Migrate pattern bindings with variant name lint

Author: lzcunt

compiler/rustc_error_messages/locales/en-US/mir_build.ftl

@@ -233,3 +233,7 @@ mir_build_trailing_irrefutable_let_patterns = trailing irrefutable {$count ->
         [one] it
         *[other] them
     } into the body
+
+mir_build_bindings_with_variant_name =
+    pattern binding `{$ident}` is named the same as one of the variants of the type `{$ty_path}`
+    .suggestion = to match on the variant, qualify the path

compiler/rustc_mir_build/src/errors.rs

@@ -3,7 +3,7 @@ use rustc_errors::{error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed
 use rustc_macros::{LintDiagnostic, SessionDiagnostic, SessionSubdiagnostic};
 use rustc_middle::ty::{self, Ty};
 use rustc_session::{parse::ParseSess, SessionDiagnostic};
-use rustc_span::Span;
+use rustc_span::{symbol::Ident, Span};
 
 #[derive(LintDiagnostic)]
 #[diag(mir_build::unconditional_recursion)]
@@ -513,3 +513,12 @@ pub struct LeadingIrrefutableLetPatterns {
 pub struct TrailingIrrefutableLetPatterns {
     pub count: usize,
 }
+
+#[derive(LintDiagnostic)]
+#[diag(mir_build::bindings_with_variant_name, code = "E0170")]
+pub struct BindingsWithVariantName {
+    #[suggestion(code = "{ty_path}::{ident}", applicability = "machine-applicable")]
+    pub suggestion: Option<Span>,
+    pub ty_path: String,
+    pub ident: Ident,
+}

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -9,8 +9,8 @@ use crate::errors::*;
 use rustc_arena::TypedArena;
 use rustc_ast::Mutability;
 use rustc_errors::{
-    error_code, pluralize, struct_span_err, Applicability, DelayDm, Diagnostic, DiagnosticBuilder,
-    ErrorGuaranteed, MultiSpan,
+    pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
+    MultiSpan,
 };
 use rustc_hir as hir;
 use rustc_hir::def::*;
@@ -547,32 +547,20 @@ fn check_for_bindings_named_same_as_variants(
             })
         {
             let variant_count = edef.variants().len();
-            cx.tcx.struct_span_lint_hir(
+            let ty_path = cx.tcx.def_path_str(edef.did());
+            cx.tcx.emit_spanned_lint(
                 BINDINGS_WITH_VARIANT_NAME,
                 p.hir_id,
                 p.span,
-                DelayDm(|| format!(
-                    "pattern binding `{}` is named the same as one \
-                        of the variants of the type `{}`",
-                    ident, cx.tcx.def_path_str(edef.did())
-                )),
-                |lint| {
-                    let ty_path = cx.tcx.def_path_str(edef.did());
-                    lint.code(error_code!(E0170));
-
+                BindingsWithVariantName {
                     // If this is an irrefutable pattern, and there's > 1 variant,
                     // then we can't actually match on this. Applying the below
                     // suggestion would produce code that breaks on `check_irrefutable`.
-                    if rf == Refutable || variant_count == 1 {
-                        lint.span_suggestion(
-                            p.span,
-                            "to match on the variant, qualify the path",
-                            format!("{}::{}", ty_path, ident),
-                            Applicability::MachineApplicable,
-                        );
-                    }
-
-                    lint
+                    suggestion: if rf == Refutable || variant_count == 1 {
+                        Some(p.span)
+                    } else { None },
+                    ty_path,
+                    ident,
                 },
             )
         }