Store indices of generic args instead of spans, as the actual entries are unused, just the number of entries is checked.

The indices will be used in a follow-up commit

Author: oli-obk

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -702,7 +702,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     pub(crate) fn complain_about_missing_assoc_tys(
         &self,
         associated_types: FxIndexMap<Span, FxIndexSet<DefId>>,
-        potential_assoc_types: Vec<Span>,
+        potential_assoc_types: Vec<usize>,
         trait_bounds: &[hir::PolyTraitRef<'_>],
     ) {
         if associated_types.values().all(|v| v.is_empty()) {

compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs

@@ -474,16 +474,9 @@ pub(crate) fn check_generic_arg_count(
             return Ok(());
         }
 
-        if provided_args > max_expected_args {
-            invalid_args.extend(
-                gen_args.args[max_expected_args..provided_args].iter().map(|arg| arg.span()),
-            );
-        };
+        invalid_args.extend(min_expected_args..provided_args);
 
         let gen_args_info = if provided_args > min_expected_args {
-            invalid_args.extend(
-                gen_args.args[min_expected_args..provided_args].iter().map(|arg| arg.span()),
-            );
             let num_redundant_args = provided_args - min_expected_args;
             GenericArgsInfo::ExcessLifetimes { num_redundant_args }
         } else {
@@ -538,11 +531,7 @@ pub(crate) fn check_generic_arg_count(
         let num_default_params = expected_max - expected_min;
 
         let gen_args_info = if provided > expected_max {
-            invalid_args.extend(
-                gen_args.args[args_offset + expected_max..args_offset + provided]
-                    .iter()
-                    .map(|arg| arg.span()),
-            );
+            invalid_args.extend((expected_max..provided).map(|i| i + args_offset));
             let num_redundant_args = provided - expected_max;
 
             // Provide extra note if synthetic arguments like `impl Trait` are specified.

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -218,8 +218,8 @@ pub(crate) enum GenericArgPosition {
 #[derive(Clone, Debug)]
 pub struct GenericArgCountMismatch {
     pub reported: ErrorGuaranteed,
-    /// A list of spans of arguments provided that were not valid.
-    pub invalid_args: Vec<Span>,
+    /// A list of indices of arguments provided that were not valid.
+    pub invalid_args: Vec<usize>,
 }
 
 /// Decorates the result of a generic argument count mismatch