gccrs: Fix bad cast as a char

In rust cast to char is allowed only from u8 type.
This patch handles fix the case when the type is infered from an integer value,
allowing only the u8 case'

Fixes #2027

gcc/rust/ChangeLog:

	* typecheck/rust-casts.cc (TypeCastRules::cast_rules):
	case INTEGRAL handles TypeKind::CHAR

gcc/testsuite/ChangeLog:

	* rust/compile/cast5.rs: New test.

Signed-off-by: Emanuele Micheletti <micheletti.emanuele@hotmail.com>

2 files changed, 27 insertions, 2 deletions

diff --git a/gcc/rust/typecheck/rust-casts.cc b/gcc/rust/typecheck/rust-casts.cc
index 31449a6..4134a7d 100644
--- a/gcc/rust/typecheck/rust-casts.cc
+++ b/gcc/rust/typecheck/rust-casts.cc
@@ -64,7 +64,6 @@ TypeCastRules::cast_rules ()
 
   rust_debug ("cast_rules from={%s} to={%s}", from_type->debug_str ().c_str (),
 	      to.get_ty ()->debug_str ().c_str ());
-
   switch (from_type->get_kind ())
     {
       case TyTy::TypeKind::INFER: {
@@ -79,7 +78,21 @@ TypeCastRules::cast_rules ()
 	  case TyTy::InferType::InferTypeKind::INTEGRAL:
 	    switch (to.get_ty ()->get_kind ())
 	      {
-	      case TyTy::TypeKind::CHAR:
+		case TyTy::TypeKind::CHAR: {
+		  // only u8 and char
+		  bool was_uint
+		    = from.get_ty ()->get_kind () == TyTy::TypeKind::UINT;
+		  bool was_u8
+		    = was_uint
+		      && (static_cast<TyTy::UintType *> (from.get_ty ())
+			    ->get_uint_kind ()
+			  == TyTy::UintType::UintKind::U8);
+		  if (was_u8)
+		    return TypeCoercionRules::CoercionResult{
+		      {}, to.get_ty ()->clone ()};
+		}
+		break;
+
 	      case TyTy::TypeKind::USIZE:
 	      case TyTy::TypeKind::ISIZE:
 	      case TyTy::TypeKind::UINT:
diff --git a/gcc/testsuite/rust/compile/cast5.rs b/gcc/testsuite/rust/compile/cast5.rs
new file mode 100644
index 0000000..ecc10c1
--- /dev/null
+++ b/gcc/testsuite/rust/compile/cast5.rs
@@ -0,0 +1,12 @@
+fn main() {
+    const A: char = 0x1F888 as char;
+    // { dg-error "invalid cast .<integer>. to .char." "" { target *-*-* } .-1 }
+    const B: char = 129160 as char;
+    // { dg-error "invalid cast .<integer>. to .char." "" { target *-*-* } .-1 }
+    const C: i32 = 42;
+    const D: char = C as char;
+    // { dg-error "invalid cast .i32. to .char." "" { target *-*-* } .-1 }
+    const E: char = '\u{01F888}';
+    const F: u8 = 42; 
+    const G: char= F as char;
+}