START OF COMPILER

src/parser/v2/error.rs

@@ -0,0 +1,60 @@
+use super::{FilePos, FileRegion};
+
+#[derive(Debug)]
+pub struct ParserError {
+    pub msg: String,
+    pub regions: Vec<FileRegion>,
+}
+
+impl ParserError {
+    pub fn from_msg(msg: String) -> Self {
+        Self {
+            msg,
+            regions: Vec::new(),
+        }
+    }
+    pub fn at(pos: FilePos, msg: String) -> Self {
+        Self {
+            msg,
+            regions: vec![FileRegion {
+                start: pos,
+                end: pos,
+            }],
+        }
+    }
+    pub fn unexpected_end() -> Self {
+        Self::from_msg("Unexpected end of input".to_string())
+    }
+}
+
+const BEFORE: usize = 1;
+const AFTER: usize = 1;
+
+pub fn print_error(err: ParserError, file: &str) {
+    let after = if err.regions.is_empty() {""} else {":"};
+    println!("error: {}{}", err.msg, after);
+    for reg in err.regions {
+        print_region(file, reg);
+    }
+}
+
+pub fn print_region(file: &str, reg: FileRegion) {
+    let start = reg.start.line.saturating_sub(BEFORE);
+    let num_before = reg.start.line - start;
+    let mut lines = file.lines().skip(start);
+    let len = reg.end.col - reg.start.col + 1;
+    let width = format!("{}", reg.end.line + AFTER).len();
+    for i in 0..num_before + 1 {
+        println!("{:>width$} | {}", start + i, lines.next().unwrap());
+    }
+    println!(
+        "{} | {}",
+        " ".repeat(width),
+        " ".repeat(reg.start.col) + &"^".repeat(len)
+    );
+    for i in 0..AFTER {
+        if let Some(next) = lines.next() {
+            println!("{:>width$} | {}", reg.end.line + i + 1, next);
+        }
+    }
+}