UPDATE - migrate base.rs to new diagnostics infrastructure

compiler/rustc_codegen_ssa/src/base.rs

@@ -5,6 +5,7 @@
     submit_post_lto_module_to_llvm, submit_pre_lto_module_to_llvm, ComputedLtoType, OngoingCodegen,
 };
 use crate::common::{IntPredicate, RealPredicate, TypeKind};
+use crate::errors;
 use crate::meth;
 use crate::mir;
 use crate::mir::operand::OperandValue;
@@ -451,10 +452,7 @@ fn create_entry_fn<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         let Some(llfn) = cx.declare_c_main(llfty) else {
             // FIXME: We should be smart and show a better diagnostic here.
             let span = cx.tcx().def_span(rust_main_def_id);
-            cx.sess()
+            cx.sess().emit_err(errors::MultipleMainFunctions { span });
-                .struct_span_err(span, "entry symbol `main` declared multiple times")
-                .help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
-                .emit();
             cx.sess().abort_if_errors();
             bug!();
         };
@@ -595,8 +593,8 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
                 &metadata,
                 &exported_symbols::metadata_symbol_name(tcx),
             );
-            if let Err(err) = std::fs::write(&file_name, data) {
+            if let Err(error) = std::fs::write(&file_name, data) {
-                tcx.sess.fatal(&format!("error writing metadata object file: {}", err));
+                tcx.sess.emit_fatal(errors::MetadataObjectFileWrite { error });
             }
             Some(CompiledModule {
                 name: metadata_cgu_name,
@@ -815,11 +813,7 @@ pub fn new(tcx: TyCtxt<'_>, target_cpu: String) -> CrateInfo {
         let subsystem = tcx.sess.first_attr_value_str_by_name(crate_attrs, sym::windows_subsystem);
         let windows_subsystem = subsystem.map(|subsystem| {
             if subsystem != sym::windows && subsystem != sym::console {
-                tcx.sess.fatal(&format!(
+                tcx.sess.emit_fatal(errors::InvalidWindowsSubsystem { subsystem });
-                    "invalid windows subsystem `{}`, only \
-                                     `windows` and `console` are allowed",
-                    subsystem
-                ));
             }
             subsystem.to_string()
         });

compiler/rustc_codegen_ssa/src/errors.rs

@@ -555,3 +555,23 @@ pub struct ExpectedUsedSymbol {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_multiple_main_functions)]
+#[help]
+pub struct MultipleMainFunctions {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_metadata_object_file_write)]
+pub struct MetadataObjectFileWrite {
+    pub error: Error,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_invalid_windows_subsystem)]
+pub struct InvalidWindowsSubsystem {
+    pub subsystem: Symbol,
+}

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

@@ -194,3 +194,10 @@ codegen_ssa_unknown_archive_kind =
     Don't know how to build archive of type: {$kind}
 
 codegen_ssa_expected_used_symbol = expected `used`, `used(compiler)` or `used(linker)`
+
+codegen_ssa_multiple_main_functions = entry symbol `main` declared multiple times
+    .help = did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead
+
+codegen_ssa_metadata_object_file_write = error writing metadata object file: {$error}
+
+codegen_ssa_invalid_windows_subsystem = invalid windows subsystem `{$subsystem}`, only `windows` and `console` are allowed