compiletest: Refactor and document compare_output

Author: clubby789

src/tools/compiletest/src/runtest.rs

@@ -2323,15 +2323,15 @@ impl<'test> TestCx<'test> {
                         &normalized_stdout,
                         &proc_res.stdout,
                         &expected_stdout,
-                    );
+                    ) as usize;
                 }
                 if !self.props.dont_check_compiler_stderr {
                     errors += self.compare_output(
                         stderr_kind,
                         &normalized_stderr,
                         &stderr,
                         &expected_stderr,
-                    );
+                    ) as usize;
                 }
             }
             TestOutput::Run => {
@@ -2340,9 +2340,10 @@ impl<'test> TestCx<'test> {
                     &normalized_stdout,
                     &proc_res.stdout,
                     &expected_stdout,
-                );
+                ) as usize;
                 errors +=
-                    self.compare_output(stderr_kind, &normalized_stderr, &stderr, &expected_stderr);
+                    self.compare_output(stderr_kind, &normalized_stderr, &stderr, &expected_stderr)
+                        as usize;
             }
         }
         errors
@@ -2570,21 +2571,22 @@ impl<'test> TestCx<'test> {
         }
     }
 
+    // Returns `true` if output differed and was not blessed
     fn compare_output(
         &self,
         stream: &str,
         actual: &str,
         actual_unnormalized: &str,
         expected: &str,
-    ) -> usize {
+    ) -> bool {
         let are_different = match (self.force_color_svg(), expected.find('\n'), actual.find('\n')) {
             // FIXME: We ignore the first line of SVG files
             // because the width parameter is non-deterministic.
             (true, Some(nl_e), Some(nl_a)) => expected[nl_e..] != actual[nl_a..],
             _ => expected != actual,
         };
         if !are_different {
-            return 0;
+            return false;
         }
 
         // Wrapper tools set by `runner` might provide extra output on failure,
@@ -2600,7 +2602,7 @@ impl<'test> TestCx<'test> {
             used.retain(|line| actual_lines.contains(line));
             // check if `expected` contains a subset of the lines of `actual`
             if used.len() == expected_lines.len() && (expected.is_empty() == actual.is_empty()) {
-                return 0;
+                return false;
             }
             if expected_lines.is_empty() {
                 // if we have no lines to check, force a full overwite
@@ -2659,7 +2661,7 @@ impl<'test> TestCx<'test> {
 
         println!("\nThe actual {0} differed from the expected {0}.", stream);
 
-        if self.config.bless { 0 } else { 1 }
+        if self.config.bless { false } else { true }
     }
 
     /// Returns whether to show the full stderr/stdout.

src/tools/compiletest/src/runtest/coverage.rs

@@ -46,9 +46,9 @@ impl<'test> TestCx<'test> {
             &expected_coverage_dump,
         );
 
-        if coverage_dump_errors > 0 {
+        if coverage_dump_errors {
             self.fatal_proc_rec(
-                &format!("{coverage_dump_errors} errors occurred comparing coverage output."),
+                &format!("an error occurred comparing coverage output."),
                 &proc_res,
             );
         }
@@ -146,9 +146,9 @@ impl<'test> TestCx<'test> {
             &expected_coverage,
         );
 
-        if coverage_errors > 0 {
+        if coverage_errors {
             self.fatal_proc_rec(
-                &format!("{} errors occurred comparing coverage output.", coverage_errors),
+                &format!("an error occurred comparing coverage output."),
                 &proc_res,
             );
         }

src/tools/compiletest/src/runtest/ui.rs

@@ -100,7 +100,8 @@ impl TestCx<'_> {
                 )
             });
 
-            errors += self.compare_output("fixed", &fixed_code, &fixed_code, &expected_fixed);
+            errors +=
+                self.compare_output("fixed", &fixed_code, &fixed_code, &expected_fixed) as usize;
         } else if !expected_fixed.is_empty() {
             panic!(
                 "the `//@ run-rustfix` directive wasn't found but a `*.fixed` \