Addressing feedback

Author: kper

compiler/rustc_errors/src/diagnostic.rs

@@ -567,6 +567,11 @@ impl Diagnostic {
         style: SuggestionStyle,
     ) -> &mut Self {
         assert!(!suggestion.is_empty());
+        debug_assert!(
+            !(suggestion.iter().any(|(sp, text)| sp.lo() == sp.hi() && text.is_empty())),
+            "Span must not be empty and have no suggestion"
+        );
+
         self.push_suggestion(CodeSuggestion {
             substitutions: vec![Substitution {
                 parts: suggestion
@@ -644,6 +649,10 @@ impl Diagnostic {
         applicability: Applicability,
         style: SuggestionStyle,
     ) -> &mut Self {
+        debug_assert!(
+            !(sp.lo() == sp.hi() && suggestion.to_string().is_empty()),
+            "Span must not be empty and have no suggestion"
+        );
         self.push_suggestion(CodeSuggestion {
             substitutions: vec![Substitution {
                 parts: vec![SubstitutionPart { snippet: suggestion.to_string(), span: sp }],
@@ -684,6 +693,12 @@ impl Diagnostic {
     ) -> &mut Self {
         let mut suggestions: Vec<_> = suggestions.collect();
         suggestions.sort();
+
+        debug_assert!(
+            !(sp.lo() == sp.hi() && suggestions.iter().any(|suggestion| suggestion.is_empty())),
+            "Span must not be empty and have no suggestion"
+        );
+
         let substitutions = suggestions
             .into_iter()
             .map(|snippet| Substitution { parts: vec![SubstitutionPart { snippet, span: sp }] })
@@ -705,8 +720,18 @@ impl Diagnostic {
         suggestions: impl Iterator<Item = Vec<(Span, String)>>,
         applicability: Applicability,
     ) -> &mut Self {
+        let suggestions: Vec<_> = suggestions.collect();
+        debug_assert!(
+            !(suggestions
+                .iter()
+                .flat_map(|suggs| suggs)
+                .any(|(sp, suggestion)| sp.lo() == sp.hi() && suggestion.is_empty())),
+            "Span must not be empty and have no suggestion"
+        );
+
         self.push_suggestion(CodeSuggestion {
             substitutions: suggestions
+                .into_iter()
                 .map(|sugg| Substitution {
                     parts: sugg
                         .into_iter()

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -3051,24 +3051,27 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     .map_or(false, |s| s.trim_end().ends_with('<'));
 
             let is_global = poly_trait_ref.trait_ref.path.is_global();
-            let sugg = Vec::from_iter([
-                (
-                    self_ty.span.shrink_to_lo(),
-                    format!(
-                        "{}dyn {}",
-                        if needs_bracket { "<" } else { "" },
-                        if is_global { "(" } else { "" },
-                    ),
+
+            let mut sugg = Vec::from_iter([(
+                self_ty.span.shrink_to_lo(),
+                format!(
+                    "{}dyn {}",
+                    if needs_bracket { "<" } else { "" },
+                    if is_global { "(" } else { "" },
                 ),
-                (
+            )]);
+
+            if is_global || needs_bracket {
+                sugg.push((
                     self_ty.span.shrink_to_hi(),
                     format!(
                         "{}{}",
                         if is_global { ")" } else { "" },
                         if needs_bracket { ">" } else { "" },
                     ),
-                ),
-            ]);
+                ));
+            }
+
             if self_ty.span.edition() >= Edition::Edition2021 {
                 let msg = "trait objects must include the `dyn` keyword";
                 let label = "add `dyn` keyword before this trait";