From 5894e7260f668548f92d8b7a25379847f88a89d4 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Sat, 24 Oct 2026 21:52:20 +0000
Subject: [PATCH] Don't re-instantiate the already-instantiated signature in
 precompute_callable_param_contracts

The signature passed in is built from the body, which generic_args has
already instantiated. Instantiating its inputs again with the same args
reinterpreted the impl's own parameters as indices into the trait
method's args, so an impl with a lifetime parameter (impl<'a> Get for
R<'a>) of a specified trait method panicked in rustc's binder.

Fixes #354

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017R2xbmrztzZ35Qy7MPCymp
---
 src/analyze/local_def.rs                   |  4 +--
 tests/ui/fail/trait_impl_lifetime_param.rs | 33 ++++++++++++++++++++++
 tests/ui/pass/trait_impl_lifetime_param.rs | 33 ++++++++++++++++++++++
 3 files changed, 67 insertions(+), 3 deletions(-)
 create mode 100644 tests/ui/fail/trait_impl_lifetime_param.rs
 create mode 100644 tests/ui/pass/trait_impl_lifetime_param.rs

diff --git a/src/analyze/local_def.rs b/src/analyze/local_def.rs
index 6a9cdf1b5..366eaf853 100644
--- a/src/analyze/local_def.rs
+++ b/src/analyze/local_def.rs
@@ -232,11 +232,9 @@ impl<'tcx, 'ctx> Analyzer<'tcx, 'ctx> {
     // `def_ty_with_args` directly.
     fn precompute_callable_param_contracts(&mut self, sig: &mir_ty::FnSig<'tcx>) {
         for input_ty in sig.inputs() {
-            let inst =
-                mir_ty::EarlyBinder::bind(*input_ty).instantiate(self.tcx, self.generic_args);
             let inst = self
                 .tcx
-                .normalize_erasing_regions(mir_ty::TypingEnv::fully_monomorphized(), inst);
+                .normalize_erasing_regions(mir_ty::TypingEnv::fully_monomorphized(), *input_ty);
             let (fn_def_id, fn_args) = match inst.kind() {
                 mir_ty::TyKind::Closure(def_id, args) => {
                     (*def_id, self.tcx.mk_args(args.as_closure().parent_args()))
diff --git a/tests/ui/fail/trait_impl_lifetime_param.rs b/tests/ui/fail/trait_impl_lifetime_param.rs
new file mode 100644
index 000000000..bafe10a89
--- /dev/null
+++ b/tests/ui/fail/trait_impl_lifetime_param.rs
@@ -0,0 +1,33 @@
+//@error-in-other-file: Unsat
+//@compile-flags: -C debug-assertions=off
+
+#[thrust_macros::context]
+trait Get {
+    #[thrust_macros::requires(true)]
+    #[thrust_macros::ensures(result >= 0)]
+    fn get(&self) -> i64;
+}
+
+struct R<'a> {
+    r: &'a i64,
+}
+
+impl<'a> thrust_models::Model for R<'a> {
+    type Ty = Self;
+}
+
+impl<'a> Get for R<'a> {
+    fn get(&self) -> i64 {
+        if *self.r >= 0 {
+            *self.r
+        } else {
+            -1
+        }
+    }
+}
+
+fn main() {
+    let x = 5;
+    let r = R { r: &x };
+    assert!(r.get() >= 0);
+}
diff --git a/tests/ui/pass/trait_impl_lifetime_param.rs b/tests/ui/pass/trait_impl_lifetime_param.rs
new file mode 100644
index 000000000..9f86f7b1f
--- /dev/null
+++ b/tests/ui/pass/trait_impl_lifetime_param.rs
@@ -0,0 +1,33 @@
+//@check-pass
+//@compile-flags: -C debug-assertions=off
+
+#[thrust_macros::context]
+trait Get {
+    #[thrust_macros::requires(true)]
+    #[thrust_macros::ensures(result >= 0)]
+    fn get(&self) -> i64;
+}
+
+struct R<'a> {
+    r: &'a i64,
+}
+
+impl<'a> thrust_models::Model for R<'a> {
+    type Ty = Self;
+}
+
+impl<'a> Get for R<'a> {
+    fn get(&self) -> i64 {
+        if *self.r >= 0 {
+            *self.r
+        } else {
+            0
+        }
+    }
+}
+
+fn main() {
+    let x = 5;
+    let r = R { r: &x };
+    assert!(r.get() >= 0);
+}