resolve: Remove artificial import ambiguity errors

compiler/rustc_resolve/src/diagnostics.rs

@@ -1403,7 +1403,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         for ns in [Namespace::MacroNS, Namespace::TypeNS, Namespace::ValueNS] {
             if let Ok(binding) = self.early_resolve_ident_in_lexical_scope(
                 ident,
-                ScopeSet::All(ns, false),
+                ScopeSet::All(ns),
                 &parent_scope,
                 None,
                 false,
@@ -1841,10 +1841,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         _ => None,
                     }
                 } else {
-                    let scopes = ScopeSet::All(ns_to_try, opt_ns.is_none());
                     self.early_resolve_ident_in_lexical_scope(
                         ident,
-                        scopes,
+                        ScopeSet::All(ns_to_try),
                         parent_scope,
                         None,
                         false,

compiler/rustc_resolve/src/ident.rs

@@ -88,7 +88,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
         let rust_2015 = ctxt.edition().is_rust_2015();
         let (ns, macro_kind, is_absolute_path) = match scope_set {
-            ScopeSet::All(ns, _) => (ns, None, false),
+            ScopeSet::All(ns) => (ns, None, false),
             ScopeSet::AbsolutePath(ns) => (ns, None, true),
             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
             ScopeSet::Late(ns, ..) => (ns, None, false),
@@ -397,11 +397,11 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             return Err(Determinacy::Determined);
         }
 
-        let (ns, macro_kind, is_import) = match scope_set {
-            ScopeSet::All(ns, is_import) => (ns, None, is_import),
-            ScopeSet::AbsolutePath(ns) => (ns, None, false),
-            ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
-            ScopeSet::Late(ns, ..) => (ns, None, false),
+        let (ns, macro_kind) = match scope_set {
+            ScopeSet::All(ns) => (ns, None),
+            ScopeSet::AbsolutePath(ns) => (ns, None),
+            ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind)),
+            ScopeSet::Late(ns, ..) => (ns, None),
         };
 
         // This is *the* result, resolution from the scope closest to the resolved identifier.
@@ -631,9 +631,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                 let derive_helper_compat =
                                     Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat);
 
-                                let ambiguity_error_kind = if is_import {
-                                    Some(AmbiguityKind::Import)
-                                } else if is_builtin(innermost_res) || is_builtin(res) {
+                                let ambiguity_error_kind = if is_builtin(innermost_res)
+                                    || is_builtin(res)
+                                {
                                     Some(AmbiguityKind::BuiltinAttr)
                                 } else if innermost_res == derive_helper_compat
                                     || res == derive_helper_compat && innermost_res != derive_helper
@@ -853,10 +853,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     }
                 }
 
-                let scopes = ScopeSet::All(ns, true);
                 let binding = self.early_resolve_ident_in_lexical_scope(
                     ident,
-                    scopes,
+                    ScopeSet::All(ns),
                     parent_scope,
                     finalize,
                     finalize.is_some(),
@@ -1497,7 +1496,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             } else {
                 self.early_resolve_ident_in_lexical_scope(
                     ident,
-                    ScopeSet::All(ns, opt_ns.is_none()),
+                    ScopeSet::All(ns),
                     parent_scope,
                     finalize,
                     finalize.is_some(),

compiler/rustc_resolve/src/imports.rs

@@ -10,10 +10,7 @@ use crate::errors::{
 use crate::Determinacy::{self, *};
 use crate::{fluent_generated as fluent, Namespace::*};
 use crate::{module_to_string, names_to_string, ImportSuggestion};
-use crate::{
-    AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingKey, ModuleKind, ResolutionError,
-    Resolver, Segment,
-};
+use crate::{AmbiguityKind, BindingKey, ModuleKind, ResolutionError, Resolver, Segment};
 use crate::{Finalize, Module, ModuleOrUniformRoot, ParentScope, PerNS, ScopeSet};
 use crate::{NameBinding, NameBindingKind, PathResult};
 
@@ -984,7 +981,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 match binding {
                     Ok(binding) => {
                         // Consistency checks, analogous to `finalize_macro_resolutions`.
-                        let initial_binding = source_bindings[ns].get().map(|initial_binding| {
+                        let initial_res = source_bindings[ns].get().map(|initial_binding| {
                             all_ns_err = false;
                             if let Some(target_binding) = target_bindings[ns].get() {
                                 if target.name == kw::Underscore
@@ -998,20 +995,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                     );
                                 }
                             }
-                            initial_binding
+                            initial_binding.res()
                         });
                         let res = binding.res();
-                        if let Ok(initial_binding) = initial_binding {
-                            let initial_res = initial_binding.res();
+                        if let Ok(initial_res) = initial_res {
                             if res != initial_res && this.ambiguity_errors.is_empty() {
-                                this.ambiguity_errors.push(AmbiguityError {
-                                    kind: AmbiguityKind::Import,
-                                    ident,
-                                    b1: initial_binding,
-                                    b2: binding,
-                                    misc1: AmbiguityErrorMisc::None,
-                                    misc2: AmbiguityErrorMisc::None,
-                                });
+                                span_bug!(import.span, "inconsistent resolution for an import");
                             }
                         } else if res != Res::Err
                             && this.ambiguity_errors.is_empty()
@@ -1283,7 +1272,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
                 match this.early_resolve_ident_in_lexical_scope(
                     target,
-                    ScopeSet::All(ns, false),
+                    ScopeSet::All(ns),
                     &import.parent_scope,
                     None,
                     false,

compiler/rustc_resolve/src/lib.rs

@@ -131,7 +131,7 @@ enum Scope<'a> {
 #[derive(Clone, Copy)]
 enum ScopeSet<'a> {
     /// All scopes with the given namespace.
-    All(Namespace, /*is_import*/ bool),
+    All(Namespace),
     /// Crate root, then extern prelude (used for mixed 2015-2018 mode in macros).
     AbsolutePath(Namespace),
     /// All scopes with macro namespace and the given macro kind restriction.
@@ -718,7 +718,6 @@ struct UseError<'a> {
 
 #[derive(Clone, Copy, PartialEq, Debug)]
 enum AmbiguityKind {
-    Import,
     BuiltinAttr,
     DeriveHelper,
     MacroRulesVsModularized,
@@ -731,7 +730,6 @@ enum AmbiguityKind {
 impl AmbiguityKind {
     fn descr(self) -> &'static str {
         match self {
-            AmbiguityKind::Import => "multiple potential import sources",
             AmbiguityKind::BuiltinAttr => "a name conflict with a builtin attribute",
             AmbiguityKind::DeriveHelper => "a name conflict with a derive helper attribute",
             AmbiguityKind::MacroRulesVsModularized => {
@@ -1557,7 +1555,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             }
         }
 
-        self.visit_scopes(ScopeSet::All(TypeNS, false), parent_scope, ctxt, |this, scope, _, _| {
+        self.visit_scopes(ScopeSet::All(TypeNS), parent_scope, ctxt, |this, scope, _, _| {
             match scope {
                 Scope::Module(module, _) => {
                     this.traits_in_module(module, assoc_item, &mut found_traits);

compiler/rustc_resolve/src/macros.rs

@@ -645,7 +645,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
             res
         } else {
-            let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
+            let scope_set = kind.map_or(ScopeSet::All(MacroNS), ScopeSet::Macro);
             let binding = self.early_resolve_ident_in_lexical_scope(
                 path[0].ident,
                 scope_set,

tests/ui/imports/issue-56125.stderr

@@ -22,47 +22,50 @@ error[E0659]: `issue_56125` is ambiguous
 LL |     use issue_56125::last_segment::*;
    |         ^^^^^^^^^^^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of a conflict between a name from a glob import and an outer scope during import or macro resolution
    = note: `issue_56125` could refer to a crate passed with `--extern`
    = help: use `::issue_56125` to refer to this crate unambiguously
 note: `issue_56125` could also refer to the module imported here
   --> $DIR/issue-56125.rs:6:9
    |
 LL |     use issue_56125::last_segment::*;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = help: use `self::issue_56125` to refer to this module unambiguously
+   = help: consider adding an explicit import of `issue_56125` to disambiguate
+   = help: or use `self::issue_56125` to refer to this module unambiguously
 
 error[E0659]: `issue_56125` is ambiguous
   --> $DIR/issue-56125.rs:11:9
    |
 LL |     use issue_56125::non_last_segment::non_last_segment::*;
    |         ^^^^^^^^^^^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of a conflict between a name from a glob import and an outer scope during import or macro resolution
    = note: `issue_56125` could refer to a crate passed with `--extern`
    = help: use `::issue_56125` to refer to this crate unambiguously
 note: `issue_56125` could also refer to the module imported here
   --> $DIR/issue-56125.rs:11:9
    |
 LL |     use issue_56125::non_last_segment::non_last_segment::*;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = help: use `self::issue_56125` to refer to this module unambiguously
+   = help: consider adding an explicit import of `issue_56125` to disambiguate
+   = help: or use `self::issue_56125` to refer to this module unambiguously
 
 error[E0659]: `issue_56125` is ambiguous
   --> $DIR/issue-56125.rs:18:9
    |
 LL |     use issue_56125::*;
    |         ^^^^^^^^^^^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of a conflict between a name from a glob import and an outer scope during import or macro resolution
    = note: `issue_56125` could refer to a crate passed with `--extern`
    = help: use `::issue_56125` to refer to this crate unambiguously
 note: `issue_56125` could also refer to the module imported here
   --> $DIR/issue-56125.rs:18:9
    |
 LL |     use issue_56125::*;
    |         ^^^^^^^^^^^^^^
-   = help: use `self::issue_56125` to refer to this module unambiguously
+   = help: consider adding an explicit import of `issue_56125` to disambiguate
+   = help: or use `self::issue_56125` to refer to this module unambiguously
 
 error: aborting due to 4 previous errors
 

tests/ui/imports/issue-57539.stderr

@@ -4,15 +4,16 @@ error[E0659]: `core` is ambiguous
 LL |     use core;
    |         ^^^^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of a conflict between a name from a glob import and an outer scope during import or macro resolution
    = note: `core` could refer to a built-in crate
    = help: use `::core` to refer to this crate unambiguously
 note: `core` could also refer to the module imported here
   --> $DIR/issue-57539.rs:5:9
    |
 LL |     use crate::*;
    |         ^^^^^^^^
-   = help: use `self::core` to refer to this module unambiguously
+   = help: consider adding an explicit import of `core` to disambiguate
+   = help: or use `self::core` to refer to this module unambiguously
 
 error: aborting due to previous error
 

tests/ui/proc-macro/derive-helper-shadowing.rs

@@ -23,7 +23,7 @@ macro_rules! gen_helper_use {
 struct S {
     #[empty_helper] // OK, no ambiguity, derive helpers have highest priority
     field: [u8; {
-        use empty_helper; //~ ERROR `empty_helper` is ambiguous
+        use empty_helper; // OK, no ambiguity, derive helpers have highest priority
 
         #[empty_helper] // OK, no ambiguity, derive helpers have highest priority
         struct U;

tests/ui/proc-macro/derive-helper-shadowing.stderr

@@ -37,25 +37,6 @@ help: consider importing this attribute macro through its public re-export
 LL +             use crate::empty_helper;
    |
 
-error[E0659]: `empty_helper` is ambiguous
-  --> $DIR/derive-helper-shadowing.rs:26:13
-   |
-LL |         use empty_helper;
-   |             ^^^^^^^^^^^^ ambiguous name
-   |
-   = note: ambiguous because of multiple potential import sources
-note: `empty_helper` could refer to the derive helper attribute defined here
-  --> $DIR/derive-helper-shadowing.rs:22:10
-   |
-LL | #[derive(Empty)]
-   |          ^^^^^
-note: `empty_helper` could also refer to the attribute macro imported here
-  --> $DIR/derive-helper-shadowing.rs:10:5
-   |
-LL | use test_macros::empty_attr as empty_helper;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = help: use `crate::empty_helper` to refer to this attribute macro unambiguously
-
 error[E0659]: `empty_helper` is ambiguous
   --> $DIR/derive-helper-shadowing.rs:19:3
    |
@@ -88,6 +69,6 @@ LL | #[derive(Empty)]
    = note: for more information, see issue #79202 <https://github.com/rust-lang/rust/issues/79202>
    = note: `#[warn(legacy_derive_helpers)]` on by default
 
-error: aborting due to 5 previous errors; 1 warning emitted
+error: aborting due to 4 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0659`.

tests/ui/rust-2018/uniform-paths/ambiguity-macros-nested.stderr

@@ -4,7 +4,7 @@ error[E0659]: `std` is ambiguous
 LL |     pub use std::io;
    |             ^^^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of a conflict between a macro-expanded name and a less macro-expanded name from outer scope during import or macro resolution
    = note: `std` could refer to a built-in crate
    = help: use `::std` to refer to this crate unambiguously
 note: `std` could also refer to the module defined here

tests/ui/rust-2018/uniform-paths/ambiguity-macros.stderr

@@ -4,7 +4,7 @@ error[E0659]: `std` is ambiguous
 LL | use std::io;
    |     ^^^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of a conflict between a macro-expanded name and a less macro-expanded name from outer scope during import or macro resolution
    = note: `std` could refer to a built-in crate
    = help: use `::std` to refer to this crate unambiguously
 note: `std` could also refer to the module defined here

tests/ui/rust-2018/uniform-paths/ambiguity-nested.rs

@@ -1,12 +1,12 @@
+// check-pass
 // edition:2018
 
 // This test is similar to `ambiguity.rs`, but nested in a module.
 
 #![allow(non_camel_case_types)]
 
 mod foo {
-    pub use std::io;
-    //~^ ERROR `std` is ambiguous
+    pub use std::io; // OK
 
     mod std {
         pub struct io;

tests/ui/rust-2018/uniform-paths/ambiguity.rs

@@ -1,9 +1,9 @@
+// check-pass
 // edition:2018
 
 #![allow(non_camel_case_types)]
 
-use std::io;
-//~^ ERROR `std` is ambiguous
+use std::io; // OK
 
 mod std {
     pub struct io;

tests/ui/rust-2018/uniform-paths/block-scoped-shadow-nested.rs

@@ -1,3 +1,4 @@
+// check-pass
 // edition:2018
 
 mod my {
@@ -13,7 +14,7 @@ mod sub {
 fn foo() {
     use my::sub;
     {
-        use sub::bar; //~ ERROR `sub` is ambiguous
+        use sub::bar; // OK
     }
 }