From b441b801fa72dac0886b98dc68b02993dc07649e Mon Sep 17 00:00:00 2001
From: Iris Shi <0.0@owo.li>
Date: Sun, 21 Sep 2025 11:43:36 +0800
Subject: [PATCH 1/4] fix a crash in rustdoc merge finalize without input file

---
 src/librustdoc/lib.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 9871066b9eb51..904972f52d018 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -835,8 +835,10 @@ fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
         config::InputMode::NoInputMergeFinalize => {
             return wrap_return(
                 dcx,
-                run_merge_finalize(render_options)
-                    .map_err(|e| format!("could not write merged cross-crate info: {e}")),
+                rustc_span::create_session_globals_then(options.edition, &[], None, || {
+                    run_merge_finalize(render_options)
+                        .map_err(|e| format!("could not write merged cross-crate info: {e}"))
+                }),
             );
         }
     };

From e37f0fed052701f38c9b61541f565b834106ad32 Mon Sep 17 00:00:00 2001
From: Iris Shi <0.0@owo.li>
Date: Mon, 22 Sep 2025 17:32:50 +0800
Subject: [PATCH 2/4] Add regression test

---
 .../rustdoc-merge-no-input-finalize/rmake.rs  | 22 +++++++++++++++++++
 .../rustdoc-merge-no-input-finalize/sierra.rs |  1 +
 2 files changed, 23 insertions(+)
 create mode 100644 tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
 create mode 100644 tests/run-make/rustdoc-merge-no-input-finalize/sierra.rs

diff --git a/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs b/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
new file mode 100644
index 0000000000000..6df9e95829d8d
--- /dev/null
+++ b/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
@@ -0,0 +1,22 @@
+// Running --merge=finalize without an input crate root should not trigger ICE.
+// Issue: https://github.com/rust-lang/rust/issues/146646
+
+//@ needs-target-std
+
+use run_make_support::rustdoc;
+
+fn main() {
+    rustdoc()
+        .input("sierra.rs")
+        .arg("-Zunstable-options")
+        .arg("--parts-out-dir=parts")
+        .arg("--merge=none")
+        .run();
+
+    rustdoc()
+        .arg("-Zunstable-options")
+        .arg("--include-parts-dir=parts")
+        .arg("--merge=finalize")
+        .out_dir("out")
+        .run();
+}
diff --git a/tests/run-make/rustdoc-merge-no-input-finalize/sierra.rs b/tests/run-make/rustdoc-merge-no-input-finalize/sierra.rs
new file mode 100644
index 0000000000000..f8fc48341ed6b
--- /dev/null
+++ b/tests/run-make/rustdoc-merge-no-input-finalize/sierra.rs
@@ -0,0 +1 @@
+pub struct Sierra;

From ba2537b6ffdbd9979874ca029e5bd86c6b925b37 Mon Sep 17 00:00:00 2001
From: Iris Shi <0.0@owo.li>
Date: Mon, 22 Sep 2025 18:09:10 +0800
Subject: [PATCH 3/4] add exit code check

---
 .../rustdoc-merge-no-input-finalize/rmake.rs     | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs b/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
index 6df9e95829d8d..4ead8c2e56c56 100644
--- a/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
+++ b/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
@@ -3,20 +3,26 @@
 
 //@ needs-target-std
 
-use run_make_support::rustdoc;
+use run_make_support::{path, rustdoc};
 
 fn main() {
+    let out_dir = path("out");
+    let merged_dir = path("merged");
+    let parts_out_dir = path("parts");
     rustdoc()
         .input("sierra.rs")
+        .out_dir(&out_dir)
         .arg("-Zunstable-options")
-        .arg("--parts-out-dir=parts")
+        .arg(format!("--parts-out-dir={}", parts_out_dir.display()))
         .arg("--merge=none")
         .run();
 
-    rustdoc()
+    let output = rustdoc()
         .arg("-Zunstable-options")
-        .arg("--include-parts-dir=parts")
+        .out_dir(&out_dir)
+        .arg(format!("--include-parts-dir={}", parts_out_dir.display()))
         .arg("--merge=finalize")
-        .out_dir("out")
         .run();
+
+    output.assert_exit_code(0);
 }

From 42ebba214b3c570761dc99f5fc1517ad092778ac Mon Sep 17 00:00:00 2001
From: Iris Shi <0.0@owo.li>
Date: Mon, 22 Sep 2025 20:36:18 +0800
Subject: [PATCH 4/4] address review comments

---
 tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs b/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
index 4ead8c2e56c56..0b1e1948d5fcc 100644
--- a/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
+++ b/tests/run-make/rustdoc-merge-no-input-finalize/rmake.rs
@@ -16,6 +16,7 @@ fn main() {
         .arg(format!("--parts-out-dir={}", parts_out_dir.display()))
         .arg("--merge=none")
         .run();
+    assert!(parts_out_dir.join("crate-info").exists());
 
     let output = rustdoc()
         .arg("-Zunstable-options")
@@ -23,6 +24,5 @@ fn main() {
         .arg(format!("--include-parts-dir={}", parts_out_dir.display()))
         .arg("--merge=finalize")
         .run();
-
-    output.assert_exit_code(0);
+    output.assert_stderr_not_contains("error: the compiler unexpectedly panicked. this is a bug.");
 }