Brummel
e757b453a4
Introduces a new AST emitter module responsible for serializing AST nodes back into Myc source code. This emitter preserves leading comments and whitespace, enabling a round-trip guarantee for the parser and emitter. The documentation in `docs/BNF.md` has been updated to reflect the new syntax rules for comments, including single-line comments (`;`) and documentation comments (`;;`). The rules clarify that comments must be whole lines and that inline comments are disallowed. The lexer and AST node structures have been updated to accommodate `CommentLine` variants, allowing for different types of comments (regular, documentation, and blank lines) to be stored and processed. A new test suite `tests/comment_roundtrip.rs` has been added to verify the round-trip property of the parser and emitter across all example `.myc` files. This test ensures that parsing source code, emitting it, and then parsing the emitted code again results in the same output string. The `ast.rs` binary now includes a `--emit` flag that uses the new emitter to output the parsed source code, facilitating debugging and testing of the emitter itself.
64 lines
2.0 KiB
Rust
64 lines
2.0 KiB
Rust
use myc::ast::compiler::emitter;
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use myc::ast::parser::Parser;
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use std::fs;
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/// Verifies the round-trip property for all example scripts:
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///
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/// 1. Parse source → `ast1`
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/// 2. Emit `ast1` → `code1`
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/// 3. Parse `code1` → `ast2`
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/// 4. Emit `ast2` → `code2`
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/// 5. Assert `code1 == code2`
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///
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/// If the emitter is idempotent (a second pass produces the same output),
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/// the AST is structurally stable across round-trips.
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#[test]
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fn test_roundtrip_examples() {
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let entries = fs::read_dir("examples").expect("examples/ directory not found");
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let mut tested = 0;
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for entry in entries.filter_map(|e| e.ok()) {
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let path = entry.path();
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if path.extension().is_none_or(|ext| ext != "myc") {
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continue;
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}
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let name = path.file_name().unwrap().to_string_lossy().to_string();
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let source = fs::read_to_string(&path)
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.unwrap_or_else(|e| panic!("Failed to read {}: {}", name, e));
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// Pass 1: parse original source, emit to code1
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let mut parser1 = Parser::new(&source);
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let ast1 = parser1.parse_expression();
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assert!(
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!parser1.diagnostics.has_errors(),
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"{}: parse errors on original source: {:?}",
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name,
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parser1.diagnostics.items
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);
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let code1 = emitter::emit(&ast1);
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// Pass 2: parse emitted code1, emit to code2
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let mut parser2 = Parser::new(&code1);
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let ast2 = parser2.parse_expression();
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assert!(
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!parser2.diagnostics.has_errors(),
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"{}: parse errors on round-tripped code:\n---\n{}\n---\nErrors: {:?}",
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name,
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code1,
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parser2.diagnostics.items
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);
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let code2 = emitter::emit(&ast2);
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assert_eq!(
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code1, code2,
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"{}: emitter is not idempotent (AST changed after second round-trip)",
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name
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);
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tested += 1;
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}
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assert!(tested > 0, "No .myc example files found in examples/");
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}
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