Auto merge of #77306 - lcnr:inline-ok, r=eddyb

normalize substs while inlining

fixes #68347 or more precisely, this fixes the same ICE in rust analyser as veloren is pinned to a specific nightly
and had an error with the current one.

I didn't look into creating an MVCE here as that seems fairly annoying, will spend a few minutes doing so rn. (failed)

r? `@eddyb` cc `@bjorn3`

5 files changed, 91 insertions, 7 deletions

diff --git a/compiler/rustc_mir/src/transform/inline.rs b/compiler/rustc_mir/src/transform/inline.rs
index 34aaefdcbea..796ad6c9c29 100644
--- a/compiler/rustc_mir/src/transform/inline.rs
+++ b/compiler/rustc_mir/src/transform/inline.rs
@@ -201,9 +201,13 @@ impl Inliner<'tcx> {
         let terminator = bb_data.terminator();
         if let TerminatorKind::Call { func: ref op, .. } = terminator.kind {
             if let ty::FnDef(callee_def_id, substs) = *op.ty(caller_body, self.tcx).kind() {
-                let instance = Instance::resolve(self.tcx, self.param_env, callee_def_id, substs)
-                    .ok()
-                    .flatten()?;
+                // To resolve an instance its substs have to be fully normalized, so
+                // we do this here.
+                let normalized_substs = self.tcx.normalize_erasing_regions(self.param_env, substs);
+                let instance =
+                    Instance::resolve(self.tcx, self.param_env, callee_def_id, normalized_substs)
+                        .ok()
+                        .flatten()?;
 
                 if let InstanceDef::Virtual(..) = instance.def {
                     return None;
diff --git a/compiler/rustc_trait_selection/src/traits/codegen/mod.rs b/compiler/rustc_trait_selection/src/traits/codegen/mod.rs
index dd7ea55cc10..05e6c4804ff 100644
--- a/compiler/rustc_trait_selection/src/traits/codegen/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/codegen/mod.rs
@@ -17,14 +17,17 @@ use rustc_middle::ty::{self, TyCtxt};
 /// (necessarily) resolve all nested obligations on the impl. Note
 /// that type check should guarantee to us that all nested
 /// obligations *could be* resolved if we wanted to.
+///
 /// Assumes that this is run after the entire crate has been successfully type-checked.
+/// This also expects that `trait_ref` is fully normalized.
 pub fn codegen_fulfill_obligation<'tcx>(
-    ty: TyCtxt<'tcx>,
+    tcx: TyCtxt<'tcx>,
     (param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>),
 ) -> Result<ImplSource<'tcx, ()>, ErrorReported> {
     // Remove any references to regions; this helps improve caching.
-    let trait_ref = ty.erase_regions(&trait_ref);
-
+    let trait_ref = tcx.erase_regions(&trait_ref);
+    // We expect the input to be fully normalized.
+    debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));
     debug!(
         "codegen_fulfill_obligation(trait_ref={:?}, def_id={:?})",
         (param_env, trait_ref),
@@ -33,7 +36,7 @@ pub fn codegen_fulfill_obligation<'tcx>(
 
     // Do the initial selection for the obligation. This yields the
     // shallow result we are looking for -- that is, what specific impl.
-    ty.infer_ctxt().enter(|infcx| {
+    tcx.infer_ctxt().enter(|infcx| {
         let mut selcx = SelectionContext::new(&infcx);
 
         let obligation_cause = ObligationCause::dummy();
diff --git a/src/test/ui/mir/mir-inlining/ice-issue-68347.rs b/src/test/ui/mir/mir-inlining/ice-issue-68347.rs
new file mode 100644
index 00000000000..88b80bc3333
--- /dev/null
+++ b/src/test/ui/mir/mir-inlining/ice-issue-68347.rs
@@ -0,0 +1,28 @@
+// run-pass
+// compile-flags:-Zmir-opt-level=2
+pub fn main() {
+    let _x: fn() = handle_debug_column;
+}
+
+fn handle_debug_column() {
+    let sampler = sample_columns();
+
+    let foo = || {
+        sampler.get(17);
+    };
+    foo();
+}
+
+fn sample_columns() -> impl Sampler {
+    ColumnGen {}
+}
+
+struct ColumnGen {}
+
+trait Sampler {
+    fn get(&self, index: i32);
+}
+
+impl Sampler for ColumnGen {
+    fn get(&self, _index: i32) {}
+}
diff --git a/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs b/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs
new file mode 100644
index 00000000000..4d083bf2321
--- /dev/null
+++ b/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs
@@ -0,0 +1,17 @@
+// run-pass
+// compile-flags:-Zmir-opt-level=2
+
+// Previously ICEd because we did not normalize during inlining,
+// see https://github.com/rust-lang/rust/pull/77306 for more discussion.
+
+pub fn write() {
+    create()()
+}
+
+pub fn create() -> impl FnOnce() {
+   || ()
+}
+
+fn main() {
+    write();
+}
diff --git a/src/test/ui/mir/mir-inlining/ice-issue-77306-2.rs b/src/test/ui/mir/mir-inlining/ice-issue-77306-2.rs
new file mode 100644
index 00000000000..a346d450586
--- /dev/null
+++ b/src/test/ui/mir/mir-inlining/ice-issue-77306-2.rs
@@ -0,0 +1,32 @@
+// run-pass
+// compile-flags:-Zmir-opt-level=2
+
+struct Cursor {}
+struct TokenTree {}
+
+impl Iterator for Cursor {
+    type Item = TokenTree;
+
+    fn next(&mut self) -> Option<TokenTree> {
+        None
+    }
+}
+
+fn tokenstream_probably_equal_for_proc_macro() {
+    fn break_tokens(_tree: TokenTree) -> impl Iterator<Item = TokenTree> {
+        let token_trees: Vec<TokenTree> = vec![];
+        token_trees.into_iter()
+    }
+
+    let c1 = Cursor {};
+    let c2 = Cursor {};
+
+    let mut t1 = c1.flat_map(break_tokens);
+    let mut t2 = c2.flat_map(break_tokens);
+
+    for (_t1, _t2) in t1.by_ref().zip(t2.by_ref()) {}
+}
+
+fn main() {
+    tokenstream_probably_equal_for_proc_macro();
+}