Auto merge of #109753 - compiler-errors:replenish-region-constraints, r=aliemjay

Clone region var origins instead of taking them in borrowck

Fixes an issue with the new solver where reporting a borrow-checker error ICEs because it calls `InferCtxt::evaluate_obligation`.

This also removes a handful of unnecessary `tcx.infer_ctxt().build()` calls that are only there to mitigate this same exact issue, but with the old solver.

Fixes compiler-errors/next-solver-hir-issues#12.

----

This implements `@aliemjay's` solution where we just don't *take* the region constraints, but clone them. This potentially makes it easier to write a bug about taking region constraints twice or never at all, but again, not many folks are touching this code.

2 files changed, 23 insertions, 0 deletions

diff --git a/tests/ui/traits/new-solver/borrowck-error.rs b/tests/ui/traits/new-solver/borrowck-error.rs
new file mode 100644
index 00000000000..4787a2c7e11
--- /dev/null
+++ b/tests/ui/traits/new-solver/borrowck-error.rs
@@ -0,0 +1,11 @@
+// compile-flags: -Ztrait-solver=next
+
+use std::collections::HashMap;
+
+fn foo() -> &'static HashMap<i32, i32>
+{
+    &HashMap::new()
+    //~^ ERROR cannot return reference to temporary value
+}
+
+fn main() {}
diff --git a/tests/ui/traits/new-solver/borrowck-error.stderr b/tests/ui/traits/new-solver/borrowck-error.stderr
new file mode 100644
index 00000000000..a7d8201747a
--- /dev/null
+++ b/tests/ui/traits/new-solver/borrowck-error.stderr
@@ -0,0 +1,12 @@
+error[E0515]: cannot return reference to temporary value
+  --> $DIR/borrowck-error.rs:7:5
+   |
+LL |     &HashMap::new()
+   |     ^--------------
+   |     ||
+   |     |temporary value created here
+   |     returns a reference to data owned by the current function
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0515`.