Fix associated type errors too

compiler/rustc_hir_analysis/messages.ftl

@@ -620,6 +620,8 @@ hir_analysis_variances_of = {$variances}
 hir_analysis_where_clause_on_main = `main` function is not allowed to have a `where` clause
     .label = `main` cannot have a `where` clause
 
+hir_analysis_within_macro = due to this macro variable
+
 hir_analysis_wrong_number_of_generic_arguments_to_intrinsic =
     intrinsic has wrong number of {$descr} parameters: found {$found}, expected {$expected}
     .label = expected {$expected} {$descr} {$expected ->

compiler/rustc_hir_analysis/src/errors.rs

@@ -84,6 +84,8 @@ pub(crate) struct AssocItemNotFound<'a> {
     pub label: Option<AssocItemNotFoundLabel<'a>>,
     #[subdiagnostic]
     pub sugg: Option<AssocItemNotFoundSugg<'a>>,
+    #[label(hir_analysis_within_macro)]
+    pub within_macro_span: Option<Span>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -151,6 +151,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             qself: &qself_str,
             label: None,
             sugg: None,
+            // Try to get the span of the identifier within the path's syntax context
+            // (if that's different).
+            within_macro_span: assoc_name.span.within_macro(span),
         };
 
         if is_dummy {

tests/ui/associated-types/ident-from-macro-expansion.rs

@@ -0,0 +1,23 @@
+trait Trait {}
+impl Trait for () {}
+
+macro_rules! fully_qualified {
+    ($id:ident) => {
+        <() as Trait>::$id
+    }
+}
+
+macro_rules! type_dependent {
+    ($t:ident, $id:ident) => {
+        T::$id
+    }
+}
+
+fn t<T: Trait>() {
+    let x: fully_qualified!(Assoc);
+    //~^ ERROR cannot find associated type `Assoc` in trait `Trait`
+    let x: type_dependent!(T, Assoc);
+    //~^ ERROR associated type `Assoc` not found for `T`
+}
+
+fn main() {}

tests/ui/associated-types/ident-from-macro-expansion.stderr

@@ -0,0 +1,22 @@
+error[E0576]: cannot find associated type `Assoc` in trait `Trait`
+  --> $DIR/ident-from-macro-expansion.rs:17:29
+   |
+LL |         <() as Trait>::$id
+   |                        --- due to this macro variable
+...
+LL |     let x: fully_qualified!(Assoc);
+   |                             ^^^^^ not found in `Trait`
+
+error[E0220]: associated type `Assoc` not found for `T`
+  --> $DIR/ident-from-macro-expansion.rs:19:31
+   |
+LL |         T::$id
+   |            --- due to this macro variable
+...
+LL |     let x: type_dependent!(T, Assoc);
+   |                               ^^^^^ associated type `Assoc` not found
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0220, E0576.
+For more information about an error, try `rustc --explain E0220`.