Fix wrong span for hightlight for duplicated diff lines

Author: chenyukang

compiler/rustc_errors/src/emitter.rs

@@ -2412,7 +2412,7 @@ impl HumanEmitter {
                             // too bad to begin with, so we side-step that issue here.
                             for (i, line) in snippet.lines().enumerate() {
                                 let line = normalize_whitespace(line);
-                                let row = row_num - 2 - (newlines - i - 1);
+                                let row = (row_num - 2 - (newlines - i - 1)).max(2);
                                 // On the first line, we highlight between the start of the part
                                 // span, and the end of that line.
                                 // On the last line, we highlight between the start of the line, and

tests/ui/argument-suggestions/wrong-highlight-span-extra-arguments-147070.rs

@@ -0,0 +1,30 @@
+//@ only-linux
+//@ compile-flags: --error-format=human --color=always
+
+// The hightlight span should be correct. See #147070
+struct Thingie;
+
+impl Thingie {
+    pub(crate) fn new(
+        _a: String,
+        _b: String,
+        _c: String,
+        _d: String,
+        _e: String,
+        _f: String,
+    ) -> Self {
+        unimplemented!()
+    }
+}
+
+fn main() {
+    let foo = Thingie::new(
+        String::from(""),
+        String::from(""),
+        String::from(""),
+        String::from(""),
+        String::from(""),
+        String::from(""),
+        String::from(""),
+    );
+}