Report prescan errors on their source lines

tests/read_data.c

@@ -8,6 +8,7 @@
  * TODO.md section 6.
  */
 
+#include <stdio.h>
 #include <string.h>
 
 #include <akbasic/error.h>
@@ -174,6 +175,34 @@ static void test_colon_ends_data(void)
     harness_stop();
 }
 
+/** @brief DATA overflow reports the line where the item limit was crossed. */
+static void test_data_prescan_error_line(void)
+{
+    char source[4096] = "";
+    size_t used = 0;
+    int line = 0;
+    int item = 0;
+
+    for ( line = 1; line <= 34; line++ ) {
+	used += (size_t)snprintf(source + used, sizeof(source) - used, "%d DATA ", line);
+	for ( item = 0; item < 15; item++ ) {
+	    used += (size_t)snprintf(source + used, sizeof(source) - used,
+				      "%s1", (item == 0 ? "" : ","));
+	}
+	used += (size_t)snprintf(source + used, sizeof(source) - used, "\n");
+    }
+	used += (size_t)snprintf(source + used, sizeof(source) - used, "100 DATA 1,1\n");
+	(void)snprintf(source + used, sizeof(source) - used, "101 DATA 1\n200 PRINT 1\n");
+
+    TEST_REQUIRE_OK(harness_start(NULL));
+    TEST_REQUIRE_OK(akbasic_runtime_load(&HARNESS_RUNTIME, source));
+    TEST_REQUIRE_OK(akbasic_runtime_start(&HARNESS_RUNTIME, AKBASIC_MODE_RUN));
+	TEST_REQUIRE(strstr(HARNESS_OUTPUT, "? 101 : PARSE ERROR") != NULL,
+		 "DATA overflow should report its source line, got \"%s\"",
+		 HARNESS_OUTPUT);
+    harness_stop();
+}
+
 /** @brief A float item fills a float variable with its fractional part intact. */
 static void test_float_items(void)
 {
@@ -227,6 +256,7 @@ int main(void)
     test_type_mismatch();
     test_quoted_items();
     test_colon_ends_data();
+	test_data_prescan_error_line();
     test_float_items();
     test_negative_items();
     return akbasic_test_failures;