refactor(traverse): speed up tests (#4538)

Closes #4537.

`oxc_traverse`'s tests to ensure code which would be undefined behavior will not compile were using `trybuild`. This is a thorough way to run these tests, but requires running a lengthy compilation each time tests run.

Implement these tests as `compile_fail` doc tests instead. This is not quite as thorough - now only testing that they don't compile, rather than also *why* they don't compile - but acceptable given the outsized cost of doing it "properly".

Cargo.lock

@@ -1847,7 +1847,6 @@ dependencies = [
  "oxc_semantic",
  "oxc_span",
  "oxc_syntax",
- "trybuild",
 ]
 
 [[package]]
@@ -2449,15 +2448,6 @@ dependencies = [
  "syn",
 ]
 
-[[package]]
-name = "serde_spanned"
-version = "0.6.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "79e674e01f999af37c49f70a6ede167a8a60b2503e56c5599532a65baa5969a0"
-dependencies = [
- "serde",
-]
-
 [[package]]
 name = "sha2"
 version = "0.10.8"
@@ -2586,15 +2576,6 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
-[[package]]
-name = "termcolor"
-version = "1.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "06794f8f6c5c898b3275aebefa6b8a1cb24cd2c6c79397ab15774837a0bc5755"
-dependencies = [
- "winapi-util",
-]
-
 [[package]]
 name = "textwrap"
 version = "0.16.1"
@@ -2713,40 +2694,6 @@ dependencies = [
  "tokio",
 ]
 
-[[package]]
-name = "toml"
-version = "0.8.14"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6f49eb2ab21d2f26bd6db7bf383edc527a7ebaee412d17af4d40fdccd442f335"
-dependencies = [
- "serde",
- "serde_spanned",
- "toml_datetime",
- "toml_edit",
-]
-
-[[package]]
-name = "toml_datetime"
-version = "0.6.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4badfd56924ae69bcc9039335b2e017639ce3f9b001c393c1b2d1ef846ce2cbf"
-dependencies = [
- "serde",
-]
-
-[[package]]
-name = "toml_edit"
-version = "0.22.14"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f21c7aaf97f1bd9ca9d4f9e73b0a6c74bd5afef56f2bc931943a6e1c37e04e38"
-dependencies = [
- "indexmap",
- "serde",
- "serde_spanned",
- "toml_datetime",
- "winnow",
-]
-
 [[package]]
 name = "tower"
 version = "0.4.13"
@@ -2864,20 +2811,6 @@ dependencies = [
  "tracing-log",
 ]
 
-[[package]]
-name = "trybuild"
-version = "1.0.98"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b55265878356bdd85c9baa15859c87de93b2bf1f33acf752040a561e4a228f62"
-dependencies = [
- "glob",
- "serde",
- "serde_derive",
- "serde_json",
- "termcolor",
- "toml",
-]
-
 [[package]]
 name = "tsify"
 version = "0.4.5"
@@ -3296,15 +3229,6 @@ version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
 
-[[package]]
-name = "winnow"
-version = "0.6.13"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "59b5e5f6c299a3c7890b876a2a587f3115162487e704907d9b6cd29473052ba1"
-dependencies = [
- "memchr",
-]
-
 [[package]]
 name = "yansi"
 version = "1.0.1"

Cargo.toml

@@ -178,7 +178,6 @@ textwrap            = "0.16.1"
 tokio               = "1.38.0"
 tower-lsp           = "0.20.0"
 tracing-subscriber  = "0.3.18"
-trybuild            = "1.0.96"
 tsify               = "0.4.5"
 unicode-id-start    = "1" # Relaxed version so the user can decide which unicode version to use.
 unicode-width       = "0.1.13"

crates/oxc_traverse/Cargo.toml

@@ -18,6 +18,8 @@ workspace = true
 
 [lib]
 test = false
+# Doctests must be enabled for this crate as they are used to run tests
+# which check the soundness of its code
 doctest = true
 
 [dependencies]
@@ -29,6 +31,3 @@ oxc_syntax    = { workspace = true }
 
 compact_str = { workspace = true }
 memoffset   = { workspace = true }
-
-[dev-dependencies]
-trybuild = { workspace = true }

crates/oxc_traverse/src/compile_fail_tests.rs

@@ -0,0 +1,81 @@
+#![cfg(doctest)]
+
+//! Tests to ensure lifetimes prevent references to escape visitor functions.
+//! If they could, it'd allow aliasing, which would be undefined behavior.
+//!
+//! These tests were originally implemented using `trybuild` crate,
+//! but it disproportionately hurt time taken to run tests.
+//! So using `compile_fail` doc tests instead.
+//! <https://github.com/oxc-project/oxc/issues/4537>
+
+/**
+```compile_fail
+use oxc_ast::ast::IdentifierReference;
+use oxc_traverse::{Ancestor, Traverse, TraverseCtx};
+
+struct Trans<'a, 'b> {
+    ancestor: Option<&'b Ancestor<'a>>,
+}
+
+impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
+    fn enter_identifier_reference(
+        &mut self,
+        _node: &mut IdentifierReference<'a>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        self.ancestor = Some(ctx.parent());
+    }
+}
+```
+*/
+const CANNOT_HOLD_ONTO_ANCESTOR: () = ();
+
+/**
+```compile_fail
+use oxc_ast::ast::IdentifierReference;
+use oxc_traverse::{ancestor::ProgramWithoutDirectives, Ancestor, Traverse, TraverseCtx};
+
+struct Trans<'a, 'b> {
+    program: Option<&'b ProgramWithoutDirectives<'a>>,
+}
+
+impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
+    fn enter_identifier_reference(
+        &mut self,
+        _node: &mut IdentifierReference<'a>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        if let Ancestor::ProgramDirectives(program) = ctx.parent() {
+            self.program = Some(program);
+        }
+    }
+}
+```
+*/
+const CANNOT_HOLD_ONTO_ANCESTOR_NODE: () = ();
+
+/**
+```compile_fail
+use oxc_ast::ast::{IdentifierReference, Statement};
+use oxc_traverse::{Ancestor, Traverse, TraverseCtx};
+
+struct Trans<'a, 'b> {
+    stmt: Option<&'b Statement<'a>>,
+}
+
+impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
+    fn enter_identifier_reference(
+        &mut self,
+        _node: &mut IdentifierReference<'a>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        if let Ancestor::ProgramDirectives(program) = ctx.parent() {
+            let body = program.body();
+            let stmt = &body[0];
+            self.stmt = Some(stmt);
+        }
+    }
+}
+```
+*/
+const CANNOT_HOLD_ONTO_AST_NODE: () = ();

crates/oxc_traverse/src/lib.rs

@@ -73,6 +73,8 @@ mod traverse;
 pub use traverse::Traverse;
 mod walk;
 
+mod compile_fail_tests;
+
 /// Traverse AST with a [`Traverse`] impl.
 ///
 /// This allows:

crates/oxc_traverse/tests/compile_fail.rs

@@ -1,5 +0,0 @@
-#[test]
-fn compile_fail() {
-    let t = trybuild::TestCases::new();
-    t.compile_fail("tests/compile_fail/*.rs");
-}

crates/oxc_traverse/tests/compile_fail/ancestor_lifetime1.rs

@@ -1,18 +0,0 @@
-use oxc_ast::ast::IdentifierReference;
-use oxc_traverse::{Ancestor, Traverse, TraverseCtx};
-
-struct Trans<'a, 'b> {
-    ancestor: Option<&'b Ancestor<'a>>,
-}
-
-impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
-    fn enter_identifier_reference(
-        &mut self,
-        _node: &mut IdentifierReference<'a>,
-        ctx: &mut TraverseCtx<'a>,
-    ) {
-        self.ancestor = Some(ctx.parent());
-    }
-}
-
-fn main() {}

crates/oxc_traverse/tests/compile_fail/ancestor_lifetime1.stderr

@@ -1,11 +0,0 @@
-error: lifetime may not live long enough
-  --> tests/compile_fail/ancestor_lifetime1.rs:14:9
-   |
-8  | impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
-   |          -- lifetime `'b` defined here
-...
-12 |         ctx: &mut TraverseCtx<'a>,
-   |              - let's call the lifetime of this reference `'1`
-13 |     ) {
-14 |         self.ancestor = Some(ctx.parent());
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment requires that `'1` must outlive `'b`

crates/oxc_traverse/tests/compile_fail/ancestor_lifetime2.rs

@@ -1,20 +0,0 @@
-use oxc_ast::ast::IdentifierReference;
-use oxc_traverse::{ancestor::ProgramWithoutDirectives, Ancestor, Traverse, TraverseCtx};
-
-struct Trans<'a, 'b> {
-    program: Option<&'b ProgramWithoutDirectives<'a>>,
-}
-
-impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
-    fn enter_identifier_reference(
-        &mut self,
-        _node: &mut IdentifierReference<'a>,
-        ctx: &mut TraverseCtx<'a>,
-    ) {
-        if let Ancestor::ProgramDirectives(program) = ctx.parent() {
-            self.program = Some(program);
-        }
-    }
-}
-
-fn main() {}

crates/oxc_traverse/tests/compile_fail/ancestor_lifetime2.stderr

@@ -1,11 +0,0 @@
-error: lifetime may not live long enough
-  --> tests/compile_fail/ancestor_lifetime2.rs:15:13
-   |
-8  | impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
-   |          -- lifetime `'b` defined here
-...
-12 |         ctx: &mut TraverseCtx<'a>,
-   |              - let's call the lifetime of this reference `'1`
-...
-15 |             self.program = Some(program);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment requires that `'1` must outlive `'b`

crates/oxc_traverse/tests/compile_fail/ancestor_lifetime3.rs

@@ -1,21 +0,0 @@
-use oxc_allocator::Vec;
-use oxc_ast::ast::{IdentifierReference, Statement};
-use oxc_traverse::{Ancestor, Traverse, TraverseCtx};
-
-struct Trans<'a, 'b> {
-    program_body: Option<&'b Vec<'a, Statement<'a>>>,
-}
-
-impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
-    fn enter_identifier_reference(
-        &mut self,
-        _node: &mut IdentifierReference<'a>,
-        ctx: &mut TraverseCtx<'a>,
-    ) {
-        if let Ancestor::ProgramDirectives(program) = ctx.parent() {
-            self.program_body = Some(program.body());
-        }
-    }
-}
-
-fn main() {}

crates/oxc_traverse/tests/compile_fail/ancestor_lifetime3.stderr

@@ -1,11 +0,0 @@
-error: lifetime may not live long enough
-  --> tests/compile_fail/ancestor_lifetime3.rs:16:13
-   |
-9  | impl<'a, 'b> Traverse<'a> for Trans<'a, 'b> {
-   |          -- lifetime `'b` defined here
-...
-13 |         ctx: &mut TraverseCtx<'a>,
-   |              - let's call the lifetime of this reference `'1`
-...
-16 |             self.program_body = Some(program.body());
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment requires that `'1` must outlive `'b`