Rollup merge of #64054 - estebank:unused-import-is-to-eager, r=petrochenkov

Always emit unresolved import errors and hide unused import lint

Fix https://github.com/rust-lang/rust/issues/63724.

r? @petrochenkov

src/librustc_resolve/resolve_imports.rs

@@ -71,7 +71,7 @@ pub enum ImportDirectiveSubclass<'a> {
 }
 
 /// One import directive.
-#[derive(Debug,Clone)]
+#[derive(Debug, Clone)]
 crate struct ImportDirective<'a> {
     /// The ID of the `extern crate`, `UseTree` etc that imported this `ImportDirective`.
     ///
@@ -447,12 +447,13 @@ impl<'a> Resolver<'a> {
     }
 
     // Define the name or return the existing binding if there is a collision.
-    pub fn try_define(&mut self,
+    pub fn try_define(
-                      module: Module<'a>,
+        &mut self,
-                      ident: Ident,
+        module: Module<'a>,
-                      ns: Namespace,
+        ident: Ident,
-                      binding: &'a NameBinding<'a>)
+        ns: Namespace,
-                      -> Result<(), &'a NameBinding<'a>> {
+        binding: &'a NameBinding<'a>,
+    ) -> Result<(), &'a NameBinding<'a>> {
         let res = binding.res();
         self.check_reserved_macro_name(ident, res);
         self.set_binding_parent_module(binding, module);
@@ -480,8 +481,11 @@ impl<'a> Resolver<'a> {
                         };
                         if glob_binding.res() != nonglob_binding.res() &&
                            ns == MacroNS && nonglob_binding.expansion != ExpnId::root() {
-                            resolution.binding = Some(this.ambiguity(AmbiguityKind::GlobVsExpanded,
+                            resolution.binding = Some(this.ambiguity(
-                                                                    nonglob_binding, glob_binding));
+                                AmbiguityKind::GlobVsExpanded,
+                                nonglob_binding,
+                                glob_binding,
+                            ));
                         } else {
                             resolution.binding = Some(nonglob_binding);
                         }
@@ -513,9 +517,11 @@ impl<'a> Resolver<'a> {
         })
     }
 
-    fn ambiguity(&self, kind: AmbiguityKind,
+    fn ambiguity(
-                 primary_binding: &'a NameBinding<'a>, secondary_binding: &'a NameBinding<'a>)
+        &self, kind: AmbiguityKind,
-                 -> &'a NameBinding<'a> {
+        primary_binding: &'a NameBinding<'a>,
+        secondary_binding: &'a NameBinding<'a>,
+    ) -> &'a NameBinding<'a> {
         self.arenas.alloc_name_binding(NameBinding {
             ambiguity: Some((secondary_binding, kind)),
             ..primary_binding.clone()
@@ -524,8 +530,12 @@ impl<'a> Resolver<'a> {
 
     // Use `f` to mutate the resolution of the name in the module.
     // If the resolution becomes a success, define it in the module's glob importers.
-    fn update_resolution<T, F>(&mut self, module: Module<'a>, ident: Ident, ns: Namespace, f: F)
+    fn update_resolution<T, F>(
-                               -> T
+        &mut self, module: Module<'a>,
+        ident: Ident,
+        ns: Namespace,
+        f: F,
+    ) -> T
         where F: FnOnce(&mut Resolver<'a>, &mut NameResolution<'a>) -> T
     {
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
@@ -627,14 +637,18 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
             self.finalize_resolutions_in(module);
         }
 
-        let mut has_errors = false;
         let mut seen_spans = FxHashSet::default();
         let mut errors = vec![];
         let mut prev_root_id: NodeId = NodeId::from_u32(0);
-        for i in 0 .. self.r.determined_imports.len() {
+        let determined_imports = mem::take(&mut self.r.determined_imports);
-            let import = self.r.determined_imports[i];
+        let indeterminate_imports = mem::take(&mut self.r.indeterminate_imports);
+
+        for (is_indeterminate, import) in determined_imports
+            .into_iter()
+            .map(|i| (false, i))
+            .chain(indeterminate_imports.into_iter().map(|i| (true, i)))
+        {
             if let Some(err) = self.finalize_import(import) {
-                has_errors = true;
 
                 if let SingleImport { source, ref source_bindings, .. } = import.subclass {
                     if source.name == kw::SelfLower {
@@ -666,25 +680,27 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                     errors.push((path, err));
                     prev_root_id = import.root_id;
                 }
+            } else if is_indeterminate {
+                // Consider erroneous imports used to avoid duplicate diagnostics.
+                self.r.used_imports.insert((import.id, TypeNS));
+                let path = import_path_to_string(
+                    &import.module_path.iter().map(|seg| seg.ident).collect::<Vec<_>>(),
+                    &import.subclass,
+                    import.span,
+                );
+                let err = UnresolvedImportError {
+                    span: import.span,
+                    label: None,
+                    note: Vec::new(),
+                    suggestion: None,
+                };
+                errors.push((path, err));
             }
         }
 
         if !errors.is_empty() {
             self.throw_unresolved_import_error(errors.clone(), None);
         }
-
-        for import in &self.r.indeterminate_imports {
-            // Consider erroneous imports used to avoid duplicate diagnostics.
-            self.r.used_imports.insert((import.id, TypeNS));
-        }
-        // Report unresolved imports only if no hard error was already reported
-        // to avoid generating multiple errors on the same import.
-        if !has_errors {
-            for import in &self.r.indeterminate_imports {
-                self.throw_unresolved_import_error(errors, Some(MultiSpan::from(import.span)));
-                break;
-            }
-        }
     }
 
     fn throw_unresolved_import_error(
@@ -839,8 +855,14 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
     ) -> Option<UnresolvedImportError> {
         let orig_vis = directive.vis.replace(ty::Visibility::Invisible);
         let prev_ambiguity_errors_len = self.r.ambiguity_errors.len();
-        let path_res = self.r.resolve_path(&directive.module_path, None, &directive.parent_scope,
+        let path_res = self.r.resolve_path(
-                                         true, directive.span, directive.crate_lint());
+            &directive.module_path,
+            None,
+            &directive.parent_scope,
+            true,
+            directive.span,
+            directive.crate_lint(),
+        );
         let no_ambiguity = self.r.ambiguity_errors.len() == prev_ambiguity_errors_len;
         directive.vis.set(orig_vis);
         if let PathResult::Failed { .. } | PathResult::NonModule(..) = path_res {
@@ -903,7 +925,6 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                             }
                         }
                     };
-
                     return Some(err);
                 }
                 return None;

src/test/ui/extenv/issue-55897.rs

@@ -1,7 +1,7 @@
 use prelude::*; //~ ERROR unresolved import `prelude`
 
 mod unresolved_env {
-    use env;
+    use env; //~ ERROR unresolved import `env`
 
     include!(concat!(env!("NON_EXISTENT"), "/data.rs"));
     //~^ ERROR cannot determine resolution for the macro `env`

src/test/ui/extenv/issue-55897.stderr

@@ -19,6 +19,12 @@ LL | use prelude::*;
    |     unresolved import
    |     help: a similar path exists: `std::prelude`
 
+error[E0432]: unresolved import `env`
+  --> $DIR/issue-55897.rs:4:9
+   |
+LL |     use env;
+   |         ^^^ no `env` in the root
+
 error: cannot determine resolution for the macro `env`
   --> $DIR/issue-55897.rs:6:22
    |
@@ -27,6 +33,6 @@ LL |     include!(concat!(env!("NON_EXISTENT"), "/data.rs"));
    |
    = note: import resolution is stuck, try simplifying macro imports
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0432`.

src/test/ui/imports/unresolved-imports-used.rs

@@ -8,11 +8,11 @@ mod qux {
 
 use qux::quz;  //~ ERROR function `quz` is private
 use qux::bar;  //~ ERROR unresolved import `qux::bar`
-use foo::bar;
+use foo::bar;  //~ ERROR unresolved import `foo`
-use baz::*;
+use baz::*;    //~ ERROR unresolved import `baz`
 use qux::bar2; //~ ERROR unresolved import `qux::bar2`
-use foo2::bar2;
+use foo2::bar2;//~ ERROR unresolved import `foo2`
-use baz2::*;
+use baz2::*;   //~ ERROR unresolved import `baz2`
 use qux::quy;  //~ ERROR unused import
 
 fn main() {}

src/test/ui/imports/unresolved-imports-used.stderr

@@ -10,6 +10,30 @@ error[E0432]: unresolved import `qux::bar2`
 LL | use qux::bar2;
    |     ^^^^^^^^^ no `bar2` in `qux`
 
+error[E0432]: unresolved import `foo`
+  --> $DIR/unresolved-imports-used.rs:11:5
+   |
+LL | use foo::bar;
+   |     ^^^ maybe a missing crate `foo`?
+
+error[E0432]: unresolved import `baz`
+  --> $DIR/unresolved-imports-used.rs:12:5
+   |
+LL | use baz::*;
+   |     ^^^ maybe a missing crate `baz`?
+
+error[E0432]: unresolved import `foo2`
+  --> $DIR/unresolved-imports-used.rs:14:5
+   |
+LL | use foo2::bar2;
+   |     ^^^^ maybe a missing crate `foo2`?
+
+error[E0432]: unresolved import `baz2`
+  --> $DIR/unresolved-imports-used.rs:15:5
+   |
+LL | use baz2::*;
+   |     ^^^^ maybe a missing crate `baz2`?
+
 error[E0603]: function `quz` is private
   --> $DIR/unresolved-imports-used.rs:9:10
    |
@@ -28,7 +52,7 @@ note: lint level defined here
 LL | #![deny(unused_imports)]
    |         ^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0432, E0603.
 For more information about an error, try `rustc --explain E0432`.

src/test/ui/rust-2018/uniform-paths/deadlock.rs

@@ -1,7 +1,7 @@
 // edition:2018
 // compile-flags:--extern foo --extern bar
 
-use foo::bar; //~ ERROR unresolved import
+use foo::bar; //~ ERROR can't find crate for `foo`
 use bar::foo;
 
 fn main() {}

src/test/ui/rust-2018/uniform-paths/deadlock.stderr

@@ -1,9 +1,9 @@
-error[E0432]: unresolved import
+error[E0463]: can't find crate for `foo`
   --> $DIR/deadlock.rs:4:5
    |
 LL | use foo::bar;
-   |     ^^^^^^^^
+   |     ^^^ can't find crate
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0432`.
+For more information about this error, try `rustc --explain E0463`.