Merge #1013

1013: Fuzz reparsing and fix found bugs r=matklad a=pcpthm

Add fuzz test for reparsing which:
- Checks reparsing doesn't panic and validate result syntax tree.
- Checks that incremental reparsing produces the same syntax tree as full reparse.
- Check for that errors are the same as full reparsing is disabled because errors are less important than syntax tree and produce failures which I couldn't figure out how to fix immediately (FIXME comment).

I guess the current input generation is inefficient but still found several bugs:
- Arithmetic overflow (negative result on an unsigned type). I changed the signature of `SyntaxError::add_offset` to solve this problem.
- When reparsing a leaf, the token of the leaf can be joined to the next characters. Such case was not considered.
- UNDERSCORE token was not produced when text length is exactly 1 (not a reparsing bug).
- When reparsing a block, *inner* curly braces should be balanced. i.e. `{}{}` is invalid.
- Effects of deleting newlines were not considered.

Co-authored-by: pcpthm <[email protected]>

1 files changed, 11 insertions, 2 deletions

diff --git a/crates/ra_syntax/tests/test.rs b/crates/ra_syntax/tests/test.rs
index 458740c13..537b01368 100644
--- a/crates/ra_syntax/tests/test.rs
+++ b/crates/ra_syntax/tests/test.rs
@@ -8,7 +8,7 @@ use std::{
 };
 
 use test_utils::{project_dir, dir_tests, read_text, collect_tests};
-use ra_syntax::{SourceFile, AstNode, check_fuzz_invariants};
+use ra_syntax::{SourceFile, AstNode, fuzz};
 
 #[test]
 fn lexer_tests() {
@@ -47,7 +47,16 @@ fn parser_tests() {
 #[test]
 fn parser_fuzz_tests() {
     for (_, text) in collect_tests(&test_data_dir(), &["parser/fuzz-failures"]) {
-        check_fuzz_invariants(&text)
+        fuzz::check_parser(&text)
+    }
+}
+
+#[test]
+fn reparse_fuzz_tests() {
+    for (_, text) in collect_tests(&test_data_dir(), &["reparse/fuzz-failures"]) {
+        let check = fuzz::CheckReparse::from_data(text.as_bytes()).unwrap();
+        println!("{:?}", check);
+        check.run();
     }
 }