From 3dd583d5407c1d459c6539a4673e6d329903da66 Mon Sep 17 00:00:00 2001
From: Gurinder Singh <frederick.the.fool@gmail.com>
Date: Fri, 27 Sep 2024 09:49:15 +0530
Subject: [PATCH] Fix error span when arg to asm!() is a macro call

When the template string passed to asm!() is produced by
a macro call like concat!() we were producing wrong error
spans. Now in the case of a macro call we just use the entire
arg to asm!(), macro call and all, as the error span.
---
 compiler/rustc_builtin_macros/src/asm.rs      | 10 ++++++-
 tests/crashes/129503.rs                       |  7 -----
 .../ice-bad-err-span-in-template-129503.rs    | 26 +++++++++++++++++
 ...ice-bad-err-span-in-template-129503.stderr | 28 +++++++++++++++++++
 4 files changed, 63 insertions(+), 8 deletions(-)
 delete mode 100644 tests/crashes/129503.rs
 create mode 100644 tests/ui/asm/ice-bad-err-span-in-template-129503.rs
 create mode 100644 tests/ui/asm/ice-bad-err-span-in-template-129503.stderr

diff --git a/compiler/rustc_builtin_macros/src/asm.rs b/compiler/rustc_builtin_macros/src/asm.rs
index 0e1ec3b3cad..486d1dada84 100644
--- a/compiler/rustc_builtin_macros/src/asm.rs
+++ b/compiler/rustc_builtin_macros/src/asm.rs
@@ -507,6 +507,7 @@ fn expand_preparsed_asm(
 
         let msg = "asm template must be a string literal";
         let template_sp = template_expr.span;
+        let template_is_mac_call = matches!(template_expr.kind, ast::ExprKind::MacCall(_));
         let (template_str, template_style, template_span) = {
             let ExpandResult::Ready(mac) = expr_to_spanned_string(ecx, template_expr, msg) else {
                 return ExpandResult::Retry(());
@@ -596,7 +597,14 @@ fn expand_preparsed_asm(
 
         if !parser.errors.is_empty() {
             let err = parser.errors.remove(0);
-            let err_sp = template_span.from_inner(InnerSpan::new(err.span.start, err.span.end));
+            let err_sp = if template_is_mac_call {
+                // If the template is a macro call we can't reliably point to the error's
+                // span so just use the template's span as the error span (fixes #129503)
+                template_span
+            } else {
+                template_span.from_inner(InnerSpan::new(err.span.start, err.span.end))
+            };
+
             let msg = format!("invalid asm template string: {}", err.description);
             let mut e = ecx.dcx().struct_span_err(err_sp, msg);
             e.span_label(err_sp, err.label + " in asm template string");
diff --git a/tests/crashes/129503.rs b/tests/crashes/129503.rs
deleted file mode 100644
index c1ed46e5955..00000000000
--- a/tests/crashes/129503.rs
+++ /dev/null
@@ -1,7 +0,0 @@
-//@ known-bug: rust-lang/rust#129503
-
-use std::arch::asm;
-
-unsafe fn f6() {
-    asm!(concat!(r#"lJ𐏿Æ�.𐏿�"#, "r} {}"));
-}
diff --git a/tests/ui/asm/ice-bad-err-span-in-template-129503.rs b/tests/ui/asm/ice-bad-err-span-in-template-129503.rs
new file mode 100644
index 00000000000..3b4390f881a
--- /dev/null
+++ b/tests/ui/asm/ice-bad-err-span-in-template-129503.rs
@@ -0,0 +1,26 @@
+// Regression test for ICE #129503
+
+
+// Tests that we come up with decent error spans
+// when the template fed to `asm!()` is itself a
+// macro call like `concat!()` and should not ICE
+
+use std::arch::asm;
+
+fn main() {
+    // Should not ICE
+    asm!(concat!(r#"lJ𐏿Æ�.𐏿�"#, "r} {}"));
+    //~^ ERROR invalid asm template string: unmatched `}` found
+
+
+    // Macro call template: should point to
+    // everything within `asm!()` as error span
+    asm!(concat!("abc", "r} {}"));
+    //~^ ERROR invalid asm template string: unmatched `}` found
+
+
+    // Literal template: should point precisely to
+    // just the `}` as error span
+    asm!("abc", "r} {}");
+    //~^ ERROR invalid asm template string: unmatched `}` found
+}
diff --git a/tests/ui/asm/ice-bad-err-span-in-template-129503.stderr b/tests/ui/asm/ice-bad-err-span-in-template-129503.stderr
new file mode 100644
index 00000000000..ffa9362ed95
--- /dev/null
+++ b/tests/ui/asm/ice-bad-err-span-in-template-129503.stderr
@@ -0,0 +1,28 @@
+error: invalid asm template string: unmatched `}` found
+  --> $DIR/ice-bad-err-span-in-template-129503.rs:12:10
+   |
+LL |     asm!(concat!(r#"lJ𐏿Æ�.𐏿�"#, "r} {}"));
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unmatched `}` in asm template string
+   |
+   = note: if you intended to print `}`, you can escape it using `}}`
+   = note: this error originates in the macro `concat` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: invalid asm template string: unmatched `}` found
+  --> $DIR/ice-bad-err-span-in-template-129503.rs:18:10
+   |
+LL |     asm!(concat!("abc", "r} {}"));
+   |          ^^^^^^^^^^^^^^^^^^^^^^^ unmatched `}` in asm template string
+   |
+   = note: if you intended to print `}`, you can escape it using `}}`
+   = note: this error originates in the macro `concat` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: invalid asm template string: unmatched `}` found
+  --> $DIR/ice-bad-err-span-in-template-129503.rs:24:19
+   |
+LL |     asm!("abc", "r} {}");
+   |                   ^ unmatched `}` in asm template string
+   |
+   = note: if you intended to print `}`, you can escape it using `}}`
+
+error: aborting due to 3 previous errors
+