From 1b2f5989e1f8a12b789e0f2e782836fd0894fbf8 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Mon, 23 Jun 2025 14:12:34 +0200
Subject: [PATCH] Assert casting bitstruct to short/char #2237

---
 releasenotes.md                               |  1 +
 src/compiler/compiler_internal.h              |  6 ++++
 src/compiler/parse_expr.c                     |  1 +
 src/compiler/sema_casts.c                     | 36 ++++++++++---------
 .../cast/implicit_widen_const_bitstruct.c3    |  9 +++++
 5 files changed, 36 insertions(+), 17 deletions(-)
 create mode 100644 test/test_suite/cast/implicit_widen_const_bitstruct.c3

diff --git a/releasenotes.md b/releasenotes.md
index 70040444e..3d4c247a2 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -61,6 +61,7 @@
 - Overload resolution fixes to inline typedef #2226.
 - `math::overflow_*` wrappers incorrectly don't allow distinct integers #2221.
 - Compiler segfault when using distinct type in attribute imported from other module #2234.
+- Assert casting bitstruct to short/char #2237
 
 ### Stdlib changes
 - Deprecate `String.is_zstr` and `String.quick_zstr` #2188.
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 2cb59ee24..27329f310 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -4094,6 +4094,12 @@ INLINE bool expr_is_const_enum(Expr *expr)
 	return expr->expr_kind == EXPR_CONST && expr->const_expr.const_kind == CONST_ENUM;
 }
 
+INLINE bool expr_is_const_number(Expr *expr)
+{
+	ASSERT(expr->resolve_status == RESOLVE_DONE);
+	return expr->expr_kind == EXPR_CONST && (expr->const_expr.const_kind == CONST_INTEGER || expr->const_expr.const_kind == CONST_FLOAT);
+}
+
 INLINE bool expr_is_const_fault(Expr *expr)
 {
 	ASSERT(expr->resolve_status == RESOLVE_DONE);
diff --git a/src/compiler/parse_expr.c b/src/compiler/parse_expr.c
index 1155b3ffc..bc9a0b569 100644
--- a/src/compiler/parse_expr.c
+++ b/src/compiler/parse_expr.c
@@ -824,6 +824,7 @@ static Expr *parse_grouping_expr(ParseContext *c, Expr *left)
 						.span = span,
 						.cast_expr.type_info = type_infoid(info),
 						.cast_expr.expr = inner};
+				RANGE_EXTEND_PREV(expr);
 			}
 			break;
 		}
diff --git a/src/compiler/sema_casts.c b/src/compiler/sema_casts.c
index 14140b37a..4ed297b84 100644
--- a/src/compiler/sema_casts.c
+++ b/src/compiler/sema_casts.c
@@ -495,22 +495,24 @@ RETRY:
 			UNREACHABLE
 		case EXPR_CONST:
 			// For constants, just check that they will fit.
-			if (type_is_integer(type))
+			switch (expr->const_expr.const_kind)
 			{
-				ASSERT(expr->const_expr.const_kind == CONST_INTEGER || expr->const_expr.const_kind == CONST_ENUM);
-				if (expr_const_will_overflow(&expr->const_expr, type_flatten(type)->type_kind))
-				{
-					return expr;
-				}
-				return NULL;
+				case CONST_ENUM:
+				case CONST_INTEGER:
+					if (expr_const_will_overflow(&expr->const_expr, type_flatten(type)->type_kind))
+					{
+						return expr;
+					}
+					return NULL;
+				case CONST_FLOAT:
+					if (!expr_const_float_fits_type(&expr->const_expr, type_flatten(type)->type_kind))
+					{
+						return expr;
+					}
+					return NULL;
+				default:
+					goto CHECK_SIZE;
 			}
-			ASSERT(type_is_float(type));
-			ASSERT(expr->const_expr.const_kind == CONST_FLOAT);
-			if (!expr_const_float_fits_type(&expr->const_expr, type_flatten(type)->type_kind))
-			{
-				return expr;
-			}
-			return NULL;
 		case EXPR_POST_UNARY:
 			expr = expr->unary_expr.expr;
 			goto RETRY;
@@ -1294,7 +1296,7 @@ static bool rule_widen_narrow(CastContext *cc, bool is_explicit, bool is_silent)
 	}
 
 	// If const, check in range.
-	if (sema_cast_const(expr) && expr_const_will_overflow(&expr->const_expr, cc->to->type_kind))
+	if (sema_cast_const(expr) && expr_is_const_number(expr) && expr_const_will_overflow(&expr->const_expr, cc->to->type_kind))
 	{
 		if (!is_silent)
 		{
@@ -1319,7 +1321,7 @@ static bool rule_widen_narrow(CastContext *cc, bool is_explicit, bool is_silent)
 		// If it's an integer that's the problem, zoom in on that one.
 		if (type_is_integer(type_flatten(problem->type))) expr = problem;
 		// Otherwise require a cast.
-		if (expr_is_const(expr))
+		if (expr_is_const_number(expr))
 		{
 			RETURN_CAST_ERROR(expr, "The value of the expression (%s) is out of range and cannot implicitly be converted to %s, but you may use a cast.",
 				expr_const_to_error_string(&expr->const_expr),
@@ -1704,7 +1706,7 @@ static void cast_int_to_int(Expr *expr, Type *type)
 	}
 
 	// Insert runtime casts on non-const.
-	if (!expr_is_const(expr))
+	if (!expr_is_const_int(expr))
 	{
 		expr_rewrite_ext_trunc(expr, type, type_is_signed(type_flatten_to_int(expr->type)));
 		return;
diff --git a/test/test_suite/cast/implicit_widen_const_bitstruct.c3 b/test/test_suite/cast/implicit_widen_const_bitstruct.c3
new file mode 100644
index 000000000..a5c1543b8
--- /dev/null
+++ b/test/test_suite/cast/implicit_widen_const_bitstruct.c3
@@ -0,0 +1,9 @@
+bitstruct Foo : ushort
+{
+	bool bar;
+}
+
+fn void main()
+{
+	ushort foo = (ushort)((Foo) {.bar}) & 1;
+}
\ No newline at end of file