From 18c787f48f08352ad5167b99920c395e3d703f62 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 30 Mar 2025 04:21:20 +0000
Subject: [PATCH] Fix up partial res of segment in primitive resolution hack

---
 compiler/rustc_resolve/src/late.rs             |  5 +++++
 tests/ui/resolve/auxiliary/empty.rs            |  1 +
 tests/ui/resolve/prim-crate-partial-res.rs     |  8 ++++++++
 tests/ui/resolve/prim-crate-partial-res.stderr | 17 +++++++++++++++++
 4 files changed, 31 insertions(+)
 create mode 100644 tests/ui/resolve/auxiliary/empty.rs
 create mode 100644 tests/ui/resolve/prim-crate-partial-res.rs
 create mode 100644 tests/ui/resolve/prim-crate-partial-res.stderr

diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 0d23ae501f0..606d25c558a 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -4598,6 +4598,11 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                     }
                 };
 
+                // Fix up partial res of segment from `resolve_path` call.
+                if let Some(id) = path[0].id {
+                    self.r.partial_res_map.insert(id, PartialRes::new(Res::PrimTy(prim)));
+                }
+
                 PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
             }
             PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
diff --git a/tests/ui/resolve/auxiliary/empty.rs b/tests/ui/resolve/auxiliary/empty.rs
new file mode 100644
index 00000000000..bd9ec079d80
--- /dev/null
+++ b/tests/ui/resolve/auxiliary/empty.rs
@@ -0,0 +1 @@
+// Intentionally empty.
diff --git a/tests/ui/resolve/prim-crate-partial-res.rs b/tests/ui/resolve/prim-crate-partial-res.rs
new file mode 100644
index 00000000000..955f4fa2aee
--- /dev/null
+++ b/tests/ui/resolve/prim-crate-partial-res.rs
@@ -0,0 +1,8 @@
+//@ aux-build: empty.rs
+
+extern crate empty as usize;
+
+fn foo() -> usize<()> { 0 }
+//~^ ERROR type arguments are not allowed on builtin type `usize`
+
+fn main() {}
diff --git a/tests/ui/resolve/prim-crate-partial-res.stderr b/tests/ui/resolve/prim-crate-partial-res.stderr
new file mode 100644
index 00000000000..d10d37c9f1b
--- /dev/null
+++ b/tests/ui/resolve/prim-crate-partial-res.stderr
@@ -0,0 +1,17 @@
+error[E0109]: type arguments are not allowed on builtin type `usize`
+  --> $DIR/prim-crate-partial-res.rs:5:19
+   |
+LL | fn foo() -> usize<()> { 0 }
+   |             ----- ^^ type argument not allowed
+   |             |
+   |             not allowed on builtin type `usize`
+   |
+help: primitive type `usize` doesn't have generic parameters
+   |
+LL - fn foo() -> usize<()> { 0 }
+LL + fn foo() -> usize { 0 }
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0109`.