Treat `*x` as an unary operator to improve error messages for common C-programmer mistakes

src/check_expr.cpp

@@ -1800,6 +1800,19 @@ gb_internal bool check_unary_op(CheckerContext *c, Operand *o, Token op) {
 		}
 		break;
 
+	case Token_Mul:
+		{
+			ERROR_BLOCK();
+			error(op, "Operator '%.*s' is not a valid unary operator in Odin", LIT(op.string));
+			if (is_type_pointer(o->type)) {
+				str = expr_to_string(o->expr);
+				error_line("\tSuggestion: Did you mean '%s^'?\n", str);
+			} else if (is_type_multi_pointer(o->type)) {
+				str = expr_to_string(o->expr);
+				error_line("\tSuggestion: The value is a multi-pointer, did you mean '%s[0]'?\n", str);
+			}
+		}
+		break;
 	default:
 		error(op, "Unknown operator '%.*s'", LIT(op.string));
 		return false;

src/check_type.cpp

@@ -3375,7 +3375,9 @@ gb_internal Type *check_type_expr(CheckerContext *ctx, Ast *e, Type *named_type)
 		type = t_invalid;
 
 
-		// NOTE(bill): Check for common mistakes from C programmers e.g. T[] and T[N]
+		// NOTE(bill): Check for common mistakes from C programmers
+		// e.g. T[] and T[N]
+		// e.g. *T
 		Ast *node = unparen_expr(e);
 		if (node && node->kind == Ast_IndexExpr) {
 			gbString index_str = nullptr;
@@ -3395,6 +3397,18 @@ gb_internal Type *check_type_expr(CheckerContext *ctx, Ast *e, Type *named_type)
 				Ast *pseudo_array_expr = ast_array_type(e->file(), ast_token(node->IndexExpr.expr), node->IndexExpr.index, node->IndexExpr.expr);
 				check_array_type_internal(ctx, pseudo_array_expr, &type, nullptr);
 			}
+		} else if (node && node->kind == Ast_UnaryExpr && node->UnaryExpr.op.kind == Token_Mul) {
+			gbString type_str = expr_to_string(node->UnaryExpr.expr);
+			defer (gb_string_free(type_str));
+
+			error_line("\tSuggestion: Did you mean '^%s'?\n", type_str);
+			end_error_block();
+
+			// NOTE(bill): Minimize error propagation of bad array syntax by treating this like a type
+			if (node->UnaryExpr.expr != nullptr) {
+				Ast *pseudo_pointer_expr = ast_pointer_type(e->file(), ast_token(node->UnaryExpr.expr), node->UnaryExpr.expr);
+				return check_type_expr(ctx, pseudo_pointer_expr, named_type);
+			}
 		} else {
 			end_error_block();
 		}

src/parser.cpp

@@ -2541,6 +2541,9 @@ gb_internal Ast *parse_operand(AstFile *f, bool lhs) {
 		return ast_pointer_type(f, token, elem);
 	} break;
 
+	case Token_Mul:
+		return parse_unary_expr(f, true);
+
 	case Token_OpenBracket: {
 		Token token = expect_token(f, Token_OpenBracket);
 		Ast *count_expr = nullptr;
@@ -3274,7 +3277,9 @@ gb_internal Ast *parse_unary_expr(AstFile *f, bool lhs) {
 	case Token_Sub:
 	case Token_Xor:
 	case Token_And:
-	case Token_Not: {
+	case Token_Not:
+	case Token_Mul: // Used for error handling when people do C-like things
+	{
 		Token token = advance_token(f);
 		Ast *expr = parse_unary_expr(f, lhs);
 		return ast_unary_expr(f, token, expr);