add test of the new attr and fix the breaking test

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

compiler/rustc_expand/src/expand.rs

@@ -2027,7 +2027,7 @@ impl<'feat> ExpansionConfig<'feat> {
             crate_name,
             features: None,
             recursion_limit: Limit::new(1024),
-            expansion_growth_limit: Limit::new(1500),
+            expansion_growth_limit: Limit::new(6000),
             trace_mac: false,
             should_test: false,
             span_debug: false,

compiler/rustc_middle/src/middle/limits.rs

@@ -42,7 +42,7 @@ pub fn get_recursion_limit(krate_attrs: &[Attribute], sess: &Session) -> Limit {
 }
 
 pub fn get_expansion_growth_limit(krate_attrs: &[Attribute], sess: &Session) -> Limit {
-    get_limit(krate_attrs, sess, sym::expansion_growth_limit, 1500)
+    get_limit(krate_attrs, sess, sym::expansion_growth_limit, 6000)
 }
 
 fn get_limit(krate_attrs: &[Attribute], sess: &Session, name: Symbol, default: usize) -> Limit {

compiler/rustc_session/src/session.rs

@@ -128,7 +128,10 @@ pub struct Limits {
     pub move_size_limit: Limit,
     /// The maximum length of types during monomorphization.
     pub type_length_limit: Limit,
-    /// FIXME(vincenzopalazzo) add docs
+    /// The maximum blocks a const expression can evaluate.
+    pub const_eval_limit: Limit,
+    /// The maximum tokens limit for potentially infinitely resolving
+    /// a macros that add infinite tokens inside the buffer.
     pub expansion_growth_limit: Limit,
 }
 

tests/ui/limits/issue-95698.rs

@@ -0,0 +1,25 @@
+// check-fail
+
+/// issue #95698
+macro_rules! from_cow_impls {
+    ($( $from: ty ),+ $(,)? ) => {
+        // recursion call
+        from_cow_impls!(
+            $( $from, Cow::from ),+
+        );
+        //~^^^ ERROR expansion grow limit reached while expanding `from_cow_impls!`
+    };
+
+    ($( $from: ty, $normalizer: expr ),+ $(,)? ) => {
+        $( impl<'a> From<$from> for LhsValue<'a> {
+            fn from(val: $from) -> Self {
+                LhsValue::Bytes($normalizer(val))
+            }
+        } )+
+    };
+}
+
+from_cow_impls!(
+    &'a [u8], /*callback,*/
+    Vec<u8>, /*callback,*/
+);

tests/ui/limits/issue-95698.stderr

@@ -0,0 +1,19 @@
+error: expansion grow limit reached while expanding `from_cow_impls!`
+  --> $DIR/issue-95698.rs:7:9
+   |
+LL | /         from_cow_impls!(
+LL | |             $( $from, Cow::from ),+
+LL | |         );
+   | |_________^
+...
+LL | / from_cow_impls!(
+LL | |     &'a [u8], /*callback,*/
+LL | |     Vec<u8>, /*callback,*/
+LL | | );
+   | |_- in this macro invocation
+   |
+   = help: consider increasing the expansion grow limit by adding a `#![expansion_growth_limit = "12000"]` attribute to your crate (`issue_95698`)
+   = note: this error originates in the macro `from_cow_impls` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+

tests/ui/mir/issue-29227.rs

@@ -1,3 +1,4 @@
+#![expansion_growth_limit = "16000"]
 // run-pass
 // ignore-tidy-linelength