Rollup merge of #109909 - clubby789:import-tool-mod, r=petrochenkov

Deny `use`ing tool paths

Fixes #109853
Fixes #109147

2 files changed, 16 insertions, 11 deletions

diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index 867363f4246..07aaaa1eb7f 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -470,5 +470,14 @@ pub(crate) struct ExpectedFound {
 pub(crate) struct Indeterminate(#[primary_span] pub(crate) Span);
 
 #[derive(Diagnostic)]
+#[diag(resolve_tool_module_imported)]
+pub(crate) struct ToolModuleImported {
+    #[primary_span]
+    pub(crate) span: Span,
+    #[note]
+    pub(crate) import: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(resolve_module_only)]
 pub(crate) struct ModuleOnly(#[primary_span] pub(crate) Span);
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index 7ff440e49aa..5a56d7b99a9 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -17,7 +17,7 @@ use crate::late::{
     ConstantHasGenerics, ConstantItemKind, HasGenericParams, PathSource, Rib, RibKind,
 };
 use crate::macros::{sub_namespace_match, MacroRulesScope};
-use crate::{AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, Determinacy, Finalize};
+use crate::{errors, AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, Determinacy, Finalize};
 use crate::{Import, ImportKind, LexicalScopeBinding, Module, ModuleKind, ModuleOrUniformRoot};
 use crate::{NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError, Res};
 use crate::{ResolutionError, Resolver, Scope, ScopeSet, Segment, ToNameBinding, Weak};
@@ -1364,7 +1364,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 }
             };
 
-            let is_last = i == path.len() - 1;
+            let is_last = i + 1 == path.len();
             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
             let name = ident.name;
 
@@ -1501,16 +1501,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     if let Some(next_module) = binding.module() {
                         module = Some(ModuleOrUniformRoot::Module(next_module));
                         record_segment_res(self, res);
-                    } else if res == Res::ToolMod && i + 1 != path.len() {
+                    } else if res == Res::ToolMod && !is_last && opt_ns.is_some() {
                         if binding.is_import() {
-                            self.tcx
-                                .sess
-                                .struct_span_err(
-                                    ident.span,
-                                    "cannot use a tool module through an import",
-                                )
-                                .span_note(binding.span, "the tool module imported here")
-                                .emit();
+                            self.tcx.sess.emit_err(errors::ToolModuleImported {
+                                span: ident.span,
+                                import: binding.span,
+                            });
                         }
                         let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
                         return PathResult::NonModule(PartialRes::new(res));