_no_else = `if` may be missing an `else` clause
+infer_oc_no_diverge = `else` clause of `let...else` does not diverge
+infer_oc_fn_main_correct_type = `main` function has wrong type
+infer_oc_fn_start_correct_type = `#[start]` function has wrong type
+infer_oc_intristic_correct_type = intrinsic has wrong type
+infer_oc_method_correct_type = mismatched `self` parameter type
+infer_oc_closure_selfref = closure/generator type that references itself
+infer_oc_cant_coerce = cannot coerce intrinsics to function pointers
+infer_oc_generic = mismatched types
+
+infer_meant_byte_literal = if you meant to write a byte literal, prefix with `b`
+infer_meant_char_literal = if you meant to write a `char` literal, use single quotes
+infer_meant_str_literal = if you meant to write a `str` literal, use double quotes
+infer_consider_specifying_length = consider specifying the actual array length
+infer_try_cannot_convert = `?` operator cannot convert from `{$found}` to `{$expected}`
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 6432ae7d3f8..f3bed305f84 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -184,18 +184,6 @@ pub enum SourceKindMultiSuggestion<'a> {
     },
 }
 
-#[derive(Subdiagnostic)]
-#[suggestion(
-    infer_suggest_add_let_for_letchains,
-    style = "verbose",
-    applicability = "machine-applicable",
-    code = "let "
-)]
-pub(crate) struct SuggAddLetForLetChains {
-    #[primary_span]
-    pub span: Span,
-}
-
 impl<'a> SourceKindMultiSuggestion<'a> {
     pub fn new_fully_qualified(
         span: Span,
@@ -1373,17 +1361,172 @@ impl AddToDiagnostic for SuggestTuplePatternMany {
 }
 
 #[derive(Subdiagnostic)]
-pub enum TupleTrailingCommaSuggestion {
+pub enum Error0308Subdiags {
+    #[suggestion(
+        infer_meant_byte_literal,
+        code = "b'{code}'",
+        applicability = "machine-applicable"
+    )]
+    MeantByteLiteral {
+        #[primary_span]
+        span: Span,
+        code: String,
+    },
+    #[suggestion(
+        infer_meant_char_literal,
+        code = "'{code}'",
+        applicability = "machine-applicable"
+    )]
+    MeantCharLiteral {
+        #[primary_span]
+        span: Span,
+        code: String,
+    },
+    #[suggestion(
+        infer_meant_str_literal,
+        code = "\"{code}\"",
+        applicability = "machine-applicable"
+    )]
+    MeantStrLiteral {
+        #[primary_span]
+        span: Span,
+        code: String,
+    },
+    #[suggestion(
+        infer_consider_specifying_length,
+        code = "{length}",
+        applicability = "maybe-incorrect"
+    )]
+    ConsiderSpecifyingLength {
+        #[primary_span]
+        span: Span,
+        length: u64,
+    },
+    #[note(infer_try_cannot_convert)]
+    TryCannotConvert { found: String, expected: String },
     #[suggestion(infer_tuple_trailing_comma, code = ",", applicability = "machine-applicable")]
-    OnlyComma {
+    TupleOnlyComma {
         #[primary_span]
         span: Span,
     },
     #[multipart_suggestion(infer_tuple_trailing_comma, applicability = "machine-applicable")]
-    AlsoParentheses {
+    TupleAlsoParentheses {
         #[suggestion_part(code = "(")]
         span_low: Span,
         #[suggestion_part(code = ",)")]
         span_high: Span,
     },
+    #[suggestion(
+        infer_suggest_add_let_for_letchains,
+        style = "verbose",
+        applicability = "machine-applicable",
+        code = "let "
+    )]
+    AddLetForLetChains {
+        #[primary_span]
+        span: Span,
+    },
+}
+
+#[derive(Diagnostic)]
+pub enum FailureCodeDiagnostics {
+    #[diag(infer_oc_method_compat, code = "E0308")]
+    MethodCompat {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_type_compat, code = "E0308")]
+    TypeCompat {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_const_compat, code = "E0308")]
+    ConstCompat {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_try_compat, code = "E0308")]
+    TryCompat {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_match_compat, code = "E0308")]
+    MatchCompat {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_if_else_different, code = "E0308")]
+    IfElseDifferent {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_no_else, code = "E0317")]
+    NoElse {
+        #[primary_span]
+        span: Span,
+    },
+    #[diag(infer_oc_no_diverge, code = "E0308")]
+    NoDiverge {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_fn_main_correct_type, code = "E0580")]
+    FnMainCorrectType {
+        #[primary_span]
+        span: Span,
+    },
+    #[diag(infer_oc_fn_start_correct_type, code = "E0308")]
+    FnStartCorrectType {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_intristic_correct_type, code = "E0308")]
+    IntristicCorrectType {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_method_correct_type, code = "E0308")]
+    MethodCorrectType {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_closure_selfref, code = "E0644")]
+    ClosureSelfref {
+        #[primary_span]
+        span: Span,
+    },
+    #[diag(infer_oc_cant_coerce, code = "E0308")]
+    CantCoerce {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
+    #[diag(infer_oc_generic, code = "E0308")]
+    Generic {
+        #[primary_span]
+        span: Span,
+        #[subdiagnostic]
+        subdiags: Vec<Error0308Subdiags>,
+    },
 }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index de9aa45c315..4b7f4fe1aaa 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -49,8 +49,7 @@ use super::lexical_region_resolve::RegionResolutionError;
 use super::region_constraints::GenericKind;
 use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
 
-use crate::errors;
-use crate::errors::TupleTrailingCommaSuggestion;
+use crate::errors::{self, Error0308Subdiags, FailureCodeDiagnostics};
 use crate::infer;
 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
 use crate::infer::ExpectedFound;
@@ -1899,225 +1898,196 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         debug!(?diag);
     }
 
-    pub fn report_and_explain_type_error(
+    pub fn type_error_additional_suggestions(
         &self,
-        trace: TypeTrace<'tcx>,
+        trace: &TypeTrace<'tcx>,
         terr: TypeError<'tcx>,
-    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    ) -> Vec<Error0308Subdiags> {
         use crate::traits::ObligationCauseCode::MatchExpressionArm;
-
-        debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
-
+        fn escape_literal(s: &str) -> String {
+            let mut escaped = String::with_capacity(s.len());
+            let mut chrs = s.chars().peekable();
+            while let Some(first) = chrs.next() {
+                match (first, chrs.peek()) {
+                    ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
+                        escaped.push('\\');
+                        escaped.push(delim);
+                        chrs.next();
+                    }
+                    ('"' | '\'', _) => {
+                        escaped.push('\\');
+                        escaped.push(first)
+                    }
+                    (c, _) => escaped.push(c),
+                };
+            }
+            escaped
+        }
+        let mut suggestions = Vec::new();
         let span = trace.cause.span();
-        let failure_code = trace.cause.as_failure_code(terr);
-        let mut diag = match failure_code {
-            FailureCode::Error0317(failure_str) => {
-                struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str)
-            }
-            FailureCode::Error0580(failure_str) => {
-                struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str)
-            }
-            FailureCode::Error0308(failure_str) => {
-                fn escape_literal(s: &str) -> String {
-                    let mut escaped = String::with_capacity(s.len());
-                    let mut chrs = s.chars().peekable();
-                    while let Some(first) = chrs.next() {
-                        match (first, chrs.peek()) {
-                            ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
-                                escaped.push('\\');
-                                escaped.push(delim);
-                                chrs.next();
-                            }
-                            ('"' | '\'', _) => {
-                                escaped.push('\\');
-                                escaped.push(first)
-                            }
-                            (c, _) => escaped.push(c),
-                        };
+        if let Some((expected, found)) = trace.values.ty() {
+            match (expected.kind(), found.kind()) {
+                (ty::Tuple(_), ty::Tuple(_)) => {}
+                // If a tuple of length one was expected and the found expression has
+                // parentheses around it, perhaps the user meant to write `(expr,)` to
+                // build a tuple (issue #86100)
+                (ty::Tuple(fields), _) => {
+                    suggestions.extend(self.tuple_wrap_err_subdiag( span, found, fields))
+                }
+                // If a byte was expected and the found expression is a char literal
+                // containing a single ASCII character, perhaps the user meant to write `b'c'` to
+                // specify a byte literal
+                (ty::Uint(ty::UintTy::U8), ty::Char) => {
+                    if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
+                        && let Some(code) = code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
+                        && !code.starts_with("\\u") // forbid all Unicode escapes
+                        && code.chars().next().map_or(false, |c| c.is_ascii()) // forbids literal Unicode characters beyond ASCII
+                    {
+                        suggestions.push(Error0308Subdiags::MeantByteLiteral { span, code: escape_literal(code) })
                     }
-                    escaped
                 }
-                let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str);
-                let values = self.resolve_vars_if_possible(trace.values);
-                if let Some((expected, found)) = values.ty() {
-                    match (expected.kind(), found.kind()) {
-                        (ty::Tuple(_), ty::Tuple(_)) => {}
-                        // If a tuple of length one was expected and the found expression has
-                        // parentheses around it, perhaps the user meant to write `(expr,)` to
-                        // build a tuple (issue #86100)
-                        (ty::Tuple(fields), _) => {
-                            self.emit_tuple_wrap_err(&mut err, span, found, fields)
-                        }
-                        // If a byte was expected and the found expression is a char literal
-                        // containing a single ASCII character, perhaps the user meant to write `b'c'` to
-                        // specify a byte literal
-                        (ty::Uint(ty::UintTy::U8), ty::Char) => {
-                            if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
-                                && let Some(code) = code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
-                                && !code.starts_with("\\u") // forbid all Unicode escapes
-                                && code.chars().next().map_or(false, |c| c.is_ascii()) // forbids literal Unicode characters beyond ASCII
-                            {
-                                err.span_suggestion(
-                                    span,
-                                    "if you meant to write a byte literal, prefix with `b`",
-                                    format!("b'{}'", escape_literal(code)),
-                                    Applicability::MachineApplicable,
-                                );
-                            }
-                        }
-                        // If a character was expected and the found expression is a string literal
-                        // containing a single character, perhaps the user meant to write `'c'` to
-                        // specify a character literal (issue #92479)
-                        (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
-                            if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
-                                && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
-                                && code.chars().count() == 1
-                            {
-                                err.span_suggestion(
-                                    span,
-                                    "if you meant to write a `char` literal, use single quotes",
-                                    format!("'{}'", escape_literal(code)),
-                                    Applicability::MachineApplicable,
-                                );
-                            }
+                // If a character was expected and the found expression is a string literal
+                // containing a single character, perhaps the user meant to write `'c'` to
+                // specify a character literal (issue #92479)
+                (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
+                    if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
+                        && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
+                        && code.chars().count() == 1
+                    {
+                        suggestions.push(Error0308Subdiags::MeantCharLiteral { span, code: escape_literal(code) })
+                    }
+                }
+                // If a string was expected and the found expression is a character literal,
+                // perhaps the user meant to write `"s"` to specify a string literal.
+                (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
+                    if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
+                        if let Some(code) =
+                            code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
+                        {
+                            suggestions.push(Error0308Subdiags::MeantStrLiteral { span, code: escape_literal(code) })
                         }
-                        // If a string was expected and the found expression is a character literal,
-                        // perhaps the user meant to write `"s"` to specify a string literal.
-                        (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
-                            if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
-                                if let Some(code) =
-                                    code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
-                                {
-                                    err.span_suggestion(
-                                        span,
-                                        "if you meant to write a `str` literal, use double quotes",
-                                        format!("\"{}\"", escape_literal(code)),
-                                        Applicability::MachineApplicable,
-                                    );
-                                }
+                    }
+                }
+                // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
+                // we try to suggest to add the missing `let` for `if let Some(..) = expr`
+                (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
+                    suggestions.extend(self.suggest_let_for_letchains(&trace.cause, span));
+                }
+                (ty::Array(_, _), ty::Array(_, _)) => 'block: {
+                    let hir = self.tcx.hir();
+                    let TypeError::FixedArraySize(sz) = terr else {
+                        break 'block;
+                    };
+                    let tykind = match hir.find_by_def_id(trace.cause.body_id) {
+                        Some(hir::Node::Item(hir::Item {
+                            kind: hir::ItemKind::Fn(_, _, body_id),
+                            ..
+                        })) => {
+                            let body = hir.body(*body_id);
+                            struct LetVisitor<'v> {
+                                span: Span,
+                                result: Option<&'v hir::Ty<'v>>,
                             }
-                        }
-                        // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
-                        // we try to suggest to add the missing `let` for `if let Some(..) = expr`
-                        (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
-                            self.suggest_let_for_letchains(&mut err, &trace.cause, span);
-                        }
-                        (ty::Array(_, _), ty::Array(_, _)) => 'block: {
-                            let hir = self.tcx.hir();
-                            let TypeError::FixedArraySize(sz) = terr else {
-                                break 'block;
-                            };
-                            let tykind = match hir.find_by_def_id(trace.cause.body_id) {
-                                Some(hir::Node::Item(hir::Item {
-                                    kind: hir::ItemKind::Fn(_, _, body_id),
-                                    ..
-                                })) => {
-                                    let body = hir.body(*body_id);
-                                    struct LetVisitor<'v> {
-                                        span: Span,
-                                        result: Option<&'v hir::Ty<'v>>,
+                            impl<'v> Visitor<'v> for LetVisitor<'v> {
+                                fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
+                                    if self.result.is_some() {
+                                        return;
                                     }
-                                    impl<'v> Visitor<'v> for LetVisitor<'v> {
-                                        fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
-                                            if self.result.is_some() {
-                                                return;
-                                            }
-                                            // Find a local statement where the initializer has
-                                            // the same span as the error and the type is specified.
-                                            if let hir::Stmt {
-                                                kind: hir::StmtKind::Local(hir::Local {
-                                                    init: Some(hir::Expr {
-                                                        span: init_span,
-                                                        ..
-                                                    }),
-                                                    ty: Some(array_ty),
-                                                    ..
-                                                }),
+                                    // Find a local statement where the initializer has
+                                    // the same span as the error and the type is specified.
+                                    if let hir::Stmt {
+                                        kind: hir::StmtKind::Local(hir::Local {
+                                            init: Some(hir::Expr {
+                                                span: init_span,
                                                 ..
-                                            } = s
-                                            && init_span == &self.span {
-                                                self.result = Some(*array_ty);
-                                            }
-                                        }
+                                            }),
+                                            ty: Some(array_ty),
+                                            ..
+                                        }),
+                                        ..
+                                    } = s
+                                    && init_span == &self.span {
+                                        self.result = Some(*array_ty);
                                     }
-                                    let mut visitor = LetVisitor {span, result: None};
-                                    visitor.visit_body(body);
-                                    visitor.result.map(|r| &r.peel_refs().kind)
-                                }
-                                Some(hir::Node::Item(hir::Item {
-                                    kind: hir::ItemKind::Const(ty, _),
-                                    ..
-                                })) => {
-                                    Some(&ty.peel_refs().kind)
                                 }
-                                _ => None
-                            };
-
-                            if let Some(tykind) = tykind
-                                && let hir::TyKind::Array(_, length) = tykind
-                                && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
-                                && let Some(span) = self.tcx.hir().opt_span(*hir_id)
-                            {
-                                err.span_suggestion(
-                                    span,
-                                    "consider specifying the actual array length",
-                                    sz.found,
-                                    Applicability::MaybeIncorrect,
-                                );
                             }
+                            let mut visitor = LetVisitor {span, result: None};
+                            visitor.visit_body(body);
+                            visitor.result.map(|r| &r.peel_refs().kind)
                         }
-                        _ => {}
+                        Some(hir::Node::Item(hir::Item {
+                            kind: hir::ItemKind::Const(ty, _),
+                            ..
+                        })) => {
+                            Some(&ty.peel_refs().kind)
+                        }
+                        _ => None
+                    };
+
+                    if let Some(tykind) = tykind
+                        && let hir::TyKind::Array(_, length) = tykind
+                        && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
+                        && let Some(span) = self.tcx.hir().opt_span(*hir_id)
+                    {
+                        suggestions.push(Error0308Subdiags::ConsiderSpecifyingLength { span, length: sz.found });
                     }
                 }
-                let code = trace.cause.code();
-                if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
+                _ => {}
+            }
+        }
+        let code = trace.cause.code();
+        if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
                     && let hir::MatchSource::TryDesugar = source
                     && let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
                 {
-                    err.note(&format!(
-                        "`?` operator cannot convert from `{}` to `{}`",
-                        found_ty.content(),
-                        expected_ty.content(),
-                    ));
+                    suggestions.push(Error0308Subdiags::TryCannotConvert { found: found_ty.content(), expected: expected_ty.content() });
                 }
-                err
-            }
-            FailureCode::Error0644(failure_str) => {
-                struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str)
-            }
-        };
+        suggestions
+    }
+
+    pub fn report_and_explain_type_error(
+        &self,
+        trace: TypeTrace<'tcx>,
+        terr: TypeError<'tcx>,
+    ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+        debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
+
+        let span = trace.cause.span();
+        let failure_code = trace.cause.as_failure_code_diag(
+            terr,
+            span,
+            self.type_error_additional_suggestions(&trace, terr),
+        );
+        let mut diag = self.tcx.sess.create_err(failure_code);
         self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
         diag
     }
 
-    fn emit_tuple_wrap_err(
+    fn tuple_wrap_err_subdiag(
         &self,
-        err: &mut Diagnostic,
         span: Span,
         found: Ty<'tcx>,
         expected_fields: &List<Ty<'tcx>>,
-    ) {
-        let [expected_tup_elem] = expected_fields[..] else { return };
+    ) -> Option<Error0308Subdiags> {
+        let [expected_tup_elem] = expected_fields[..] else { return None};
 
         if !self.same_type_modulo_infer(expected_tup_elem, found) {
-            return;
+            return None;
         }
 
         let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
-            else { return };
+            else { return None };
 
         let sugg = if code.starts_with('(') && code.ends_with(')') {
             let before_close = span.hi() - BytePos::from_u32(1);
-            TupleTrailingCommaSuggestion::OnlyComma {
-                span: span.with_hi(before_close).shrink_to_hi(),
-            }
+            Error0308Subdiags::TupleOnlyComma { span: span.with_hi(before_close).shrink_to_hi() }
         } else {
-            TupleTrailingCommaSuggestion::AlsoParentheses {
+            Error0308Subdiags::TupleAlsoParentheses {
                 span_low: span.shrink_to_lo(),
                 span_high: span.shrink_to_hi(),
             }
         };
-        err.subdiagnostic(sugg);
+        Some(sugg)
     }
 
     fn values_str(
@@ -2820,14 +2790,21 @@ impl<'tcx> InferCtxt<'tcx> {
 }
 
 pub enum FailureCode {
-    Error0317(&'static str),
-    Error0580(&'static str),
-    Error0308(&'static str),
-    Error0644(&'static str),
+    Error0317,
+    Error0580,
+    Error0308,
+    Error0644,
 }
 
 pub trait ObligationCauseExt<'tcx> {
     fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
+
+    fn as_failure_code_diag(
+        &self,
+        terr: TypeError<'tcx>,
+        span: Span,
+        subdiags: Vec<Error0308Subdiags>,
+    ) -> FailureCodeDiagnostics;
     fn as_requirement_str(&self) -> &'static str;
 }
 
@@ -2836,40 +2813,66 @@ impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
         use self::FailureCode::*;
         use crate::traits::ObligationCauseCode::*;
         match self.code() {
+            IfExpressionWithNoElse => Error0317,
+            MainFunctionType => Error0580,
+            CompareImplItemObligation { .. }
+            | MatchExpressionArm(_)
+            | IfExpression { .. }
+            | LetElse
+            | StartFunctionType
+            | IntrinsicType
+            | MethodReceiver => Error0308,
+
+            // In the case where we have no more specific thing to
+            // say, also take a look at the error code, maybe we can
+            // tailor to that.
+            _ => match terr {
+                TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => Error0644,
+                TypeError::IntrinsicCast => Error0308,
+                _ => Error0308,
+            },
+        }
+    }
+    fn as_failure_code_diag(
+        &self,
+        terr: TypeError<'tcx>,
+        span: Span,
+        subdiags: Vec<Error0308Subdiags>,
+    ) -> FailureCodeDiagnostics {
+        use crate::traits::ObligationCauseCode::*;
+        match self.code() {
             CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
-                Error0308("method not compatible with trait")
+                FailureCodeDiagnostics::MethodCompat { span, subdiags }
             }
             CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
-                Error0308("type not compatible with trait")
+                FailureCodeDiagnostics::TypeCompat { span, subdiags }
             }
             CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
-                Error0308("const not compatible with trait")
-            }
-            MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
-                Error0308(match source {
-                    hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
-                    _ => "`match` arms have incompatible types",
-                })
-            }
-            IfExpression { .. } => Error0308("`if` and `else` have incompatible types"),
-            IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"),
-            LetElse => Error0308("`else` clause of `let...else` does not diverge"),
-            MainFunctionType => Error0580("`main` function has wrong type"),
-            StartFunctionType => Error0308("`#[start]` function has wrong type"),
-            IntrinsicType => Error0308("intrinsic has wrong type"),
-            MethodReceiver => Error0308("mismatched `self` parameter type"),
+                FailureCodeDiagnostics::ConstCompat { span, subdiags }
+            }
+            MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => match source {
+                hir::MatchSource::TryDesugar => {
+                    FailureCodeDiagnostics::TryCompat { span, subdiags }
+                }
+                _ => FailureCodeDiagnostics::MatchCompat { span, subdiags },
+            },
+            IfExpression { .. } => FailureCodeDiagnostics::IfElseDifferent { span, subdiags },
+            IfExpressionWithNoElse => FailureCodeDiagnostics::NoElse { span },
+            LetElse => FailureCodeDiagnostics::NoDiverge { span, subdiags },
+            MainFunctionType => FailureCodeDiagnostics::FnMainCorrectType { span },
+            StartFunctionType => FailureCodeDiagnostics::FnStartCorrectType { span, subdiags },
+            IntrinsicType => FailureCodeDiagnostics::IntristicCorrectType { span, subdiags },
+            MethodReceiver => FailureCodeDiagnostics::MethodCorrectType { span, subdiags },
 
             // In the case where we have no more specific thing to
             // say, also take a look at the error code, maybe we can
             // tailor to that.
             _ => match terr {
                 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
-                    Error0644("closure/generator type that references itself")
-                }
-                TypeError::IntrinsicCast => {
-                    Error0308("cannot coerce intrinsics to function pointers")
+                    FailureCodeDiagnostics::ClosureSelfref { span }
                 }
-                _ => Error0308("mismatched types"),
+                TypeError::IntrinsicCast => FailureCodeDiagnostics::CantCoerce { span, subdiags },
+                _ => FailureCodeDiagnostics::Generic { span, subdiags },
             },
         }
     }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
index e7f5fdaef74..fecfc53c86a 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
@@ -13,10 +13,10 @@ use rustc_span::{sym, BytePos, Span};
 use rustc_target::abi::FieldIdx;
 
 use crate::errors::{
-    ConsiderAddingAwait, DiagArg, FnConsiderCasting, FnItemsAreDistinct, FnUniqTypes,
-    FunctionPointerSuggestion, SuggAddLetForLetChains, SuggestAccessingField,
-    SuggestAsRefWhereAppropriate, SuggestBoxingForReturnImplTrait,
-    SuggestRemoveSemiOrReturnBinding, SuggestTuplePatternMany, SuggestTuplePatternOne,
+    ConsiderAddingAwait, DiagArg, Error0308Subdiags, FnConsiderCasting, FnItemsAreDistinct,
+    FnUniqTypes, FunctionPointerSuggestion, SuggestAccessingField, SuggestAsRefWhereAppropriate,
+    SuggestBoxingForReturnImplTrait, SuggestRemoveSemiOrReturnBinding, SuggestTuplePatternMany,
+    SuggestTuplePatternOne,
 };
 
 use super::TypeErrCtxt;
@@ -482,10 +482,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
     /// and then try to find a assignment in the `cond` part, which span is equal with error span
     pub(super) fn suggest_let_for_letchains(
         &self,
-        err: &mut Diagnostic,
         cause: &ObligationCause<'_>,
         span: Span,
-    ) {
+    ) -> Option<Error0308Subdiags> {
         let hir = self.tcx.hir();
         if let Some(node) = self.tcx.hir().find_by_def_id(cause.body_id) &&
             let hir::Node::Item(hir::Item {
@@ -532,9 +531,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let mut visitor = IfVisitor { err_span: span, found_if: false, result: false };
         visitor.visit_body(&body);
         if visitor.result {
-                err.subdiagnostic(SuggAddLetForLetChains{span: span.shrink_to_lo()});
+                return Some(Error0308Subdiags::AddLetForLetChains{span: span.shrink_to_lo()});
             }
         }
+        None
     }
 }