From f41055266537a3dfa9ea22970df73403e618e963 Mon Sep 17 00:00:00 2001
From: Scott Schafer <schaferjscott@gmail.com>
Date: Tue, 10 Jun 2025 04:00:02 -0600
Subject: [PATCH 1/2] test: Add rustc test with empty source

---
 tests/rustc_tests.rs | 114 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

diff --git a/tests/rustc_tests.rs b/tests/rustc_tests.rs
index 0a1c531..13924c8 100644
--- a/tests/rustc_tests.rs
+++ b/tests/rustc_tests.rs
@@ -2680,3 +2680,117 @@ LL | | */
     let renderer = Renderer::plain().anonymized_line_numbers(true);
     assert_data_eq!(renderer.render(input), expected);
 }
+
+#[test]
+#[should_panic(expected = "called `Option::unwrap()` on a `None` value")]
+fn mismatched_types1() {
+    // tests/ui/include-macros/mismatched-types.rs
+
+    let file_txt_source = r#""#;
+
+    let rust_source = r#"fn main() {
+    let b: &[u8] = include_str!("file.txt");    //~ ERROR mismatched types
+    let s: &str = include_bytes!("file.txt");   //~ ERROR mismatched types
+}"#;
+
+    let input = Level::ERROR.header("mismatched types").id("E0308").group(
+        Group::new()
+            .element(
+                Snippet::source(file_txt_source)
+                    .fold(true)
+                    .line_start(3)
+                    .origin("$DIR/file.txt")
+                    .annotation(
+                        AnnotationKind::Primary
+                            .span(0..0)
+                            .label("expected `&[u8]`, found `&str`"),
+                    ),
+            )
+            .element(
+                Snippet::source(rust_source)
+                    .origin("$DIR/mismatched-types.rs")
+                    .fold(true)
+                    .annotation(
+                        AnnotationKind::Context
+                            .span(23..28)
+                            .label("expected due to this"),
+                    )
+                    .annotation(
+                        AnnotationKind::Context
+                            .span(31..55)
+                            .label("in this macro invocation"),
+                    ),
+            )
+            .element(
+                Level::NOTE.title("expected reference `&[u8]`\n   found reference `&'static str`"),
+            ),
+    );
+
+    let expected = str![[r#"
+error[E0308]: mismatched types
+  --> $DIR/file.txt:3:1
+   |
+LL |
+   | ^ expected `&[u8]`, found `&str`
+   |
+  ::: $DIR/mismatched-types.rs:2:12
+   |
+LL |     let b: &[u8] = include_str!("file.txt");    //~ ERROR mismatched types
+   |            -----   ------------------------ in this macro invocation
+   |            |
+   |            expected due to this
+   |
+   = note: expected reference `&[u8]`
+              found reference `&'static str`
+"#]];
+    let renderer = Renderer::plain().anonymized_line_numbers(true);
+    assert_data_eq!(renderer.render(input), expected);
+}
+
+#[test]
+fn mismatched_types2() {
+    // tests/ui/include-macros/mismatched-types.rs
+
+    let source = r#"fn main() {
+    let b: &[u8] = include_str!("file.txt");    //~ ERROR mismatched types
+    let s: &str = include_bytes!("file.txt");   //~ ERROR mismatched types
+}"#;
+
+    let input = Level::ERROR.header("mismatched types").id("E0308").group(
+        Group::new()
+            .element(
+                Snippet::source(source)
+                    .origin("$DIR/mismatched-types.rs")
+                    .fold(true)
+                    .annotation(
+                        AnnotationKind::Primary
+                            .span(105..131)
+                            .label("expected `&str`, found `&[u8; 0]`"),
+                    )
+                    .annotation(
+                        AnnotationKind::Context
+                            .span(98..102)
+                            .label("expected due to this"),
+                    ),
+            )
+            .element(
+                Level::NOTE
+                    .title("expected reference `&str`\n   found reference `&'static [u8; 0]`"),
+            ),
+    );
+
+    let expected = str![[r#"
+error[E0308]: mismatched types
+  --> $DIR/mismatched-types.rs:3:19
+   |
+LL |     let s: &str = include_bytes!("file.txt");   //~ ERROR mismatched types
+   |            ----   ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&str`, found `&[u8; 0]`
+   |            |
+   |            expected due to this
+   |
+   = note: expected reference `&str`
+              found reference `&'static [u8; 0]`
+"#]];
+    let renderer = Renderer::plain().anonymized_line_numbers(true);
+    assert_data_eq!(renderer.render(input), expected);
+}

From 23242144f51cc7902d6bcc5d69420600f9426459 Mon Sep 17 00:00:00 2001
From: Scott Schafer <schaferjscott@gmail.com>
Date: Wed, 4 Jun 2025 15:16:07 -0600
Subject: [PATCH 2/2] fix: Ensure empty sources have one "line"

---
 src/renderer/source_map.rs | 15 +++++++++++++++
 tests/formatter.rs         |  1 +
 tests/rustc_tests.rs       |  1 -
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/renderer/source_map.rs b/src/renderer/source_map.rs
index d5f91a1..7401fb9 100644
--- a/src/renderer/source_map.rs
+++ b/src/renderer/source_map.rs
@@ -11,6 +11,21 @@ pub(crate) struct SourceMap<'a> {
 
 impl<'a> SourceMap<'a> {
     pub(crate) fn new(source: &'a str, line_start: usize) -> Self {
+        // Empty sources do have a "line", but it is empty, so we need to add
+        // a line with an empty string to the source map.
+        if source.is_empty() {
+            return Self {
+                lines: vec![LineInfo {
+                    line: "",
+                    line_index: line_start,
+                    start_byte: 0,
+                    end_byte: 0,
+                    end_line_size: 0,
+                }],
+                source,
+            };
+        }
+
         let mut current_index = 0;
 
         let mut mapping = vec![];
diff --git a/tests/formatter.rs b/tests/formatter.rs
index e5647b8..61277ec 100644
--- a/tests/formatter.rs
+++ b/tests/formatter.rs
@@ -303,6 +303,7 @@ fn test_only_source() {
 error: 
  --> file.rs
   |
+1 |
 "#]];
     let renderer = Renderer::plain();
     assert_data_eq!(renderer.render(input), expected);
diff --git a/tests/rustc_tests.rs b/tests/rustc_tests.rs
index 13924c8..b1505d7 100644
--- a/tests/rustc_tests.rs
+++ b/tests/rustc_tests.rs
@@ -2682,7 +2682,6 @@ LL | | */
 }
 
 #[test]
-#[should_panic(expected = "called `Option::unwrap()` on a `None` value")]
 fn mismatched_types1() {
     // tests/ui/include-macros/mismatched-types.rs