Rollup merge of #111880 - compiler-errors:pointer-like-param-env, r=jackh726

Don't ICE when computing PointerLike trait when region vars are in param-env

Fixes #111877

Author: matthiaskrgr

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -177,14 +177,18 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
             return Err(NoSolution);
         }
 
-        if goal.predicate.self_ty().has_non_region_infer() {
+        // The regions of a type don't affect the size of the type
+        let tcx = ecx.tcx();
+        // We should erase regions from both the param-env and type, since both
+        // may have infer regions. Specifically, after canonicalizing and instantiating,
+        // early bound regions turn into region vars in both the new and old solver.
+        let key = tcx.erase_regions(goal.param_env.and(goal.predicate.self_ty()));
+        // But if there are inference variables, we have to wait until it's resolved.
+        if key.has_non_region_infer() {
             return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
         }
 
-        let tcx = ecx.tcx();
-        let self_ty = tcx.erase_regions(goal.predicate.self_ty());
-
-        if let Ok(layout) = tcx.layout_of(goal.param_env.and(self_ty))
+        if let Ok(layout) = tcx.layout_of(key)
             && layout.layout.is_pointer_like(&tcx.data_layout)
         {
             // FIXME: We could make this faster by making a no-constraints response

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -967,16 +967,18 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     ) {
         // The regions of a type don't affect the size of the type
         let tcx = self.tcx();
-        let self_ty =
-            tcx.erase_regions(tcx.erase_late_bound_regions(obligation.predicate.self_ty()));
-
+        let self_ty = tcx.erase_late_bound_regions(obligation.predicate.self_ty());
+        // We should erase regions from both the param-env and type, since both
+        // may have infer regions. Specifically, after canonicalizing and instantiating,
+        // early bound regions turn into region vars in both the new and old solver.
+        let key = tcx.erase_regions(obligation.param_env.and(self_ty));
         // But if there are inference variables, we have to wait until it's resolved.
-        if self_ty.has_non_region_infer() {
+        if key.has_non_region_infer() {
             candidates.ambiguous = true;
             return;
         }
 
-        if let Ok(layout) = tcx.layout_of(obligation.param_env.and(self_ty))
+        if let Ok(layout) = tcx.layout_of(key)
             && layout.layout.is_pointer_like(&tcx.data_layout)
         {
             candidates.vec.push(BuiltinCandidate { has_nested: false });

tests/ui/dyn-star/param-env-infer.current.stderr

@@ -0,0 +1,18 @@
+warning: the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/param-env-infer.rs:5:12
+   |
+LL | #![feature(dyn_star, pointer_like_trait)]
+   |            ^^^^^^^^
+   |
+   = note: see issue #102425 <https://github.com/rust-lang/rust/issues/102425> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0282]: type annotations needed
+  --> $DIR/param-env-infer.rs:12:10
+   |
+LL |     t as _
+   |          ^ cannot infer type
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0282`.

tests/ui/dyn-star/param-env-infer.next.stderr

@@ -0,0 +1,18 @@
+warning: the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/param-env-infer.rs:5:12
+   |
+LL | #![feature(dyn_star, pointer_like_trait)]
+   |            ^^^^^^^^
+   |
+   = note: see issue #102425 <https://github.com/rust-lang/rust/issues/102425> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0282]: type annotations needed
+  --> $DIR/param-env-infer.rs:12:10
+   |
+LL |     t as _
+   |          ^ cannot infer type
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0282`.

tests/ui/dyn-star/param-env-infer.rs

@@ -0,0 +1,16 @@
+// revisions: current next
+//[next] compile-flags: -Ztrait-solver=next
+// incremental
+
+#![feature(dyn_star, pointer_like_trait)]
+//~^ WARN the feature `dyn_star` is incomplete and may not be safe to use and/or cause compiler crashes
+
+use std::fmt::Debug;
+use std::marker::PointerLike;
+
+fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
+    t as _
+    //~^ ERROR type annotations needed
+}
+
+fn main() {}