compiletest: Add LineNumber newtype to avoid +1 magic here and there

Start small. If it works well we can increase usage bit by bit as time
passes.

Note that we keep using "0" to represent "no specific line" because
changing to `Option<LineNumber>` everywhere is much bigger and noisier
change. That can be done later if wanted.

Author: Enselic

src/tools/compiletest/src/directives.rs

@@ -29,6 +29,8 @@ mod directive_names;
 mod file;
 mod handlers;
 mod line;
+mod line_number;
+pub(crate) use line_number::LineNumber;
 mod needs;
 #[cfg(test)]
 mod tests;
@@ -591,7 +593,7 @@ fn iter_directives(
         ];
         // Process the extra implied directives, with a dummy line number of 0.
         for directive_str in extra_directives {
-            let directive_line = line_directive(testfile, 0, directive_str)
+            let directive_line = line_directive(testfile, LineNumber::none(), directive_str)
                 .unwrap_or_else(|| panic!("bad extra-directive line: {directive_str:?}"));
             it(&directive_line);
         }

src/tools/compiletest/src/directives/file.rs

@@ -1,5 +1,6 @@
 use camino::Utf8Path;
 
+use crate::directives::LineNumber;
 use crate::directives::line::{DirectiveLine, line_directive};
 
 pub(crate) struct FileDirectives<'a> {
@@ -12,6 +13,8 @@ impl<'a> FileDirectives<'a> {
         let mut lines = vec![];
 
         for (line_number, ln) in (1..).zip(file_contents.lines()) {
+            let line_number = LineNumber::from_one_based(line_number);
+
             let ln = ln.trim();
 
             if let Some(directive_line) = line_directive(path, line_number, ln) {

src/tools/compiletest/src/directives/line.rs

@@ -2,13 +2,15 @@ use std::fmt;
 
 use camino::Utf8Path;
 
+use crate::directives::LineNumber;
+
 const COMPILETEST_DIRECTIVE_PREFIX: &str = "//@";
 
 /// If the given line begins with the appropriate comment prefix for a directive,
 /// returns a struct containing various parts of the directive.
 pub(crate) fn line_directive<'a>(
     file_path: &'a Utf8Path,
-    line_number: usize,
+    line_number: LineNumber,
     original_line: &'a str,
 ) -> Option<DirectiveLine<'a>> {
     // Ignore lines that don't start with the comment prefix.
@@ -60,7 +62,7 @@ pub(crate) struct DirectiveLine<'a> {
     /// Mostly used for diagnostics, but some directives (e.g. `//@ pp-exact`)
     /// also use it to compute a value based on the filename.
     pub(crate) file_path: &'a Utf8Path,
-    pub(crate) line_number: usize,
+    pub(crate) line_number: LineNumber,
 
     /// Some test directives start with a revision name in square brackets
     /// (e.g. `[foo]`), and only apply to that revision of the test.

src/tools/compiletest/src/directives/line_number.rs

@@ -0,0 +1,30 @@
+/// A line number in a file. Internally the first line has index 1.
+/// If it is 0 it means "no specific line" (used e.g. for implied directives).
+/// When displayed, the first line is 1.
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct LineNumber(usize);
+
+impl LineNumber {
+    /// Create a LineNumber from a zero-based line index. I.e. if `zero_based`
+    /// is `0` it means "the first line".
+    pub(crate) fn from_zero_based(zero_based: usize) -> Self {
+        // Ensure to panic on overflow.
+        LineNumber(zero_based.strict_add(1))
+    }
+
+    pub(crate) fn from_one_based(one_based: usize) -> LineNumber {
+        // You can't pass zero here. Use .none() for "no specific line".
+        assert!(one_based > 0);
+        LineNumber(one_based)
+    }
+
+    pub(crate) fn none() -> LineNumber {
+        LineNumber(0)
+    }
+}
+
+impl std::fmt::Display for LineNumber {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}

src/tools/compiletest/src/directives/tests.rs

@@ -6,8 +6,8 @@ use semver::Version;
 use crate::common::{Config, Debugger, TestMode};
 use crate::directives::{
     self, AuxProps, DIRECTIVE_HANDLERS_MAP, DirectivesCache, EarlyProps, Edition, EditionRange,
-    FileDirectives, KNOWN_DIRECTIVE_NAMES_SET, extract_llvm_version, extract_version_range,
-    line_directive, parse_edition, parse_normalize_rule,
+    FileDirectives, KNOWN_DIRECTIVE_NAMES_SET, LineNumber, extract_llvm_version,
+    extract_version_range, line_directive, parse_edition, parse_normalize_rule,
 };
 use crate::executor::{CollectedTestDesc, ShouldFail};
 
@@ -1000,7 +1000,8 @@ fn parse_edition_range(line: &str) -> Option<EditionRange> {
     let config = cfg().build();
 
     let line_with_comment = format!("//@ {line}");
-    let line = line_directive(Utf8Path::new("tmp.rs"), 0, &line_with_comment).unwrap();
+    let line =
+        line_directive(Utf8Path::new("tmp.rs"), LineNumber::none(), &line_with_comment).unwrap();
 
     super::parse_edition_range(&config, &line)
 }

src/tools/compiletest/src/runtest/debugger.rs

@@ -4,16 +4,17 @@ use std::io::{BufRead, BufReader};
 
 use camino::{Utf8Path, Utf8PathBuf};
 
+use crate::directives::LineNumber;
 use crate::runtest::ProcRes;
 
 /// Representation of information to invoke a debugger and check its output
 pub(super) struct DebuggerCommands {
     /// Commands for the debuuger
     pub commands: Vec<String>,
     /// Lines to insert breakpoints at
-    pub breakpoint_lines: Vec<usize>,
+    pub breakpoint_lines: Vec<LineNumber>,
     /// Contains the source line number to check and the line itself
-    check_lines: Vec<(usize, String)>,
+    check_lines: Vec<(LineNumber, String)>,
     /// Source file name
     file: Utf8PathBuf,
 }
@@ -26,15 +27,14 @@ impl DebuggerCommands {
         let mut breakpoint_lines = vec![];
         let mut commands = vec![];
         let mut check_lines = vec![];
-        let mut counter = 0;
         let reader = BufReader::new(File::open(file.as_std_path()).unwrap());
         for (line_no, line) in reader.lines().enumerate() {
-            counter += 1;
             let line = line.map_err(|e| format!("Error while parsing debugger commands: {}", e))?;
+            let line_number = LineNumber::from_zero_based(line_no);
 
             // Breakpoints appear on lines with actual code, typically at the end of the line.
             if line.contains("#break") {
-                breakpoint_lines.push(counter);
+                breakpoint_lines.push(line_number);
                 continue;
             }
 
@@ -46,7 +46,7 @@ impl DebuggerCommands {
                 commands.push(command);
             }
             if let Some(pattern) = parse_name_value(&line, &check_directive) {
-                check_lines.push((line_no, pattern));
+                check_lines.push((line_number, pattern));
             }
         }
 
@@ -88,15 +88,14 @@ impl DebuggerCommands {
             );
 
             for (src_lineno, err_line) in missing {
-                write!(msg, "\n    ({fname}:{num}) `{err_line}`", num = src_lineno + 1).unwrap();
+                write!(msg, "\n    ({fname}:{src_lineno}) `{err_line}`").unwrap();
             }
 
             if !found.is_empty() {
                 let init = "\nthe following subset of check directive(s) was found successfully:";
                 msg.push_str(init);
                 for (src_lineno, found_line) in found {
-                    write!(msg, "\n    ({fname}:{num}) `{found_line}`", num = src_lineno + 1)
-                        .unwrap();
+                    write!(msg, "\n    ({fname}:{src_lineno}) `{found_line}`").unwrap();
                 }
             }