Rollup merge of rust-lang#132207 - compiler-errors:tweak-res-mod-segment, r=petrochenkov

Store resolution for self and crate root module segments

Let's make sure to record the segment resolution for `self::`, `crate::` and `$crate::`.

I'm actually somewhat surprised that the only diagnostic that uses this is the one that errors on invalid generics on a module segment... but seems strictly more correct regardless, and there may be other diagnostics using these segments resolutions that just haven't been tested for `self`. Also includes a drive-by on `report_prohibit_generics_error`.

Author: matthiaskrgr

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -1106,7 +1106,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     .collect::<String>()
             ),
             [(only, _)] => only.to_string(),
-            [] => "this type".to_string(),
+            [] => bug!("expected one segment to deny"),
         };
 
         let arg_spans: Vec<Span> = segments
@@ -1136,7 +1136,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 "s",
             ),
             [only] => (only.to_string(), ""),
-            [] => unreachable!("expected at least one generic to prohibit"),
+            [] => bug!("expected at least one generic to prohibit"),
         };
         let last_span = *arg_spans.last().unwrap();
         let span: MultiSpan = arg_spans.into();

compiler/rustc_resolve/src/ident.rs

@@ -1478,9 +1478,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 if segment_idx == 0 {
                     if name == kw::SelfLower {
                         let mut ctxt = ident.span.ctxt().normalize_to_macros_2_0();
-                        module = Some(ModuleOrUniformRoot::Module(
-                            self.resolve_self(&mut ctxt, parent_scope.module),
-                        ));
+                        let self_mod = self.resolve_self(&mut ctxt, parent_scope.module);
+                        if let Some(res) = self_mod.res() {
+                            record_segment_res(self, res);
+                        }
+                        module = Some(ModuleOrUniformRoot::Module(self_mod));
                         continue;
                     }
                     if name == kw::PathRoot && ident.span.at_least_rust_2018() {
@@ -1497,7 +1499,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     if name == kw::PathRoot || name == kw::Crate || name == kw::DollarCrate {
                         // `::a::b`, `crate::a::b` or `$crate::a::b`
-                        module = Some(ModuleOrUniformRoot::Module(self.resolve_crate_root(ident)));
+                        let crate_root = self.resolve_crate_root(ident);
+                        if let Some(res) = crate_root.res() {
+                            record_segment_res(self, res);
+                        }
+                        module = Some(ModuleOrUniformRoot::Module(crate_root));
                         continue;
                     }
                 }

tests/ui/generics/generics-on-self-mod-segment.rs

@@ -0,0 +1,18 @@
+struct Ty;
+
+fn self_(_: self::<i32>::Ty) {}
+//~^ ERROR type arguments are not allowed on module `generics_on_self_mod_segment`
+
+fn crate_(_: crate::<i32>::Ty) {}
+//~^ ERROR type arguments are not allowed on module `generics_on_self_mod_segment`
+
+macro_rules! dollar_crate {
+    () => {
+        fn dollar_crate_(_: $crate::<i32>::Ty) {}
+        //~^ ERROR type arguments are not allowed on module `generics_on_self_mod_segment`
+    }
+}
+
+dollar_crate!();
+
+fn main() {}

tests/ui/generics/generics-on-self-mod-segment.stderr

@@ -0,0 +1,32 @@
+error[E0109]: type arguments are not allowed on module `generics_on_self_mod_segment`
+  --> $DIR/generics-on-self-mod-segment.rs:3:20
+   |
+LL | fn self_(_: self::<i32>::Ty) {}
+   |             ----   ^^^ type argument not allowed
+   |             |
+   |             not allowed on module `generics_on_self_mod_segment`
+
+error[E0109]: type arguments are not allowed on module `generics_on_self_mod_segment`
+  --> $DIR/generics-on-self-mod-segment.rs:6:22
+   |
+LL | fn crate_(_: crate::<i32>::Ty) {}
+   |              -----   ^^^ type argument not allowed
+   |              |
+   |              not allowed on module `generics_on_self_mod_segment`
+
+error[E0109]: type arguments are not allowed on module `generics_on_self_mod_segment`
+  --> $DIR/generics-on-self-mod-segment.rs:11:38
+   |
+LL |         fn dollar_crate_(_: $crate::<i32>::Ty) {}
+   |                             ------   ^^^ type argument not allowed
+   |                             |
+   |                             not allowed on module `generics_on_self_mod_segment`
+...
+LL | dollar_crate!();
+   | --------------- in this macro invocation
+   |
+   = note: this error originates in the macro `dollar_crate` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0109`.