slightly better error rendering

+ fixed grammar
+ added a space bteween `-` and operand when pretty printing unary rvalue of mir

Author: DigitalCodeCrafter

src/grammar.ebnf

@@ -19,6 +19,7 @@ nud = Number
     | Identifier
     | "true"
     | "false"
+    | "-", Expression
     | "(", Expression, ")"
     | "{", { Statement }, "}"
     ;

src/main.rs

@@ -1,16 +1,17 @@
-use ksi::{backend, common::diagnostics::sinks::Diagnostics, mir::{self, passes::{ConstPropagation, CopyPropagation, DeadLocalElim, Pass, run_passes}, pretty}, semantics, syntax};
+use ksi::{backend, common::diagnostics::{Diagnostic, Severity, sinks::Diagnostics}, mir::{self, passes::{ConstPropagation, CopyPropagation, DeadLocalElim, Pass, run_passes}, pretty}, semantics, syntax};
 
 
 fn main() -> Result<(), ()> {
     let file_path = std::env::args().nth(1).expect("Missing file path");
 
     let content = std::fs::read_to_string(file_path).unwrap();
+    let line_starts = line_indices(&content);
 
     let mut diagnostics = Diagnostics::empty();
     let parsed_ast = syntax::parse(&content, &mut diagnostics);
     let (typed_ast, symbols) = semantics::analyze(parsed_ast, &mut diagnostics);
     if diagnostics.has_error() {
-        eprintln!("{:#?}", diagnostics.diagnostics);
+        render_all(&content, &line_starts, &diagnostics.diagnostics);
         return Err(());
     }
 
@@ -26,9 +27,7 @@ fn main() -> Result<(), ()> {
 
     let out = backend::emit(&prog_ir, &mut diagnostics);
 
-    if diagnostics.has_error() {
-        eprintln!("{:#?}", diagnostics.diagnostics);
-    }
+    render_all(&content, &line_starts, &diagnostics.diagnostics);
 
     let pretty_ir = pretty::format_body(&prog_ir, "main");
     for line in pretty_ir.lines() {
@@ -39,3 +38,88 @@ fn main() -> Result<(), ()> {
     Ok(()) 
 }
 
+fn line_indices(src: &str) -> Vec<usize> {
+    let mut line_starts = vec![0];
+    for (i, b) in src.bytes().enumerate() {
+        if b == b'\n' {
+            line_starts.push(i + 1);
+        }
+    }
+    line_starts
+}
+
+fn line_col(src: &str, line_starts: &[usize], pos: usize) -> (usize, usize) {
+    let line = match line_starts.binary_search(&pos) {
+        Ok(i) => i,
+        Err(i) => i - 1,
+    };
+
+    let col = src[line_starts[line]..pos].chars().count();
+    (line + 1, col + 1)
+}
+
+fn get_line<'a>(src: &'a str, line_idx: usize, line_starts: &[usize]) -> &'a str {
+    let start = line_starts[line_idx];
+    let end = if line_idx + 1 < line_starts.len() {
+        line_starts[line_idx + 1] - 1
+    } else {
+        src.len()
+    };
+    &src[start..end]
+}
+
+fn print_marker(line: &str, col: usize, marker: char, message: Option<&str>) {
+    let mut pos = 0;
+    for c in line.chars().take(col - 1) {
+        if c == '\t' { pos += 4 }
+        else { pos += 1 }
+    }
+    let padding = " ".repeat(pos);
+    if let Some(msg) = message {
+        print!("{padding}{} {}\n", marker, msg);
+    } else {
+        print!("{padding}{}\n", marker)
+    }
+}
+
+fn render_diagnostic(diag: &Diagnostic, line_starts: &[usize], src: &str) {
+    let severity = match diag.severity {
+        Severity::Note => "note",
+        Severity::Warning => "warning",
+        Severity::Error => "error"
+    };
+    print!("{}: {}\n", severity, diag.message);
+
+    if let Some(span) = diag.span {
+        let loc = line_col(src, line_starts, span.start);
+        print!("  --> input:{}:{}\n", loc.0, loc.1);
+
+        let source_line = get_line(src, loc.0 - 1, line_starts);
+        print!("   |\n{:>2} | {}\n", loc.0, source_line);
+    }
+
+    for label in &diag.labels {
+        let loc = line_col(src, line_starts, label.span.start);
+        let source_line = get_line(src, loc.0 - 1, line_starts);
+        let marker = if label.is_primary { '^' } else { '-' };
+        print!("     ");
+        print_marker(source_line, loc.1, marker, label.message.as_deref());
+    }
+
+    for note in &diag.notes {
+        print!("   = {}\n", note);
+    }
+
+    println!();
+}
+
+fn render_all(src: &str, line_starts: &[usize], diags: &[Diagnostic]) {
+    let mut error_count = 0;
+    for diag in diags {
+        if diag.severity == Severity::Error { error_count += 1 }
+        render_diagnostic(diag, line_starts, src);
+    }
+    if error_count > 0 {
+        println!("error: compilation failed due to {} previous errors", error_count)
+    }
+}

src/mir/pretty.rs

@@ -46,7 +46,7 @@ pub fn format_rval(rv: &RValue) -> String {
         }
         RValue::Unary(op, val) => {
             let op_str = match op {
-                UnaryOp::Neg    => "-"
+                UnaryOp::Neg    => "- "
             };
             format!("{}{}",
                 op_str,