From a4707a4f3b38bd6aae7a452300ef5c65da19e524 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 8 May 2025 19:43:33 +0000
Subject: [PATCH] Do not ICE when reassigning in GatherLocalsVisitor on the bad
path
---
.../rustc_hir_typeck/src/gather_locals.rs | 14 +++++++++++--
tests/ui/typeck/gather-locals-twice.rs | 7 +++++++
tests/ui/typeck/gather-locals-twice.stderr | 20 +++++++++++++++++++
3 files changed, 39 insertions(+), 2 deletions(-)
create mode 100644 tests/ui/typeck/gather-locals-twice.rs
create mode 100644 tests/ui/typeck/gather-locals-twice.stderr
diff --git a/compiler/rustc_hir_typeck/src/gather_locals.rs b/compiler/rustc_hir_typeck/src/gather_locals.rs
index a8bbc89dbded5..956671fc66ed2 100644
--- a/compiler/rustc_hir_typeck/src/gather_locals.rs
+++ b/compiler/rustc_hir_typeck/src/gather_locals.rs
@@ -105,16 +105,26 @@ impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
}
fn assign(&mut self, span: Span, nid: HirId, ty_opt: Option<Ty<'tcx>>) -> Ty<'tcx> {
+ // We evaluate expressions twice occasionally in diagnostics for better
+ // type information or because it needs type information out-of-order.
+ // In order to not ICE and not lead to knock-on ambiguity errors, if we
+ // try to re-assign a type to a local, then just take out the previous
+ // type and delay a bug.
+ if let Some(&local) = self.fcx.locals.borrow_mut().get(&nid) {
+ self.fcx.dcx().span_delayed_bug(span, "evaluated expression more than once");
+ return local;
+ }
+
match ty_opt {
None => {
// Infer the variable's type.
let var_ty = self.fcx.next_ty_var(span);
- assert_eq!(self.fcx.locals.borrow_mut().insert(nid, var_ty), None);
+ self.fcx.locals.borrow_mut().insert(nid, var_ty);
var_ty
}
Some(typ) => {
// Take type that the user specified.
- assert_eq!(self.fcx.locals.borrow_mut().insert(nid, typ), None);
+ self.fcx.locals.borrow_mut().insert(nid, typ);
typ
}
}
diff --git a/tests/ui/typeck/gather-locals-twice.rs b/tests/ui/typeck/gather-locals-twice.rs
new file mode 100644
index 0000000000000..e9351146f4564
--- /dev/null
+++ b/tests/ui/typeck/gather-locals-twice.rs
@@ -0,0 +1,7 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/140785>.
+
+fn main() {
+ () += { let x; };
+ //~^ ERROR binary assignment operation `+=` cannot be applied to type `()`
+ //~| ERROR invalid left-hand side of assignment
+}
diff --git a/tests/ui/typeck/gather-locals-twice.stderr b/tests/ui/typeck/gather-locals-twice.stderr
new file mode 100644
index 0000000000000..7598ef8e7ea4c
--- /dev/null
+++ b/tests/ui/typeck/gather-locals-twice.stderr
@@ -0,0 +1,20 @@
+error[E0368]: binary assignment operation `+=` cannot be applied to type `()`
+ --> $DIR/gather-locals-twice.rs:4:5
+ |
+LL | () += { let x; };
+ | --^^^^^^^^^^^^^^
+ | |
+ | cannot use `+=` on type `()`
+
+error[E0067]: invalid left-hand side of assignment
+ --> $DIR/gather-locals-twice.rs:4:8
+ |
+LL | () += { let x; };
+ | -- ^^
+ | |
+ | cannot assign to this expression
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0067, E0368.
+For more information about an error, try `rustc --explain E0067`.