fuzz: Add ast fuzzer

fuzz/Cargo.toml

@@ -8,6 +8,7 @@ edition = "2018"
 cargo-fuzz = true
 
 [dependencies]
+anyhow = "1.0.78"
 arbitrary = { version = "1.3.2", features = ["derive"] }
 libfuzzer-sys = "0.4"
 rhai = { path = "..", features = ["fuzz", "decimal", "metadata", "debugging"] }
@@ -24,3 +25,9 @@ name = "scripting"
 path = "fuzz_targets/scripting.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "ast"
+path = "fuzz_targets/ast.rs"
+test = false
+doc = false

fuzz/fuzz_targets/ast.rs

@@ -0,0 +1,56 @@
+#![no_main]
+use rhai::{Engine, OptimizationLevel};
+
+use anyhow::Result;
+use arbitrary::Arbitrary;
+use libfuzzer_sys::fuzz_target;
+use std::{hint::black_box};
+
+#[derive(Debug, Clone, Arbitrary)]
+struct Ctx<'a> {
+    script: &'a str,
+    optimization_level: OptimizationLevel,
+}
+
+fn fuzz(ctx: Ctx) -> Result<()> {
+    let mut engine = Engine::new();
+
+    engine.set_max_string_size(1000);
+    engine.set_max_array_size(500);
+    engine.set_max_map_size(500);
+    engine.set_max_variables(1000);
+    engine.set_max_modules(1000);
+    engine.set_max_call_levels(10);
+    engine.set_max_expr_depths(50, 5);
+    engine.set_optimization_level(ctx.optimization_level);
+
+    // Don't actually print to stdout, but also don't optimise
+    // printing code away.
+    engine.on_debug(|x, src, pos| _ = black_box((x, src, pos)));
+    engine.on_print(move |s| {
+        _ = black_box(s);
+    });
+
+    // Limit the length of scripts.
+    let script = ctx.script.chars().take(32 * 1024).collect::<String>();
+
+    let ast = engine.compile(script)?;
+    _ = black_box(format!("{ast:?}"));
+    _ = black_box(ast.iter_functions().count());
+    _ = black_box(ast.iter_literal_variables(true, true).count());
+    _ = black_box(ast.walk(&mut |_| true));
+
+    let mut function_only_ast = ast.clone_functions_only();
+    assert!(function_only_ast.clear_functions().iter_functions().count() == 0);
+
+    let function_only_ast = ast.clone_functions_only_filtered(|_, _, _, _, _| true);
+    _ = black_box(function_only_ast.merge(&ast));
+
+    Ok(())
+}
+
+fuzz_target!(|ctx: Ctx| {
+    if let Err(e) = fuzz(ctx) {
+        _ = black_box(format!("{e}"));
+    }
+});