Remove unnecessary dummy span checks

The emitter already verifies wether a given span note or span label
can be emitted to the output. If it can't, because it is a dummy
span, it will be either elided for labels or emitted as an unspanned
note/help when applicable.

src/librustc_errors/emitter.rs

@@ -959,7 +959,7 @@ impl EmitterWriter {
             Style::MainHeaderMsg
         };
 
-        if msp.primary_spans().is_empty() && msp.span_labels().is_empty() && is_secondary
+        if !msp.has_primary_spans() && !msp.has_span_labels() && is_secondary
            && !self.short_message {
             // This is a secondary message with no span info
             for _ in 0..max_line_num_len {

src/librustc_resolve/lib.rs

@@ -5013,11 +5013,7 @@ impl<'a> Resolver<'a> {
                 ))
             }
 
-            if b.span.is_dummy() {
+            err.span_note(b.span, &note_msg);
-                err.note(&note_msg);
-            } else {
-                err.span_note(b.span, &note_msg);
-            }
             for (i, help_msg) in help_msgs.iter().enumerate() {
                 let or = if i == 0 { "" } else { "or " };
                 err.help(&format!("{}{}", or, help_msg));
@@ -5132,10 +5128,10 @@ impl<'a> Resolver<'a> {
                           container));
 
         err.span_label(span, format!("`{}` re{} here", name, new_participle));
-        if !old_binding.span.is_dummy() {
+        err.span_label(
-            err.span_label(self.session.source_map().def_span(old_binding.span),
+            self.session.source_map().def_span(old_binding.span),
-                           format!("previous {} of the {} `{}` here", old_noun, old_kind, name));
+            format!("previous {} of the {} `{}` here", old_noun, old_kind, name),
-        }
+        );
 
         // See https://github.com/rust-lang/rust/issues/32354
         if old_binding.is_import() || new_binding.is_import() {

src/libsyntax_pos/lib.rs

@@ -668,6 +668,11 @@ impl MultiSpan {
         &self.primary_spans
     }
 
+    /// Returns wether any of the primary spans is displayable.
+    pub fn has_primary_spans(&self) -> bool {
+        self.primary_spans.iter().any(|sp| *sp != DUMMY_SP)
+    }
+
     /// Returns `true` if this contains only a dummy primary span with any hygienic context.
     pub fn is_dummy(&self) -> bool {
         let mut is_dummy = true;
@@ -726,6 +731,11 @@ impl MultiSpan {
 
         span_labels
     }
+
+    /// Returns wether any of the span labels is displayable.
+    pub fn has_span_labels(&self) -> bool {
+        self.span_labels.iter().any(|(sp, _)| *sp != DUMMY_SP)
+    }
 }
 
 impl From<Span> for MultiSpan {

src/test/ui/consts/const-size_of-cycle.stderr

@@ -9,8 +9,8 @@ note: ...which requires const-evaluating `Foo::bytes::{{constant}}`...
    |
 LL |     intrinsics::size_of::<T>()
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: ...which requires computing layout of `Foo`...
+   = note: ...which requires computing layout of `Foo`...
-note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All, def_id: None }, value: [u8; _] }`...
+   = note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All, def_id: None }, value: [u8; _] }`...
 note: ...which requires const-evaluating + checking `Foo::bytes::{{constant}}`...
   --> $DIR/const-size_of-cycle.rs:6:17
    |

src/test/ui/impl-trait/auto-trait-leak.stderr

@@ -9,7 +9,7 @@ note: ...which requires processing `cycle1`...
    |
 LL | fn cycle1() -> impl Clone {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
-note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
+   = note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
 note: ...which requires processing `cycle2::{{impl-Trait}}`...
   --> $DIR/auto-trait-leak.rs:23:16
    |
@@ -20,7 +20,7 @@ note: ...which requires processing `cycle2`...
    |
 LL | fn cycle2() -> impl Clone {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
-note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
+   = note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
    = note: ...which again requires processing `cycle1::{{impl-Trait}}`, completing the cycle
 note: cycle used when checking item types in top-level module
   --> $DIR/auto-trait-leak.rs:3:1
@@ -45,7 +45,7 @@ note: ...which requires processing `cycle1`...
    |
 LL | fn cycle1() -> impl Clone {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
-note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
+   = note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
 note: ...which requires processing `cycle2::{{impl-Trait}}`...
   --> $DIR/auto-trait-leak.rs:23:16
    |

src/test/ui/issues/issue-26548.stderr

@@ -1,6 +1,6 @@
 error[E0391]: cycle detected when computing layout of `std::option::Option<S>`
    |
-note: ...which requires computing layout of `S`...
+   = note: ...which requires computing layout of `S`...
    = note: ...which again requires computing layout of `std::option::Option<S>`, completing the cycle
 note: cycle used when processing `main`
   --> $DIR/issue-26548.rs:9:1

src/test/ui/issues/issue-44415.stderr

@@ -9,8 +9,8 @@ note: ...which requires const-evaluating `Foo::bytes::{{constant}}`...
    |
 LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: ...which requires computing layout of `Foo`...
+   = note: ...which requires computing layout of `Foo`...
-note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All, def_id: None }, value: [u8; _] }`...
+   = note: ...which requires normalizing `ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: All, def_id: None }, value: [u8; _] }`...
 note: ...which requires const-evaluating + checking `Foo::bytes::{{constant}}`...
   --> $DIR/issue-44415.rs:6:17
    |