Support generics in check for valid types in arithmetic expressions

When we check for valid types we need to be sure to call destructure which
will extract out any generics so that we are checking the actual concrete
type that is being used here.

Fixes #1383

2 files changed, 17 insertions, 5 deletions

diff --git a/gcc/rust/typecheck/rust-hir-type-check-expr.h b/gcc/rust/typecheck/rust-hir-type-check-expr.h
index a5f0a84..df07cb3 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-expr.h
+++ b/gcc/rust/typecheck/rust-hir-type-check-expr.h
@@ -1060,9 +1060,11 @@ private:
 			 Location expr_locus);
 
   bool
-  validate_arithmetic_type (TyTy::BaseType *type,
+  validate_arithmetic_type (const TyTy::BaseType *tyty,
 			    HIR::ArithmeticOrLogicalExpr::ExprType expr_type)
   {
+    const TyTy::BaseType *type = tyty->destructure ();
+
     // https://doc.rust-lang.org/reference/expressions/operator-expr.html#arithmetic-and-logical-binary-operators
     // this will change later when traits are added
     switch (expr_type)
@@ -1078,10 +1080,10 @@ private:
 	       || (type->get_kind () == TyTy::TypeKind::USIZE)
 	       || (type->get_kind () == TyTy::TypeKind::ISIZE)
 	       || (type->get_kind () == TyTy::TypeKind::INFER
-		   && (((TyTy::InferType *) type)->get_infer_kind ()
+		   && (((const TyTy::InferType *) type)->get_infer_kind ()
 		       == TyTy::InferType::INTEGRAL))
 	       || (type->get_kind () == TyTy::TypeKind::INFER
-		   && (((TyTy::InferType *) type)->get_infer_kind ()
+		   && (((const TyTy::InferType *) type)->get_infer_kind ()
 		       == TyTy::InferType::FLOAT));
 
 	// integers or bools
@@ -1094,7 +1096,7 @@ private:
 	       || (type->get_kind () == TyTy::TypeKind::ISIZE)
 	       || (type->get_kind () == TyTy::TypeKind::BOOL)
 	       || (type->get_kind () == TyTy::TypeKind::INFER
-		   && (((TyTy::InferType *) type)->get_infer_kind ()
+		   && (((const TyTy::InferType *) type)->get_infer_kind ()
 		       == TyTy::InferType::INTEGRAL));
 
 	// integers only
@@ -1105,10 +1107,12 @@ private:
 	       || (type->get_kind () == TyTy::TypeKind::USIZE)
 	       || (type->get_kind () == TyTy::TypeKind::ISIZE)
 	       || (type->get_kind () == TyTy::TypeKind::INFER
-		   && (((TyTy::InferType *) type)->get_infer_kind ()
+		   && (((const TyTy::InferType *) type)->get_infer_kind ()
 		       == TyTy::InferType::INTEGRAL));
       }
+
     gcc_unreachable ();
+    return false;
   }
 
   /* The return value of TypeCheckExpr::Resolve */
diff --git a/gcc/testsuite/rust/compile/issue-1383.rs b/gcc/testsuite/rust/compile/issue-1383.rs
new file mode 100644
index 0000000..cca12e8
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-1383.rs
@@ -0,0 +1,8 @@
+pub fn generic_function<X>(a: X) -> X {
+    a
+}
+
+fn main() -> i32 {
+    let a = generic_function(123);
+    a - 123
+}