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`

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) {}
+}

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();
+}

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();
+}