Fix rendering errors on very long lines (#2440)

Don't render the line, just show the filename/line number.

Closes #2439

Author: alexcrichton

crates/wit-parser/src/ast.rs

@@ -1875,17 +1875,24 @@ impl SourceMap {
         let end = end.map(|end| src.to_relative_offset(end));
         let (line, col) = src.linecol(start);
         let snippet = src.contents.lines().nth(line).unwrap_or("");
+        let line = line + 1;
+        let col = col + 1;
+
+        // If the snippet is too large then don't overload output on a terminal
+        // for example and instead just print the error. This also sidesteps
+        // Rust's restriction that `>0$` below has to be less than `u16::MAX`.
+        if snippet.len() > 500 {
+            return format!("{}:{line}:{col}: {err}", src.path);
+        }
         let mut msg = format!(
             "\
 {err}
      --> {file}:{line}:{col}
       |
  {line:4} | {snippet}
       | {marker:>0$}",
-            col + 1,
+            col,
             file = src.path,
-            line = line + 1,
-            col = col + 1,
             marker = "^",
         );
         if let Some(end) = end {

crates/wit-parser/tests/ui/parse-fail/very-large-column.wit

@@ -0,0 +1 @@
+tests/ui/parse-fail/very-large-column.wit:1:65543: expected '{', found an identifier