[gcc/devel/rust/master] The number of required substituions is offset from the already substituted

[gcc/devel/rust/master] The number of required substituions is offset from the already substituted

[Thomas Schwinge]

https://gcc.gnu.org/g:b538aa91056a10b31c54580316c49c764f884d67

commit b538aa91056a10b31c54580316c49c764f884d67
Author: Philip Herron <philip.herron@embecosm.com>
Date:   Thu Oct 21 18:27:37 2021 +0100

    The number of required substituions is offset from the already substituted
    
    When doing HIR::GenericArgs substitutions we must offset from the already
    partially substituted arguments.

Diff:
---
 gcc/rust/typecheck/rust-tyty.cc | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index f08d8cb200d..a361653bc0c 100644
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -357,7 +357,9 @@ SubstitutionRef::get_mappings_from_generic_args (HIR::GenericArgs &args)
       return SubstitutionArgumentMappings::error ();
     }
 
-  if (args.get_type_args ().size () > substitutions.size ())
+  // for inherited arguments
+  size_t offs = used_arguments.size ();
+  if (args.get_type_args ().size () + offs > substitutions.size ())
     {
       RichLocation r (args.get_locus ());
       r.add_range (substitutions.front ().get_param_locus ());
@@ -369,7 +371,7 @@ SubstitutionRef::get_mappings_from_generic_args (HIR::GenericArgs &args)
       return SubstitutionArgumentMappings::error ();
     }
 
-  if (args.get_type_args ().size () < min_required_substitutions ())
+  if (args.get_type_args ().size () + offs < min_required_substitutions ())
     {
       RichLocation r (args.get_locus ());
       r.add_range (substitutions.front ().get_param_locus ());
@@ -381,9 +383,6 @@ SubstitutionRef::get_mappings_from_generic_args (HIR::GenericArgs &args)
       return SubstitutionArgumentMappings::error ();
     }
 
-  // for inherited arguments
-  size_t offs = used_arguments.size ();
-
   std::vector<SubstitutionArg> mappings;
   for (auto &arg : args.get_type_args ())
     {