Fix overflow in error emitter

compiler/rustc_errors/src/emitter.rs

@@ -2303,22 +2303,25 @@ impl EmitterWriter {
 
         // Colorize addition/replacements with green.
         for &SubstitutionHighlight { start, end } in highlight_parts {
-            // Account for tabs when highlighting (#87972).
-            let tabs: usize = line_to_add
-                .chars()
-                .take(start)
-                .map(|ch| match ch {
-                    '\t' => 3,
-                    _ => 0,
-                })
-                .sum();
-            buffer.set_style_range(
-                *row_num,
-                max_line_num_len + 3 + start + tabs,
-                max_line_num_len + 3 + end + tabs,
-                Style::Addition,
-                true,
-            );
+            // This is a no-op for empty ranges
+            if start != end {
+                // Account for tabs when highlighting (#87972).
+                let tabs: usize = line_to_add
+                    .chars()
+                    .take(start)
+                    .map(|ch| match ch {
+                        '\t' => 3,
+                        _ => 0,
+                    })
+                    .sum();
+                buffer.set_style_range(
+                    *row_num,
+                    max_line_num_len + 3 + start + tabs,
+                    max_line_num_len + 3 + end + tabs,
+                    Style::Addition,
+                    true,
+                );
+            }
         }
         *row_num += 1;
     }

compiler/rustc_errors/src/lib.rs

@@ -330,12 +330,11 @@ impl CodeSuggestion {
                     });
                     buf.push_str(&part.snippet);
                     let cur_hi = sm.lookup_char_pos(part.span.hi());
-                    if cur_hi.line == cur_lo.line && !part.snippet.is_empty() {
-                        // Account for the difference between the width of the current code and the
-                        // snippet being suggested, so that the *later* suggestions are correctly
-                        // aligned on the screen.
-                        acc += len - (cur_hi.col.0 - cur_lo.col.0) as isize;
-                    }
+                    // Account for the difference between the width of the current code and the
+                    // snippet being suggested, so that the *later* suggestions are correctly
+                    // aligned on the screen. Note that cur_hi and cur_lo can be on different
+                    // lines, so cur_hi.col can be smaller than cur_lo.col
+                    acc += len - (cur_hi.col.0 as isize - cur_lo.col.0 as isize);
                     prev_hi = cur_hi;
                     prev_line = sf.get_line(prev_hi.line - 1);
                     for line in part.snippet.split('\n').skip(1) {

tests/ui/suggestions/issue-109854.rs

@@ -0,0 +1,12 @@
+fn generate_setter() {
+    String::with_capacity(
+    //~^ ERROR this function takes 1 argument but 3 arguments were supplied
+    generate_setter,
+    r#"
+pub(crate) struct Person<T: Clone> {}
+"#,
+     r#""#,
+    );
+}
+
+fn main() {}

tests/ui/suggestions/issue-109854.stderr

@@ -0,0 +1,31 @@
+error[E0061]: this function takes 1 argument but 3 arguments were supplied
+  --> $DIR/issue-109854.rs:2:5
+   |
+LL |       String::with_capacity(
+   |       ^^^^^^^^^^^^^^^^^^^^^
+...
+LL | /     r#"
+LL | | pub(crate) struct Person<T: Clone> {}
+LL | | "#,
+   | |__- unexpected argument of type `&'static str`
+LL |        r#""#,
+   |        ----- unexpected argument of type `&'static str`
+   |
+note: expected `usize`, found fn item
+  --> $DIR/issue-109854.rs:4:5
+   |
+LL |     generate_setter,
+   |     ^^^^^^^^^^^^^^^
+   = note: expected type `usize`
+           found fn item `fn() {generate_setter}`
+note: associated function defined here
+  --> $SRC_DIR/alloc/src/string.rs:LL:COL
+help: remove the extra arguments
+   |
+LL -     generate_setter,
+LL +     /* usize */,
+   |
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0061`.

tests/ui/suggestions/issue-94171.rs

@@ -0,0 +1,5 @@
+fn L(]{match
+(; {`
+//~^^ ERROR mismatched closing delimiter
+//~^^ ERROR unknown start of token
+//~ ERROR this file contains an unclosed delimiter

tests/ui/suggestions/issue-94171.stderr

@@ -0,0 +1,36 @@
+error: unknown start of token: `
+  --> $DIR/issue-94171.rs:2:5
+   |
+LL | (; {`
+   |     ^
+   |
+help: Unicode character '`' (Grave Accent) looks like ''' (Single Quote), but it is not
+   |
+LL | (; {'
+   |     ~
+
+error: mismatched closing delimiter: `]`
+  --> $DIR/issue-94171.rs:1:5
+   |
+LL | fn L(]{match
+   |     ^^ mismatched closing delimiter
+   |     |
+   |     unclosed delimiter
+
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-94171.rs:5:52
+   |
+LL | fn L(]{match
+   |      -- unclosed delimiter
+   |      |
+   |      missing open `[` for this delimiter
+LL | (; {`
+   | -  - unclosed delimiter
+   | |
+   | unclosed delimiter
+...
+LL |
+   |                                                    ^
+
+error: aborting due to 3 previous errors
+