Add `proc(#const x: Type)` to enforce a constant parameter (but not polymorphic) to a procedure

src/check_expr.cpp

@@ -5991,6 +5991,15 @@ CALL_ARGUMENT_CHECKER(check_call_arguments_internal) {
 				}
 				score += s;
 
+				if (e->flags & EntityFlag_ConstInput) {
+					if (o.mode != Addressing_Constant) {
+						if (show_error) {
+							error(o.expr, "Expected a constant value for the argument '%.*s'", LIT(e->token.string));
+						}
+						err = CallArgumentError_NoneConstantParameter;
+					}
+				}
+
 				if (o.mode == Addressing_Type && is_type_typeid(e->type)) {
 					add_type_info_type(c, o.type);
 					add_type_and_value(c->info, o.expr, Addressing_Value, e->type, exact_value_typeid(o.type));
@@ -6246,6 +6255,15 @@ CALL_ARGUMENT_CHECKER(check_named_call_arguments) {
 					}
 					err = CallArgumentError_WrongTypes;
 				}
+
+				if (e->flags & EntityFlag_ConstInput) {
+					if (o->mode != Addressing_Constant) {
+						if (show_error) {
+							error(o->expr, "Expected a constant value for the argument '%.*s'", LIT(e->token.string));
+						}
+						err = CallArgumentError_NoneConstantParameter;
+					}
+				}
 			}
 			score += s;
 		}

src/check_type.cpp

@@ -1722,8 +1722,11 @@ Type *check_get_params(CheckerContext *ctx, Scope *scope, Ast *_params, bool *is
 			if (p->flags&FieldFlag_auto_cast) {
 				param->flags |= EntityFlag_AutoCast;
 			}
-			param->state = EntityState_Resolved; // NOTE(bill): This should have be resolved whilst determining it
+			if (p->flags&FieldFlag_const) {
+				param->flags |= EntityFlag_ConstInput;
+			}
 
+			param->state = EntityState_Resolved; // NOTE(bill): This should have be resolved whilst determining it
 			add_entity(ctx->checker, scope, name, param);
 			if (is_using) {
 				add_entity_use(ctx, name, param);

src/entity.cpp

@@ -46,6 +46,7 @@ enum EntityFlag {
 	EntityFlag_BitFieldValue = 1<<12,
 	EntityFlag_PolyConst     = 1<<13,
 	EntityFlag_NotExported   = 1<<14,
+	EntityFlag_ConstInput    = 1<<15,
 
 	EntityFlag_Static        = 1<<16,
 

src/parser.cpp

@@ -2998,6 +2998,7 @@ enum FieldPrefixKind {
 	FieldPrefix_Invalid = 0,
 
 	FieldPrefix_using,
+	FieldPrefix_const,
 	FieldPrefix_no_alias,
 	FieldPrefix_c_var_arg,
 	FieldPrefix_auto_cast,
@@ -3024,6 +3025,9 @@ FieldPrefixKind is_token_field_prefix(AstFile *f) {
 				return FieldPrefix_c_var_arg;
 			}
 			break;
+
+		case Token_const:
+			return FieldPrefix_const;
 		}
 		return FieldPrefix_Unknown;
 	}
@@ -3036,6 +3040,7 @@ u32 parse_field_prefixes(AstFile *f) {
 	i32 no_alias_count  = 0;
 	i32 c_vararg_count  = 0;
 	i32 auto_cast_count = 0;
+	i32 const_count     = 0;
 
 	for (;;) {
 		FieldPrefixKind kind = is_token_field_prefix(f);
@@ -3053,12 +3058,14 @@ u32 parse_field_prefixes(AstFile *f) {
 		case FieldPrefix_no_alias:  no_alias_count  += 1; advance_token(f); break;
 		case FieldPrefix_c_var_arg: c_vararg_count  += 1; advance_token(f); break;
 		case FieldPrefix_auto_cast: auto_cast_count += 1; advance_token(f); break;
+		case FieldPrefix_const:     const_count     += 1; advance_token(f); break;
 		}
 	}
 	if (using_count     > 1) syntax_error(f->curr_token, "Multiple 'using' in this field list");
 	if (no_alias_count  > 1) syntax_error(f->curr_token, "Multiple '#no_alias' in this field list");
 	if (c_vararg_count  > 1) syntax_error(f->curr_token, "Multiple '#c_vararg' in this field list");
 	if (auto_cast_count > 1) syntax_error(f->curr_token, "Multiple 'auto_cast' in this field list");
+	if (const_count     > 1) syntax_error(f->curr_token, "Multiple '#const' in this field list");
 
 
 	u32 field_flags = 0;
@@ -3066,6 +3073,7 @@ u32 parse_field_prefixes(AstFile *f) {
 	if (no_alias_count  > 0) field_flags |= FieldFlag_no_alias;
 	if (c_vararg_count  > 0) field_flags |= FieldFlag_c_vararg;
 	if (auto_cast_count > 0) field_flags |= FieldFlag_auto_cast;
+	if (const_count     > 0) field_flags |= FieldFlag_const;
 	return field_flags;
 }
 

src/parser.hpp

@@ -203,12 +203,13 @@ enum FieldFlag {
 	FieldFlag_no_alias  = 1<<2,
 	FieldFlag_c_vararg  = 1<<3,
 	FieldFlag_auto_cast = 1<<4,
+	FieldFlag_const     = 1<<5,
 
 	FieldFlag_Tags = 1<<10,
 
 	FieldFlag_Results   = 1<<16,
 
-	FieldFlag_Signature = FieldFlag_ellipsis|FieldFlag_using|FieldFlag_no_alias|FieldFlag_c_vararg|FieldFlag_auto_cast,
+	FieldFlag_Signature = FieldFlag_ellipsis|FieldFlag_using|FieldFlag_no_alias|FieldFlag_c_vararg|FieldFlag_auto_cast|FieldFlag_const,
 	FieldFlag_Struct    = FieldFlag_using|FieldFlag_Tags,
 };