Auto merge of #46116 - oli-obk:json_ui, r=nikomatsakis

Check //~ERROR comments in ui tests

r? @nikomatsakis

cc #44844 @Phlosioneer @estebank @petrochenkov

this depends on #46052 getting merged first (the commits are included in here)

The relevant changes of this PR are c2f0af7 and 979269b

Author: bors

src/librustc/session/mod.rs

@@ -355,12 +355,15 @@ impl Session {
 
     /// Analogous to calling methods on the given `DiagnosticBuilder`, but
     /// deduplicates on lint ID, span (if any), and message for this `Session`
-    /// if we're not outputting in JSON mode.
     fn diag_once<'a, 'b>(&'a self,
                          diag_builder: &'b mut DiagnosticBuilder<'a>,
                          method: DiagnosticBuilderMethod,
                          lint: &'static lint::Lint, message: &str, span: Option<Span>) {
-        let mut do_method = || {
+
+        let lint_id = DiagnosticMessageId::LintId(lint::LintId::of(lint));
+        let id_span_message = (lint_id, span, message.to_owned());
+        let fresh = self.one_time_diagnostics.borrow_mut().insert(id_span_message);
+        if fresh {
             match method {
                 DiagnosticBuilderMethod::Note => {
                     diag_builder.note(message);
@@ -369,22 +372,6 @@ impl Session {
                     diag_builder.span_note(span.expect("span_note expects a span"), message);
                 }
             }
-        };
-
-        match self.opts.error_format {
-            // when outputting JSON for tool consumption, the tool might want
-            // the duplicates
-            config::ErrorOutputType::Json(_) => {
-                do_method()
-            },
-            _ => {
-                let lint_id = DiagnosticMessageId::LintId(lint::LintId::of(lint));
-                let id_span_message = (lint_id, span, message.to_owned());
-                let fresh = self.one_time_diagnostics.borrow_mut().insert(id_span_message);
-                if fresh {
-                    do_method()
-                }
-            }
         }
     }
 

src/test/compile-fail/issue-31221.rs

@@ -13,8 +13,6 @@
 #![allow(non_snake_case)]
 #![deny(unreachable_patterns)]
 //~^ NOTE lint level defined here
-//~^^ NOTE lint level defined here
-//~^^^ NOTE lint level defined here
 
 #[derive(Clone, Copy)]
 enum Enum {