Gate the type length limit check behind a nightly flag

compiler/rustc_middle/src/ty/instance.rs

@@ -541,7 +541,9 @@ impl<'tcx> Instance<'tcx> {
         // which means that rustc basically hangs.
         //
         // Bail out in these cases to avoid that bad user experience.
-        if !tcx.type_length_limit().value_within_limit(type_length(args)) {
+        if tcx.sess.opts.unstable_opts.enforce_type_length_limit
+            && !tcx.type_length_limit().value_within_limit(type_length(args))
+        {
             return Ok(None);
         }
 

compiler/rustc_session/src/options.rs

@@ -1709,6 +1709,8 @@ options! {
         "emit a section containing stack size metadata (default: no)"),
     emit_thin_lto: bool = (true, parse_bool, [TRACKED],
         "emit the bc module with thin LTO info (default: yes)"),
+    enforce_type_length_limit: bool = (false, parse_bool, [TRACKED],
+        "enforce the type length limit when monomorphizing instances in codegen"),
     export_executable_symbols: bool = (false, parse_bool, [TRACKED],
         "export symbols from executables, as if they were dynamic libraries"),
     external_clangrt: bool = (false, parse_bool, [UNTRACKED],

tests/ui/closures/issue-72408-nested-closures-exponential.rs

@@ -1,4 +1,4 @@
-//@ build-fail
+//@ check-pass
 
 // Closures include captured types twice in a type tree.
 //
@@ -45,7 +45,6 @@ fn main() {
 
     let f = dup(f);
     let f = dup(f);
-    //~^ ERROR reached the type-length limit
     let f = dup(f);
     let f = dup(f);
     let f = dup(f);

tests/ui/codegen/overflow-during-mono.rs

@@ -1,5 +1,5 @@
+//~ ERROR overflow evaluating the requirement `{closure@$DIR/overflow-during-mono.rs:13:41: 13:44}: Sized`
 //@ build-fail
-//@ error-pattern: reached the type-length limit while instantiating
 
 #![recursion_limit = "32"]
 

tests/ui/codegen/overflow-during-mono.stderr

@@ -1,8 +1,11 @@
-error: reached the type-length limit while instantiating `<Filter<Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, ...> as Iterator>::try_fold::<..., ..., ...>`
-  --> $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
+error[E0275]: overflow evaluating the requirement `{closure@$DIR/overflow-during-mono.rs:13:41: 13:44}: Sized`
    |
-   = help: consider adding a `#![type_length_limit="20156994"]` attribute to your crate
-   = note: the full type name has been written to '$TEST_BUILD_DIR/codegen/overflow-during-mono/overflow-during-mono.long-type.txt'
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "64"]` attribute to your crate (`overflow_during_mono`)
+   = note: required for `Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>` to implement `Iterator`
+   = note: 31 redundant requirements hidden
+   = note: required for `Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>` to implement `Iterator`
+   = note: required for `Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<Filter<std::array::IntoIter<i32, 11>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>, {closure@$DIR/overflow-during-mono.rs:13:41: 13:44}>` to implement `IntoIterator`
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0275`.

tests/ui/issues/issue-22638.rs

@@ -40,7 +40,6 @@ impl C {
     pub fn matches<F: Fn()>(&self, f: &F) {
         let &C(ref base) = self;
         base.matches(&|| {
-            //~^ ERROR reached the type-length limit
             C(base.clone()).matches(f)
         })
     }
@@ -53,6 +52,7 @@ impl D {
     pub fn matches<F: Fn()>(&self, f: &F) {
         let &D(ref a) = self;
         a.matches(f)
+        //~^ ERROR reached the recursion limit while instantiating
     }
 }
 

tests/ui/issues/issue-22638.stderr

@@ -1,13 +1,14 @@
-error: reached the type-length limit while instantiating `D::matches::<{closure@$DIR/issue-22638.rs:42:23: 42:25}>`
-  --> $DIR/issue-22638.rs:42:9
+error: reached the recursion limit while instantiating `A::matches::<{closure@$DIR/issue-22638.rs:42:23: 42:25}>`
+  --> $DIR/issue-22638.rs:54:9
    |
-LL | /         base.matches(&|| {
-LL | |
-LL | |             C(base.clone()).matches(f)
-LL | |         })
-   | |__________^
+LL |         a.matches(f)
+   |         ^^^^^^^^^^^^
    |
-   = help: consider adding a `#![type_length_limit="30408681"]` attribute to your crate
+note: `A::matches` defined here
+  --> $DIR/issue-22638.rs:13:5
+   |
+LL |     pub fn matches<F: Fn()>(&self, f: &F) {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 1 previous error
 

tests/ui/issues/issue-37311-type-length-limit/issue-37311.rs

@@ -15,7 +15,7 @@ impl<T> Foo for T {
     #[allow(unconditional_recursion)]
     fn recurse(&self) {
         (self, self).recurse();
-        //~^ ERROR reached the type-length limit
+        //~^ ERROR reached the recursion limit while instantiating
     }
 }
 

tests/ui/issues/issue-37311-type-length-limit/issue-37311.stderr

@@ -1,10 +1,14 @@
-error: reached the type-length limit while instantiating `<(&(&(..., ...), ...), ...) as Foo>::recurse`
+error: reached the recursion limit while instantiating `<(&(&(..., ...), ...), ...) as Foo>::recurse`
   --> $DIR/issue-37311.rs:17:9
    |
 LL |         (self, self).recurse();
    |         ^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: consider adding a `#![type_length_limit="33554429"]` attribute to your crate
+note: `<T as Foo>::recurse` defined here
+  --> $DIR/issue-37311.rs:16:5
+   |
+LL |     fn recurse(&self) {
+   |     ^^^^^^^^^^^^^^^^^
    = note: the full type name has been written to '$TEST_BUILD_DIR/issues/issue-37311-type-length-limit/issue-37311/issue-37311.long-type.txt'
 
 error: aborting due to 1 previous error

tests/ui/iterators/issue-58952-filter-type-length.rs

@@ -1,5 +1,4 @@
-//@ build-fail
-//@ error-pattern: reached the type-length limit while instantiating
+//@ build-pass
 
 //! This snippet causes the type length to blowup exponentially,
 //! so check that we don't accidentally exceed the type length limit.

tests/ui/recursion/issue-83150.rs

@@ -1,3 +1,4 @@
+//~ ERROR overflow evaluating the requirement `Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>: Iterator`
 //@ build-fail
 //@ compile-flags: -Copt-level=0
 //@ normalize-stderr-test: "long-type-\d+" -> "long-type-hash"
@@ -11,5 +12,4 @@ fn main() {
 fn func<T: Iterator<Item = u8>>(iter: &mut T) {
     //~^ WARN function cannot return without recursing
     func(&mut iter.map(|x| x + 1))
-    //~^ ERROR reached the type-length limit
 }

tests/ui/recursion/issue-83150.stderr

@@ -1,5 +1,5 @@
 warning: function cannot return without recursing
-  --> $DIR/issue-83150.rs:11:1
+  --> $DIR/issue-83150.rs:12:1
    |
 LL | fn func<T: Iterator<Item = u8>>(iter: &mut T) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot return without recursing
@@ -10,14 +10,13 @@ LL |     func(&mut iter.map(|x| x + 1))
    = help: a `loop` may express intention better if this is on purpose
    = note: `#[warn(unconditional_recursion)]` on by default
 
-error: reached the type-length limit while instantiating `<&mut Map<&mut Map<&mut ..., ...>, ...> as Iterator>::map::<..., ...>`
-  --> $DIR/issue-83150.rs:13:15
+error[E0275]: overflow evaluating the requirement `Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>: Iterator`
    |
-LL |     func(&mut iter.map(|x| x + 1))
-   |               ^^^^^^^^^^^^^^^^^^^
-   |
-   = help: consider adding a `#![type_length_limit="23068663"]` attribute to your crate
-   = note: the full type name has been written to '$TEST_BUILD_DIR/recursion/issue-83150/issue-83150.long-type.txt'
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_83150`)
+   = note: required for `&mut Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>` to implement `Iterator`
+   = note: 65 redundant requirements hidden
+   = note: required for `&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut Map<&mut std::ops::Range<u8>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>, {closure@$DIR/issue-83150.rs:14:24: 14:27}>` to implement `Iterator`
 
 error: aborting due to 1 previous error; 1 warning emitted
 
+For more information about this error, try `rustc --explain E0275`.

tests/ui/traits/issue-91949-hangs-on-recursion.rs

@@ -1,3 +1,4 @@
+//~ ERROR overflow evaluating the requirement `<std::iter::Empty<()> as Iterator>::Item == ()`
 //@ build-fail
 //@ compile-flags: -Zinline-mir=no
 
@@ -23,7 +24,6 @@ where
     T: Iterator<Item = ()>,
 {
     recurse(IteratorOfWrapped(elements).map(|t| t.0))
-    //~^ ERROR reached the type-length limit
 }
 
 fn main() {