Split hir_typeck_never_type_fallback_flowing_into_unsafe into 5 slugs

compiler/rustc_hir_typeck/messages.ftl

@@ -99,15 +99,15 @@ hir_typeck_lossy_provenance_ptr2int =
 
 hir_typeck_missing_parentheses_in_range = can't call method `{$method_name}` on type `{$ty_str}`
 
-hir_typeck_never_type_fallback_flowing_into_unsafe =
-    never type fallback affects this {$reason ->
-    [call] call to an `unsafe` function
-    [union_field] union access
-    [deref] raw pointer dereference
-    [path] `unsafe` function
-    [method] call to an `unsafe` method
-    *[other] THIS SHOULD NOT BE REACHABLE
-    }
+hir_typeck_never_type_fallback_flowing_into_unsafe_call = never type fallback affects this call to an `unsafe` function
+    .help = specify the type explicitly
+hir_typeck_never_type_fallback_flowing_into_unsafe_deref = never type fallback affects this raw pointer dereference
+    .help = specify the type explicitly
+hir_typeck_never_type_fallback_flowing_into_unsafe_method = never type fallback affects this call to an `unsafe` method
+    .help = specify the type explicitly
+hir_typeck_never_type_fallback_flowing_into_unsafe_path = never type fallback affects this `unsafe` function
+    .help = specify the type explicitly
+hir_typeck_never_type_fallback_flowing_into_unsafe_union_field = never type fallback affects this union access
     .help = specify the type explicitly
 
 hir_typeck_no_associated_item = no {$item_kind} named `{$item_name}` found for {$ty_prefix} `{$ty_str}`{$trait_missing_method ->

compiler/rustc_hir_typeck/src/errors.rs

@@ -1,7 +1,7 @@
 //! Errors emitted by `rustc_hir_typeck`.
 use std::borrow::Cow;
 
-use crate::{fallback::UnsafeUseReason, fluent_generated as fluent};
+use crate::fluent_generated as fluent;
 use rustc_errors::{
     codes::*, Applicability, Diag, DiagArgValue, EmissionGuarantee, IntoDiagArg, MultiSpan,
     SubdiagMessageOp, Subdiagnostic,
@@ -165,10 +165,22 @@ pub struct MissingParenthesesInRange {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(hir_typeck_never_type_fallback_flowing_into_unsafe)]
-#[help]
-pub struct NeverTypeFallbackFlowingIntoUnsafe {
-    pub reason: UnsafeUseReason,
+pub enum NeverTypeFallbackFlowingIntoUnsafe {
+    #[help]
+    #[diag(hir_typeck_never_type_fallback_flowing_into_unsafe_call)]
+    Call,
+    #[help]
+    #[diag(hir_typeck_never_type_fallback_flowing_into_unsafe_method)]
+    Method,
+    #[help]
+    #[diag(hir_typeck_never_type_fallback_flowing_into_unsafe_path)]
+    Path,
+    #[help]
+    #[diag(hir_typeck_never_type_fallback_flowing_into_unsafe_union_field)]
+    UnionField,
+    #[help]
+    #[diag(hir_typeck_never_type_fallback_flowing_into_unsafe_deref)]
+    Deref,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_hir_typeck/src/fallback.rs

@@ -1,11 +1,10 @@
-use std::{borrow::Cow, cell::OnceCell};
+use std::cell::OnceCell;
 
 use crate::{errors, FnCtxt, TypeckRootCtxt};
 use rustc_data_structures::{
     graph::{self, iterate::DepthFirstSearch, vec_graph::VecGraph},
     unord::{UnordBag, UnordMap, UnordSet},
 };
-use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir as hir;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::HirId;
@@ -380,7 +379,23 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
                         lint::builtin::NEVER_TYPE_FALLBACK_FLOWING_INTO_UNSAFE,
                         hir_id,
                         span,
-                        errors::NeverTypeFallbackFlowingIntoUnsafe { reason },
+                        match reason {
+                            UnsafeUseReason::Call => {
+                                errors::NeverTypeFallbackFlowingIntoUnsafe::Call
+                            }
+                            UnsafeUseReason::Method => {
+                                errors::NeverTypeFallbackFlowingIntoUnsafe::Method
+                            }
+                            UnsafeUseReason::Path => {
+                                errors::NeverTypeFallbackFlowingIntoUnsafe::Path
+                            }
+                            UnsafeUseReason::UnionField => {
+                                errors::NeverTypeFallbackFlowingIntoUnsafe::UnionField
+                            }
+                            UnsafeUseReason::Deref => {
+                                errors::NeverTypeFallbackFlowingIntoUnsafe::Deref
+                            }
+                        },
                     );
                 }
 
@@ -503,19 +518,6 @@ pub(crate) enum UnsafeUseReason {
     Deref,
 }
 
-impl IntoDiagArg for UnsafeUseReason {
-    fn into_diag_arg(self) -> DiagArgValue {
-        let s = match self {
-            UnsafeUseReason::Call => "call",
-            UnsafeUseReason::Method => "method",
-            UnsafeUseReason::Path => "path",
-            UnsafeUseReason::UnionField => "union_field",
-            UnsafeUseReason::Deref => "deref",
-        };
-        DiagArgValue::Str(Cow::Borrowed(s))
-    }
-}
-
 /// Finds all type variables which are passed to an `unsafe` operation.
 ///
 /// For example, for this function `f`: