migrate rustc_hir_analysis to session diagnostic

part two
files list:
rustc_hir_analysis/variance/*
rustc_hir_analysis/missing_cast_for_variadic_arg.rs
rustc_hir_analysis/sized_unsized_cast.rs

compiler/rustc_hir_analysis/locales/en-US.ftl

@@ -155,3 +155,11 @@ hir_analysis_cannot_capture_late_bound_ty_in_anon_const =
 hir_analysis_cannot_capture_late_bound_const_in_anon_const =
     cannot capture late-bound const parameter in a constant
     .label = parameter defined here
+
+hir_analysis_variances_of = {$variances_of}
+
+hir_analysis_pass_to_variadic_function = can't pass `{$ty}` to variadic function
+    .suggestion = cast the value to `{$cast_ty}`
+    .help = cast the value to `{$cast_ty}`
+
+hir_analysis_cast_thin_pointer_to_fat_pointer = cannot cast thin pointer `{$expr_ty}` to fat pointer `{$cast_ty}`

compiler/rustc_hir_analysis/src/errors.rs

@@ -399,3 +399,34 @@ pub(crate) enum CannotCaptureLateBoundInAnonConst {
         def_span: Span,
     },
 }
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_variances_of)]
+pub(crate) struct VariancesOf {
+    #[primary_span]
+    pub span: Span,
+    pub variances_of: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_pass_to_variadic_function, code = "E0617")]
+pub(crate) struct PassToVariadicFunction<'tcx, 'a> {
+    #[primary_span]
+    pub span: Span,
+    pub ty: Ty<'tcx>,
+    pub cast_ty: &'a str,
+    #[suggestion(code = "{replace}", applicability = "machine-applicable")]
+    pub sugg_span: Option<Span>,
+    pub replace: String,
+    #[help]
+    pub help: Option<()>,
+}
+
+#[derive(Diagnostic)]
+#[diag(hir_analysis_cast_thin_pointer_to_fat_pointer, code = "E0607")]
+pub(crate) struct CastThinPointerToFatPointer<'tcx> {
+    #[primary_span]
+    pub span: Span,
+    pub expr_ty: Ty<'tcx>,
+    pub cast_ty: String,
+}

compiler/rustc_hir_analysis/src/structured_errors/missing_cast_for_variadic_arg.rs

@@ -1,5 +1,5 @@
-use crate::structured_errors::StructuredDiagnostic;
-use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
+use crate::{errors, structured_errors::StructuredDiagnostic};
+use rustc_errors::{DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
 use rustc_middle::ty::{Ty, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::Span;
@@ -21,27 +21,26 @@ impl<'tcx> StructuredDiagnostic<'tcx> for MissingCastForVariadicArg<'tcx, '_> {
     }
 
     fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let mut err = self.sess.struct_span_err_with_code(
-            self.span,
-            &format!("can't pass `{}` to variadic function", self.ty),
-            self.code(),
-        );
+        let (sugg_span, replace, help) =
+            if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.span) {
+                (Some(self.span), format!("{} as {}", snippet, self.cast_ty), None)
+            } else {
+                (None, "".to_string(), Some(()))
+            };
+
+        let mut err = self.sess.create_err(errors::PassToVariadicFunction {
+            span: self.span,
+            ty: self.ty,
+            cast_ty: self.cast_ty,
+            help,
+            replace,
+            sugg_span,
+        });
 
         if self.ty.references_error() {
             err.downgrade_to_delayed_bug();
         }
 
-        if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.span) {
-            err.span_suggestion(
-                self.span,
-                &format!("cast the value to `{}`", self.cast_ty),
-                format!("{} as {}", snippet, self.cast_ty),
-                Applicability::MachineApplicable,
-            );
-        } else {
-            err.help(&format!("cast the value to `{}`", self.cast_ty));
-        }
-
         err
     }
 

compiler/rustc_hir_analysis/src/structured_errors/sized_unsized_cast.rs

@@ -1,4 +1,4 @@
-use crate::structured_errors::StructuredDiagnostic;
+use crate::{errors, structured_errors::StructuredDiagnostic};
 use rustc_errors::{DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
 use rustc_middle::ty::{Ty, TypeVisitableExt};
 use rustc_session::Session;
@@ -21,14 +21,11 @@ impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCast<'tcx> {
     }
 
     fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let mut err = self.sess.struct_span_err_with_code(
-            self.span,
-            &format!(
-                "cannot cast thin pointer `{}` to fat pointer `{}`",
-                self.expr_ty, self.cast_ty
-            ),
-            self.code(),
-        );
+        let mut err = self.sess.create_err(errors::CastThinPointerToFatPointer {
+            span: self.span,
+            expr_ty: self.expr_ty,
+            cast_ty: self.cast_ty.to_owned(),
+        });
 
         if self.expr_ty.references_error() {
             err.downgrade_to_delayed_bug();

compiler/rustc_hir_analysis/src/variance/test.rs

@@ -1,14 +1,19 @@
 use rustc_middle::ty::TyCtxt;
 use rustc_span::symbol::sym;
 
+use crate::errors;
+
 pub fn test_variance(tcx: TyCtxt<'_>) {
     // For unit testing: check for a special "rustc_variance"
     // attribute and report an error with various results if found.
     for id in tcx.hir().items() {
         if tcx.has_attr(id.owner_id.to_def_id(), sym::rustc_variance) {
             let variances_of = tcx.variances_of(id.owner_id);
 
-            tcx.sess.struct_span_err(tcx.def_span(id.owner_id), format!("{variances_of:?}")).emit();
+            tcx.sess.emit_err(errors::VariancesOf {
+                span: tcx.def_span(id.owner_id),
+                variances_of: format!("{variances_of:?}"),
+            });
         }
     }
 }