Handle renamed imports.

This commit extends the suggestion to handle imports that are aliased to
another name.

Author: davidtwco

src/librustc_resolve/error_reporting.rs

@@ -11,7 +11,7 @@ use syntax::symbol::keywords;
 use syntax_pos::Span;
 
 use crate::macros::ParentScope;
-use crate::resolve_imports::{ImportDirective, ImportResolver};
+use crate::resolve_imports::{ImportDirective, ImportDirectiveSubclass, ImportResolver};
 use crate::{import_candidate_to_enum_paths, is_self_type, is_self_value, path_names_to_string};
 use crate::{AssocSuggestion, CrateLint, ImportSuggestion, ModuleOrUniformRoot, PathResult,
             PathSource, Resolver, Segment, Suggestion};
@@ -610,11 +610,16 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
         let resolution = resolutions.get(&(ident, MacroNS))?;
         let binding = resolution.borrow().binding()?;
         if let Def::Macro(_, MacroKind::Bang) = binding.def() {
-            let name = crate_module.kind.name().unwrap();
+            let module_name = crate_module.kind.name().unwrap();
+            let import = match directive.subclass {
+                ImportDirectiveSubclass::SingleImport { source, target, .. } if source != target =>
+                    format!("{} as {}", source, target),
+                _ => format!("{}", ident),
+            };
             let suggestion = Some((
                 directive.span,
                 String::from("a macro with this name exists at the root of the crate"),
-                format!("{}::{}", name, ident),
+                format!("{}::{}", module_name, import),
                 Applicability::MaybeIncorrect,
             ));
             let note = vec![

src/librustc_resolve/resolve_imports.rs

@@ -1111,21 +1111,17 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
                     }
                 });
 
-                let (suggestion, note) = if let Some((suggestion, note)) =
-                    self.check_for_module_export_macro(directive, module, ident)
-                {
-
-                    (
-                        suggestion.or_else(||
-                           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)
-                            )),
-                        note,
-                    )
-                } else {
-                    (None, Vec::new())
+                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)
+                    );
+
+                let (suggestion, note) = match self.check_for_module_export_macro(
+                    directive, module, ident,
+                ) {
+                    Some((suggestion, note)) => (suggestion.or(lev_suggestion), note),
+                    _ => (lev_suggestion, Vec::new()),
                 };
 
                 let label = match module {

src/test/ui/issue-59764.fixed

@@ -3,6 +3,21 @@
 // edition:2018
 // run-rustfix
 
+#![allow(warnings)]
+
+// This tests the suggestion to import macros from the root of a crate. This aims to capture
+// the case where a user attempts to import a macro from the definition location instead of the
+// root of the crate and the macro is annotated with `#![macro_export]`.
+
+// Edge cases..
+
+mod renamed_import {
+    use issue_59764::makro as baz;
+    //~^ ERROR unresolved import `issue_59764::foo::makro` [E0432]
+}
+
+// Simple case..
+
 use issue_59764::makro;
 //~^ ERROR unresolved import `issue_59764::foo::makro` [E0432]
 

src/test/ui/issue-59764.rs

@@ -3,6 +3,21 @@
 // edition:2018
 // run-rustfix
 
+#![allow(warnings)]
+
+// This tests the suggestion to import macros from the root of a crate. This aims to capture
+// the case where a user attempts to import a macro from the definition location instead of the
+// root of the crate and the macro is annotated with `#![macro_export]`.
+
+// Edge cases..
+
+mod renamed_import {
+    use issue_59764::foo::makro as baz;
+    //~^ ERROR unresolved import `issue_59764::foo::makro` [E0432]
+}
+
+// Simple case..
+
 use issue_59764::foo::makro;
 //~^ ERROR unresolved import `issue_59764::foo::makro` [E0432]
 

src/test/ui/issue-59764.stderr

@@ -1,5 +1,17 @@
 error[E0432]: unresolved import `issue_59764::foo::makro`
-  --> $DIR/issue-59764.rs:6:5
+  --> $DIR/issue-59764.rs:15:9
+   |
+LL |     use issue_59764::foo::makro as baz;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `makro` in `foo`
+   |
+   = note: this could be because a macro annotated with `#[macro_export]` will be exported at the root of the crate instead of the module where it is defined
+help: a macro with this name exists at the root of the crate
+   |
+LL |     use issue_59764::makro as baz;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0432]: unresolved import `issue_59764::foo::makro`
+  --> $DIR/issue-59764.rs:21:5
    |
 LL | use issue_59764::foo::makro;
    |     ^^^^^^^^^^^^^^^^^^^^^^^ no `makro` in `foo`
@@ -11,20 +23,20 @@ LL | use issue_59764::makro;
    |     ^^^^^^^^^^^^^^^^^^
 
 error: cannot determine resolution for the macro `makro`
-  --> $DIR/issue-59764.rs:9:1
+  --> $DIR/issue-59764.rs:24:1
    |
 LL | makro!(bar);
    | ^^^^^
    |
    = note: import resolution is stuck, try simplifying macro imports
 
 error[E0425]: cannot find function `bar` in this scope
-  --> $DIR/issue-59764.rs:13:5
+  --> $DIR/issue-59764.rs:28:5
    |
 LL |     bar();
    |     ^^^ not found in this scope
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors occurred: E0425, E0432.
 For more information about an error, try `rustc --explain E0425`.