WIP: rewrite build_reduced_graph_for_use_tree

Author: mu001999

compiler/rustc_resolve/messages.ftl

@@ -381,15 +381,6 @@ resolve_self_import_only_in_import_list_with_non_empty_prefix =
     `self` import can only appear in an import list with a non-empty prefix
     .label = can only appear in an import list with a non-empty prefix
 
-resolve_self_imports_only_allowed_within =
-    `self` imports are only allowed within a {"{"} {"}"} list
-
-resolve_self_imports_only_allowed_within_multipart_suggestion =
-    alternatively, use the multi-path `use` syntax to import `self`
-
-resolve_self_imports_only_allowed_within_suggestion =
-    consider importing the module directly
-
 resolve_self_in_const_generic_ty =
     cannot use `Self` in const parameter type
 
@@ -463,6 +454,9 @@ resolve_unexpected_res_use_at_op_in_slice_pat_with_range_sugg =
 resolve_unnamed_crate_root_import =
     crate root imports need to be explicitly named: `use crate as name;`
 
+resolve_unnamed_imports =
+    imports need to be explicitly named: `use {$ident} as name;`
+
 resolve_unreachable_label =
     use of unreachable label `{$name}`
     .label = unreachable label `{$name}`

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -596,35 +596,72 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                         }
                     }
                 } else {
-                    // Disallow `self`
-                    if source.ident.name == kw::SelfLower {
-                        let parent = module_path.last();
+                    match source.ident.name {
+                        // Allow `use crate as name;`
+                        kw::Crate => {
+                            if !module_path.is_empty() {
+                                self.r.dcx().span_err(
+                                    ident.span,
+                                    "`crate` in paths can only be used in start position",
+                                );
+                                return;
+                            }
 
-                        let span = match parent {
-                            // only `::self` from `use foo::self as bar`
-                            Some(seg) => seg.ident.span.shrink_to_hi().to(source.ident.span),
-                            None => source.ident.span,
-                        };
-                        let span_with_rename = match rename {
-                            // only `self as bar` from `use foo::self as bar`
-                            Some(rename) => source.ident.span.to(rename.span),
-                            None => source.ident.span,
-                        };
-                        self.r.report_error(
-                            span,
-                            ResolutionError::SelfImportsOnlyAllowedWithin {
-                                root: parent.is_none(),
-                                span_with_rename,
-                            },
-                        );
-
-                        // Error recovery: replace `use foo::self;` with `use foo;`
-                        if let Some(parent) = module_path.pop() {
-                            source = parent;
                             if rename.is_none() {
-                                ident = source.ident;
+                                self.r
+                                    .dcx()
+                                    .emit_err(errors::UnnamedCrateRootImport { span: ident.span });
+                                return;
                             }
                         }
+                        // Allow `use super as name;`
+                        kw::Super => {
+                            if !module_path.is_empty() {
+                                self.r.dcx().span_err(
+                                    ident.span,
+                                    "`super` in paths can only be used in start position",
+                                );
+                                return;
+                            }
+
+                            if rename.is_none() {
+                                self.r
+                                    .dcx()
+                                    .emit_err(errors::UnnamedImports { span: ident.span, ident });
+                                return;
+                            }
+
+                            type_ns_only = true;
+                        }
+                        // Allow `use self as name;`, `use foo::self;` and `use foo::self as name;`
+                        kw::SelfLower => {
+                            if let Some(parent) = module_path.pop() {
+                                if parent.ident.name.is_path_segment_keyword() {
+                                    self.r.report_error(
+                                        source.ident.span,
+                                        ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix,
+                                    );
+                                    return;
+                                }
+
+                                let self_span = source.ident.span;
+                                source = parent;
+                                if rename.is_none() {
+                                    ident = Ident::new(source.ident.name, self_span);
+                                }
+                            } else {
+                                if rename.is_none() {
+                                    self.r.dcx().emit_err(errors::UnnamedImports {
+                                        span: ident.span,
+                                        ident,
+                                    });
+                                    return;
+                                }
+                            }
+                            type_ns_only = true;
+                        }
+                        kw::DollarCrate => {}
+                        _ => {}
                     }
 
                     // Disallow `use $crate;`
@@ -708,6 +745,12 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     }
 
                     e.emit();
+                } else if let &[self_span] = &self_spans[..]
+                    && prefix.len() == 1
+                    && prefix[0].ident.name == kw::DollarCrate
+                {
+                    // Disallow `use $crate::{self};`
+                    self.r.dcx().emit_err(errors::CrateImported { span: self_span });
                 }
 
                 for &(ref tree, id) in items {

compiler/rustc_resolve/src/diagnostics.rs

@@ -867,29 +867,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     sub_unreachable,
                 })
             }
-            ResolutionError::SelfImportsOnlyAllowedWithin { root, span_with_rename } => {
-                // None of the suggestions below would help with a case like `use self`.
-                let (suggestion, mpart_suggestion) = if root {
-                    (None, None)
-                } else {
-                    // use foo::bar::self        -> foo::bar
-                    // use foo::bar::self as abc -> foo::bar as abc
-                    let suggestion = errs::SelfImportsOnlyAllowedWithinSuggestion { span };
-
-                    // use foo::bar::self        -> foo::bar::{self}
-                    // use foo::bar::self as abc -> foo::bar::{self as abc}
-                    let mpart_suggestion = errs::SelfImportsOnlyAllowedWithinMultipartSuggestion {
-                        multipart_start: span_with_rename.shrink_to_lo(),
-                        multipart_end: span_with_rename.shrink_to_hi(),
-                    };
-                    (Some(suggestion), Some(mpart_suggestion))
-                };
-                self.dcx().create_err(errs::SelfImportsOnlyAllowedWithin {
-                    span,
-                    suggestion,
-                    mpart_suggestion,
-                })
-            }
             ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
                 self.dcx().create_err(errs::SelfImportCanOnlyAppearOnceInTheList { span })
             }

compiler/rustc_resolve/src/errors.rs

@@ -272,40 +272,6 @@ pub(crate) struct AttemptToUseNonConstantValueInConstantWithoutSuggestion<'a> {
     pub(crate) suggestion: &'a str,
 }
 
-#[derive(Diagnostic)]
-#[diag(resolve_self_imports_only_allowed_within, code = E0429)]
-pub(crate) struct SelfImportsOnlyAllowedWithin {
-    #[primary_span]
-    pub(crate) span: Span,
-    #[subdiagnostic]
-    pub(crate) suggestion: Option<SelfImportsOnlyAllowedWithinSuggestion>,
-    #[subdiagnostic]
-    pub(crate) mpart_suggestion: Option<SelfImportsOnlyAllowedWithinMultipartSuggestion>,
-}
-
-#[derive(Subdiagnostic)]
-#[suggestion(
-    resolve_self_imports_only_allowed_within_suggestion,
-    code = "",
-    applicability = "machine-applicable"
-)]
-pub(crate) struct SelfImportsOnlyAllowedWithinSuggestion {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[multipart_suggestion(
-    resolve_self_imports_only_allowed_within_multipart_suggestion,
-    applicability = "machine-applicable"
-)]
-pub(crate) struct SelfImportsOnlyAllowedWithinMultipartSuggestion {
-    #[suggestion_part(code = "{{")]
-    pub(crate) multipart_start: Span,
-    #[suggestion_part(code = "}}")]
-    pub(crate) multipart_end: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(resolve_binding_shadows_something_unacceptable, code = E0530)]
 pub(crate) struct BindingShadowsSomethingUnacceptable<'a> {
@@ -898,6 +864,14 @@ pub(crate) struct UnnamedCrateRootImport {
     pub(crate) span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(resolve_unnamed_imports)]
+pub(crate) struct UnnamedImports {
+    #[primary_span]
+    pub(crate) span: Span,
+    pub(crate) ident: Ident,
+}
+
 #[derive(Diagnostic)]
 #[diag(resolve_macro_expanded_extern_crate_cannot_shadow_extern_arguments)]
 pub(crate) struct MacroExpandedExternCrateCannotShadowExternArguments {

compiler/rustc_resolve/src/ident.rs

@@ -869,6 +869,14 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         // FIXME: Implement these with renaming requirements so that e.g.
                         // `use super;` doesn't work, but `use super as name;` does.
                         // Fall through here to get an error from `early_resolve_...`.
+
+                        if ident.name == kw::Super {
+                            if let Some(parent) = parent_scope.module.parent {
+                                return Ok(parent.self_binding.unwrap());
+                            }
+                        } else {
+                            return Ok(parent_scope.module.self_binding.unwrap());
+                        }
                     }
                 }
 

compiler/rustc_resolve/src/lib.rs

@@ -261,8 +261,6 @@ enum ResolutionError<'ra> {
     IdentifierBoundMoreThanOnceInSamePattern(Ident),
     /// Error E0426: use of undeclared label.
     UndeclaredLabel { name: Symbol, suggestion: Option<LabelSuggestion> },
-    /// Error E0429: `self` imports are only allowed within a `{ }` list.
-    SelfImportsOnlyAllowedWithin { root: bool, span_with_rename: Span },
     /// Error E0430: `self` import can only appear once in the list.
     SelfImportCanOnlyAppearOnceInTheList,
     /// Error E0431: `self` import can only appear in an import list with a non-empty prefix.

tests/ui/dollar-crate/use-dollar-crate-self.rs

@@ -0,0 +1,9 @@
+macro_rules! foo {
+    () => {
+        use $crate::{self}; //~ ERROR `$crate` may not be imported
+    };
+}
+
+foo!();
+
+fn main() {}

tests/ui/dollar-crate/use-dollar-crate-self.stderr

@@ -0,0 +1,12 @@
+error: `$crate` may not be imported
+  --> $DIR/use-dollar-crate-self.rs:3:22
+   |
+LL |         use $crate::{self};
+   |                      ^^^^
+...
+LL | foo!();
+   | ------ in this macro invocation
+   |
+   = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error

tests/ui/use/use-path-segment-kw.rs

@@ -0,0 +1,78 @@
+//@ edition: 2021
+
+// mod x {
+//     use super; // bad
+//     use super as name; // good
+//     use self; // bad
+//     use self as name; // good
+//     use crate; // bad
+//     use crate as name; // good
+//     use $crate; // bad
+//     use $crate as name; // good
+
+//     mod foo;
+//     use foo::crate; // bad
+//     use crate::crate; // bad
+//     use foo::super; // bad
+//     use super::super; // bad
+//     use foo::self; // good
+//     use self::self; // bad
+//     use self::self as name; // good
+// }
+
+fn bar() {}
+
+mod foo {
+    pub mod bar {
+        pub mod foobar {
+            pub fn bar() {}
+        }
+    }
+
+    pub use crate as _crate; // Good
+    use crate; //~ ERROR crate root imports need to be explicitly named: `use crate as name;`
+    use ::crate; //~ ERROR `crate` in paths can only be used in start position
+    use bar::crate; //~ ERROR `crate` in paths can only be used in start position
+    use crate::crate; //~ ERROR `crate` in paths can only be used in start position
+    use super::crate; //~ ERROR `crate` in paths can only be used in start position
+    use self::crate; //~ ERROR `crate` in paths can only be used in start position
+    use ::crate as _crate2; //~ ERROR `crate` in paths can only be used in start position
+    use bar::crate as _crate3; //~ ERROR `crate` in paths can only be used in start position
+    use crate::crate as _crate4; //~ ERROR `crate` in paths can only be used in start position
+    use super::crate as _crate5; //~ ERROR `crate` in paths can only be used in start position
+    use self::crate as _crate6; //~ ERROR `crate` in paths can only be used in start position
+
+    pub use super as _super; // Good
+    use super; //~ ERROR imports need to be explicitly named: `use super as name;`
+    use ::super; //~ ERROR `super` in paths can only be used in start position
+    use bar::super; //~ ERROR `super` in paths can only be used in start position
+    use crate::super; //~ ERROR `super` in paths can only be used in start position
+    use super::super; //~ ERROR `super` in paths can only be used in start position
+    use self::super; //~ ERROR `super` in paths can only be used in start position
+    use ::super as _super2; //~ ERROR `super` in paths can only be used in start position
+    use bar::super as _super3; //~ ERROR `super` in paths can only be used in start position
+    use crate::super as _super4; //~ ERROR `super` in paths can only be used in start position
+    use super::super as _super5; //~ ERROR `super` in paths can only be used in start position
+    use bar::super as _super6; //~ ERROR `super` in paths can only be used in start position
+
+    pub use self as _self; // Good
+    use self; //~ ERROR imports need to be explicitly named: `use self as name;`
+    use ::self; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    pub use bar::foobar::self; // Good
+    use crate::self; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    use super::self; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    use self::self; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    use ::self as _self2; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    pub use bar::self as _self3; // Good
+    use crate::self as _self4; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    use super::self as _self5; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+    use self::self as _self6; //~ ERROR `self` import can only appear in an import list with a non-empty prefix
+}
+
+fn main() {
+    foo::_crate::bar();
+    foo::_super::bar();
+    foo::_self::bar::foobar::bar();
+    foo::foobar::bar();
+    foo::_self3::foobar::bar();
+}