Switch to multipart suggestions.

This commit changes the suggestion so that it is split into multiple
parts in an effort to reduce the impact the applied suggestion could
have on formatting.

src/librustc_resolve/error_reporting.rs

@@ -617,14 +617,12 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
                 _ => format!("{}", ident),
             };
 
-            // Assume this is the easy case of `use issue_59764::foo::makro;` and just remove
-            // intermediate segments.
-            let (mut span, mut correction) = (directive.span,
-                                              format!("{}::{}", module_name, import));
-
-            if directive.is_nested() {
-                span = directive.use_span;
-
+            let mut corrections: Vec<(Span, String)> = Vec::new();
+            if !directive.is_nested() {
+                // Assume this is the easy case of `use issue_59764::foo::makro;` and just remove
+                // intermediate segments.
+                corrections.push((directive.span, format!("{}::{}", module_name, import)));
+            } else {
                 // Find the binding span (and any trailing commas and spaces).
                 //   ie. `use a::b::{c, d, e};`
                 //                      ^^^
@@ -652,6 +650,9 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
                 }
                 debug!("check_for_module_export_macro: removal_span={:?}", removal_span);
 
+                // Remove the `removal_span`.
+                corrections.push((removal_span, "".to_string()));
+
                 // Find the span after the crate name and if it has nested imports immediatately
                 // after the crate name already.
                 //   ie. `use a::b::{c, d};`
@@ -666,34 +667,32 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
 
                 let source_map = self.resolver.session.source_map();
 
-                // Remove two bytes at the end to keep all but the `};` characters.
-                //   ie. `{b::{c, d}, e::{f, g}};`
-                //        ^^^^^^^^^^^^^^^^^^^^^
-                let end_bytes = BytePos(if has_nested { 2 } else { 1 });
-                let mut remaining_span = after_crate_name.with_hi(
-                    after_crate_name.hi() - end_bytes);
-                if has_nested {
-                    // Remove two bytes at the start to keep all but the initial `{` character.
-                    //   ie. `{b::{c, d}, e::{f, g}`
-                    //         ^^^^^^^^^^^^^^^^^^^^
-                    remaining_span = remaining_span.with_lo(after_crate_name.lo() + BytePos(1));
+                // Add the import to the start, with a `{` if required.
+                let start_point = source_map.start_point(after_crate_name);
+                if let Ok(start_snippet) = source_map.span_to_snippet(start_point) {
+                    corrections.push((
+                        start_point,
+                        if has_nested {
+                            // In this case, `start_snippet` must equal '{'.
+                            format!("{}{}, ", start_snippet, import)
+                        } else {
+                            // In this case, add a `{`, then the moved import, then whatever
+                            // was there before.
+                            format!("{{{}, {}", import, start_snippet)
+                        }
+                    ));
                 }
 
-                // Calculate the number of characters into a snippet to remove the removal
-                // span.
-                let lo = removal_span.lo() - remaining_span.lo();
-                let hi = lo + (removal_span.hi() - removal_span.lo());
-                if let Ok(mut remaining) = source_map.span_to_snippet(remaining_span) {
-                    // Remove the original location of the binding.
-                    remaining.replace_range((lo.0 as usize)..(hi.0 as usize), "");
-                    correction = format!("use {}::{{{}, {}}};", module_name, import, remaining);
+                // Add a `};` to the end if nested, matching the `{` added at the start.
+                if !has_nested {
+                    corrections.push((source_map.end_point(after_crate_name),
+                                     "};".to_string()));
                 }
             }
 
             let suggestion = Some((
-                span,
+                corrections,
                 String::from("a macro with this name exists at the root of the crate"),
-                correction,
                 Applicability::MaybeIncorrect,
             ));
             let note = vec![

src/librustc_resolve/lib.rs

@@ -139,8 +139,8 @@ impl Ord for BindingError {
     }
 }
 
-/// A span, message, replacement text, and applicability.
-type Suggestion = (Span, String, String, Applicability);
+/// A vector of spans and replacements, a message and applicability.
+type Suggestion = (Vec<(Span, String)>, String, Applicability);
 
 enum ResolutionError<'a> {
     /// Error E0401: can't use type or const parameters from outer function.
@@ -390,8 +390,8 @@ fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver<'_>,
                                            "failed to resolve: {}", &label);
             err.span_label(span, label);
 
-            if let Some((span, msg, suggestion, applicability)) = suggestion {
-                err.span_suggestion(span, &msg, suggestion, applicability);
+            if let Some((suggestions, msg, applicability)) = suggestion {
+                err.multipart_suggestion(&msg, suggestions, applicability);
             }
 
             err
@@ -3774,9 +3774,8 @@ impl<'a> Resolver<'a> {
                             (
                                 String::from("unresolved import"),
                                 Some((
-                                    ident.span,
+                                    vec![(ident.span, candidate.path.to_string())],
                                     String::from("a similar path exists"),
-                                    candidate.path.to_string(),
                                     Applicability::MaybeIncorrect,
                                 )),
                             )

src/librustc_resolve/resolve_imports.rs

@@ -793,8 +793,8 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
                 diag.span_label(err.span, label);
             }
 
-            if let Some((span, msg, suggestion, applicability)) = err.suggestion {
-                diag.span_suggestion(span, &msg, suggestion, applicability);
+            if let Some((suggestions, msg, applicability)) = err.suggestion {
+                diag.multipart_suggestion(&msg, suggestions, applicability);
             }
         }
 
@@ -947,9 +947,8 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
                                 label: None,
                                 note,
                                 suggestion: Some((
-                                    span,
+                                    vec![(span, Segment::names_to_string(&suggestion))],
                                     String::from("a similar path exists"),
-                                    Segment::names_to_string(&suggestion),
                                     Applicability::MaybeIncorrect,
                                 )),
                             }
@@ -1113,8 +1112,9 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
 
                 let lev_suggestion = find_best_match_for_name(names, &ident.as_str(), None)
                    .map(|suggestion|
-                        (ident.span, String::from("a similar name exists in the module"),
-                         suggestion.to_string(), Applicability::MaybeIncorrect)
+                        (vec![(ident.span, suggestion.to_string())],
+                         String::from("a similar name exists in the module"),
+                         Applicability::MaybeIncorrect)
                     );
 
                 let (suggestion, note) = match self.check_for_module_export_macro(

src/test/ui/issue-59764.rs

@@ -1,7 +1,6 @@
 // aux-build:issue-59764.rs
 // compile-flags:--extern issue_59764
 // edition:2018
-// run-rustfix
 
 #![allow(warnings)]