use super::Parser;
use crate::ast::{Ident, Literal, PathStart, Pattern};
use crate::error::{V0001, V0002};
use crate::span::Span;
use crate::token::TokenKind;
impl<'a> Parser<'a> {
pub(super) fn parse_pattern(&mut self) -> Result<Pattern, ()> {
match self.peek() {
Some(TokenKind::Identifier(name)) if name == "_" => {
let token = self.bump().expect("peek just confirmed a token is present");
Ok(Pattern::Wildcard(token.span))
}
Some(TokenKind::CrateKw | TokenKind::SelfKw | TokenKind::SuperKw)
if self.peek_at(1) == Some(&TokenKind::ColonColon) =>
{
self.parse_path_pattern()
}
Some(TokenKind::Identifier(_)) => self.parse_path_pattern(),
Some(
TokenKind::IntegerLiteral(_)
| TokenKind::FloatLiteral(_)
| TokenKind::StringLiteral(_)
| TokenKind::BoolLiteral(_)
| TokenKind::Minus,
) => self.parse_literal_pattern(),
Some(TokenKind::DotDot) => {
let span = self.current_span();
self.bump();
self.push_error(
V0001,
span,
"rest patterns (`..`) are not supported in Varyk",
);
Err(())
}
Some(TokenKind::Mut) => {
let span = self.current_span();
self.bump();
self.push_error(
V0001,
span,
"`mut` is not supported in a pattern in Varyk; write `let mut x = x;` \
inside the arm instead",
);
Err(())
}
Some(TokenKind::ReservedKeyword(word)) if word == "ref" => {
let span = self.current_span();
self.bump();
self.push_error(
V0001,
span,
"`ref` is not supported in a pattern in Varyk; write `let mut x = x;` \
inside the arm instead",
);
Err(())
}
Some(TokenKind::Hash) => {
self.push_expected("a pattern");
Err(())
}
_ => {
let span = self.current_span();
self.bump();
self.push_error(
V0001,
span,
"only `_`, a name, a literal, a range, or a variant can be a pattern in Varyk",
);
Err(())
}
}
}
pub(super) fn reject_alternatives(&mut self) -> Result<(), ()> {
if self.peek() != Some(&TokenKind::Pipe) {
return Ok(());
}
let span = self.current_span();
self.push_error(
V0001,
span,
"alternatives (`a | b`) in a pattern are not supported in Varyk; write one arm for \
each",
);
Err(())
}
fn parse_literal_pattern(&mut self) -> Result<Pattern, ()> {
let (start, start_span) = self.parse_pattern_literal()?;
match self.peek() {
Some(TokenKind::DotDotEq) => {
self.bump();
let (end, end_span) = self.parse_pattern_literal()?;
Ok(Pattern::Range {
start,
end,
span: self.span_from(start_span, end_span),
})
}
Some(TokenKind::DotDot) => {
let dotdot_span = self.current_span();
self.bump();
self.push_error(
V0001,
self.span_from(start_span, dotdot_span),
"a range pattern includes both ends in Varyk; write it with `..=`, as in \
`0..=9`",
);
Err(())
}
_ => Ok(Pattern::Literal(start, start_span)),
}
}
pub(super) fn parse_pattern_literal(&mut self) -> Result<(Literal, Span), ()> {
let start = self.current_span();
let negative = self.bump_if(&TokenKind::Minus);
let literal = match self.peek() {
Some(TokenKind::IntegerLiteral(text)) => Some(Literal::Int {
text: text.clone(),
negative,
}),
Some(TokenKind::FloatLiteral(text)) => Some(Literal::Float {
text: text.clone(),
negative,
}),
Some(TokenKind::StringLiteral(text)) if !negative => Some(Literal::Str(text.clone())),
Some(TokenKind::BoolLiteral(value)) if !negative => Some(Literal::Bool(*value)),
_ => None,
};
let span = self.current_span();
let Some(literal) = literal else {
let what = if negative {
"a number after `-`"
} else {
"a literal"
};
self.push_error(V0002, span, format!("expected {what}"));
return Err(());
};
self.bump();
Ok((literal, self.span_from(start, span)))
}
fn parse_path_pattern(&mut self) -> Result<Pattern, ()> {
let dotted = self.parse_dotted_path("a pattern")?;
let path_span = dotted.span;
match self.peek() {
Some(TokenKind::LBrace) => {
let (fields, group_span) = self.parse_field_patterns()?;
let (path, name) = self.path_and_name(dotted);
Ok(Pattern::Struct {
path,
name,
fields,
span: self.span_from(path_span, group_span),
})
}
Some(TokenKind::LParen) => {
let (fields, group_span) = self.parse_positional_patterns()?;
let (path, name) = self.path_and_name(dotted);
Ok(Pattern::Variant {
path,
name,
fields,
span: self.span_from(path_span, group_span),
})
}
_ if dotted.leading == PathStart::None && dotted.segments.len() == 1 => {
let mut segments = dotted.segments;
Ok(Pattern::Name(segments.pop().expect("one segment")))
}
_ => {
let (path, name) = self.path_and_name(dotted);
Ok(Pattern::Variant {
path,
name,
fields: Vec::new(),
span: path_span,
})
}
}
}
fn parse_positional_patterns(&mut self) -> Result<(Vec<Pattern>, Span), ()> {
let lparen = self.bump().expect("caller confirmed `(`");
let mut fields = Vec::new();
if self.peek() != Some(&TokenKind::RParen) {
loop {
fields.push(self.parse_pattern()?);
self.reject_alternatives()?;
if self.bump_if(&TokenKind::Comma) {
if self.peek() == Some(&TokenKind::RParen) {
break;
}
continue;
}
break;
}
}
let rparen = self.expect(TokenKind::RParen, "`)`")?;
Ok((fields, self.span_from(lparen.span, rparen.span)))
}
fn parse_field_patterns(&mut self) -> Result<(Vec<(Ident, Pattern)>, Span), ()> {
let lbrace = self.bump().expect("caller confirmed `{`");
let mut fields = Vec::new();
if self.peek() != Some(&TokenKind::RBrace) {
loop {
if self.peek() == Some(&TokenKind::DotDot) {
let span = self.current_span();
self.push_error(
V0001,
span,
"`..` is not supported in a pattern with named fields; name every \
field, and write `name: _` for one you do not need",
);
return Err(());
}
let name = self.expect_identifier("a field name")?;
let pattern = if self.bump_if(&TokenKind::Colon) {
self.parse_pattern()?
} else {
Pattern::Name(name.clone())
};
self.reject_alternatives()?;
fields.push((name, pattern));
if self.bump_if(&TokenKind::Comma) {
if self.peek() == Some(&TokenKind::RBrace) {
break;
}
continue;
}
break;
}
}
let rbrace = self.expect(TokenKind::RBrace, "`}`")?;
Ok((fields, self.span_from(lbrace.span, rbrace.span)))
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::ast::{Expr, ExprKind, Literal, Path};
use crate::error::SyntaxError;
use crate::lex;
use crate::source::SourceFile;
use crate::span::FileId;
fn parse(src: &str) -> (Result<Expr, ()>, Vec<SyntaxError>) {
let file = SourceFile::new(FileId(0), "test.vr", src);
let (tokens, lex_errors) = lex(&file);
assert!(
lex_errors.is_empty(),
"unexpected lex errors: {lex_errors:?}"
);
let mut parser = Parser::new(&tokens, FileId(0));
let expr = parser.parse_expr();
(expr, parser.errors().to_vec())
}
fn parse_ok(src: &str) -> Expr {
let (expr, errors) = parse(src);
assert!(
errors.is_empty(),
"unexpected errors parsing {src:?}: {errors:?}"
);
expr.unwrap_or_else(|()| panic!("expected {src:?} to parse"))
}
fn first_pattern(pattern: &str) -> Pattern {
let expr = parse_ok(&format!("match x {{ {pattern} => 0, _ => 1 }}"));
match expr.kind {
ExprKind::Match { mut arms, .. } => arms.remove(0).pattern,
other => panic!("expected a match, got {other:?}"),
}
}
fn pattern_error(pattern: &str) -> SyntaxError {
let (expr, errors) = parse(&format!("match x {{ {pattern} => 0, _ => 1 }}"));
assert!(expr.is_err(), "{pattern} must not parse");
assert_eq!(errors.len(), 1, "{pattern}: {errors:?}");
errors[0].clone()
}
fn path_name(expr: &Expr) -> &str {
match &expr.kind {
ExprKind::Path { name, .. } => &name.name,
other => panic!("expected a Path, got {other:?}"),
}
}
fn prefix_and_segments(path: &Path) -> (&'static str, Vec<&str>) {
let leading = match path.leading {
PathStart::Crate => "crate",
PathStart::SelfMod => "self",
PathStart::Super => "super",
PathStart::None => "",
};
(
leading,
path.segments.iter().map(|s| s.name.as_str()).collect(),
)
}
fn int(text: &str, negative: bool) -> Literal {
Literal::Int {
text: text.to_string(),
negative,
}
}
#[test]
fn match_with_wildcard_and_name_pattern() {
let src = "match x { _ => 1, n => n, }";
let expr = parse_ok(src);
assert_eq!(expr.span.start, 0);
assert_eq!(expr.span.end, src.len() as u32);
match &expr.kind {
ExprKind::Match { scrutinee, arms } => {
assert_eq!(path_name(scrutinee), "x");
assert_eq!(arms.len(), 2);
assert!(matches!(arms[0].pattern, Pattern::Wildcard(_)));
match &arms[1].pattern {
Pattern::Name(name) => assert_eq!(name.name, "n"),
other => panic!("expected a name pattern, got {other:?}"),
}
}
other => panic!("expected a match, got {other:?}"),
}
}
#[test]
fn match_variant_pattern_with_fields() {
let expr = parse_ok("match shape { Shape::Circle(r) => 1, Shape::Point => 0 }");
match &expr.kind {
ExprKind::Match { arms, .. } => {
assert_eq!(arms.len(), 2);
match &arms[0].pattern {
Pattern::Variant {
path, name, fields, ..
} => {
let path = path.as_ref().expect("one segment: the type");
assert_eq!(path.segments.len(), 1);
assert_eq!(path.segments[0].name, "Shape");
assert_eq!(name.name, "Circle");
assert_eq!(fields.len(), 1);
match &fields[0] {
Pattern::Name(name) => assert_eq!(name.name, "r"),
other => panic!("expected a name pattern, got {other:?}"),
}
}
other => panic!("expected a variant pattern, got {other:?}"),
}
match &arms[1].pattern {
Pattern::Variant {
name, fields, span, ..
} => {
assert_eq!(name.name, "Point");
assert!(fields.is_empty());
assert_eq!(span.end, name.span.end, "no parentheses");
}
other => panic!("expected a variant pattern, got {other:?}"),
}
}
other => panic!("expected a match, got {other:?}"),
}
}
#[test]
fn match_unqualified_variant_pattern_with_wildcard_field() {
match first_pattern("Some(_)") {
Pattern::Variant {
path, name, fields, ..
} => {
assert!(path.is_none());
assert_eq!(name.name, "Some");
assert!(matches!(fields[0], Pattern::Wildcard(_)));
}
other => panic!("expected a variant pattern, got {other:?}"),
}
}
#[test]
fn match_module_qualified_variant_pattern() {
match first_pattern("geo::Shape::Point") {
Pattern::Variant { path, name, .. } => {
let path = path.expect("two segments");
let names: Vec<&str> = path.segments.iter().map(|s| s.name.as_str()).collect();
assert_eq!(names, vec!["geo", "Shape"]);
assert_eq!(name.name, "Point");
}
other => panic!("expected a variant pattern, got {other:?}"),
}
}
#[test]
fn keyword_prefixed_variant_pattern_parses() {
let expr = parse_ok("match k { crate::shop::Kind::Word => 0, super::Kind::Other(n) => n }");
let ExprKind::Match { arms, .. } = &expr.kind else {
panic!("expected a match, got {expr:?}");
};
let expected = [
("crate", vec!["shop", "Kind"], "Word", 0),
("super", vec!["Kind"], "Other", 1),
];
for (arm, (leading, segments, variant, count)) in arms.iter().zip(expected) {
let Pattern::Variant {
path, name, fields, ..
} = &arm.pattern
else {
panic!("expected a variant pattern, got {:?}", arm.pattern);
};
let path = path.as_ref().expect("a module path");
assert_eq!(prefix_and_segments(path), (leading, segments));
assert_eq!(name.name, variant);
assert_eq!(fields.len(), count);
}
}
#[test]
fn nested_variant_pattern() {
let Pattern::Variant { name, fields, .. } = first_pattern("Some(Shape::Circle(r))") else {
panic!("expected a variant pattern");
};
assert_eq!(name.name, "Some");
let Pattern::Variant {
path, name, fields, ..
} = &fields[0]
else {
panic!("expected a nested variant pattern, got {fields:?}");
};
assert_eq!(path.as_ref().map(|p| p.segments.len()), Some(1));
assert_eq!(name.name, "Circle");
assert!(matches!(&fields[0], Pattern::Name(n) if n.name == "r"));
}
#[test]
fn named_field_variant_pattern_with_a_literal_and_a_shorthand() {
let src = "Event::Click { x: 0, y }";
let Pattern::Struct {
path,
name,
fields,
span,
} = first_pattern(src)
else {
panic!("expected a struct pattern");
};
assert_eq!(path.map(|p| p.segments.len()), Some(1));
assert_eq!(name.name, "Click");
assert_eq!(span.end - span.start, src.len() as u32);
assert_eq!(fields.len(), 2);
assert_eq!(fields[0].0.name, "x");
assert!(matches!(&fields[0].1, Pattern::Literal(lit, _) if *lit == int("0", false)));
assert_eq!(fields[1].0.name, "y");
assert!(matches!(&fields[1].1, Pattern::Name(n) if n.name == "y"));
}
#[test]
fn named_field_variant_pattern_with_wildcards() {
let Pattern::Struct { fields, .. } = first_pattern("Event::Click { x: _, y: _ }") else {
panic!("expected a struct pattern");
};
assert_eq!(fields.len(), 2);
assert!(
fields
.iter()
.all(|(_, p)| matches!(p, Pattern::Wildcard(_)))
);
}
#[test]
fn literal_patterns() {
let cases = [
("\"yes\"", Literal::Str("yes".to_string())),
("-1", int("1", true)),
("42", int("42", false)),
("true", Literal::Bool(true)),
("false", Literal::Bool(false)),
(
"1.5",
Literal::Float {
text: "1.5".to_string(),
negative: false,
},
),
];
for (src, expected) in cases {
match first_pattern(src) {
Pattern::Literal(literal, span) => {
assert_eq!(literal, expected, "{src}");
assert_eq!(span.end - span.start, src.len() as u32, "{src}");
}
other => panic!("{src}: expected a literal pattern, got {other:?}"),
}
}
}
#[test]
fn range_pattern() {
match first_pattern("90..=100") {
Pattern::Range { start, end, span } => {
assert_eq!(start, int("90", false));
assert_eq!(end, int("100", false));
assert_eq!(span.end - span.start, 8);
}
other => panic!("expected a range pattern, got {other:?}"),
}
match first_pattern("-5..=-1") {
Pattern::Range { start, end, .. } => {
assert_eq!(start, int("5", true));
assert_eq!(end, int("1", true));
}
other => panic!("expected a range pattern, got {other:?}"),
}
}
#[test]
fn range_pattern_inside_a_variant() {
let Pattern::Variant { fields, .. } = first_pattern("Some(0..=9)") else {
panic!("expected a variant pattern");
};
assert!(matches!(&fields[0], Pattern::Range { .. }));
}
#[test]
fn exclusive_range_pattern_is_v0001_naming_the_inclusive_one() {
let error = pattern_error("0..5");
assert_eq!(error.code, V0001);
assert_eq!(
error.message,
"a range pattern includes both ends in Varyk; write it with `..=`, as in `0..=9`"
);
}
#[test]
fn match_mut_field_is_v0001_naming_mut() {
let error = pattern_error("Some(mut x)");
assert_eq!(error.code, V0001);
assert!(
error.message.contains("mut") && error.message.contains("let mut x = x;"),
"{error:?}"
);
}
#[test]
fn match_ref_field_is_v0001_naming_ref() {
let error = pattern_error("Some(ref x)");
assert_eq!(error.code, V0001);
assert!(
error.message.contains("ref") && error.message.contains("let mut x = x;"),
"{error:?}"
);
}
#[test]
fn match_rest_pattern_is_v0001() {
for pattern in ["..", "Some(..)"] {
let error = pattern_error(pattern);
assert_eq!(error.code, V0001);
assert!(error.message.contains("rest"), "{pattern}: {error:?}");
}
}
#[test]
fn rest_in_a_named_field_pattern_is_v0001() {
let error = pattern_error("Event::Click { x, .. }");
assert_eq!(error.code, V0001);
assert_eq!(
error.message,
"`..` is not supported in a pattern with named fields; name every field, and \
write `name: _` for one you do not need"
);
}
#[test]
fn match_guard_is_v0001() {
let error = pattern_error("Some(n) if n > 0");
assert_eq!(error.code, V0001);
assert_eq!(
error.message,
"match guards (`pattern if condition`) are not supported in Varyk; write the \
condition as an `if` inside the arm"
);
}
#[test]
fn alternatives_are_v0001() {
let expected = "alternatives (`a | b`) in a pattern are not supported in Varyk; write \
one arm for each";
for pattern in ["1 | 2", "Some(1 | 2)", "Event::Click { x: 0 | 1, y }"] {
let error = pattern_error(pattern);
assert_eq!(error.code, V0001);
assert_eq!(error.message, expected, "{pattern}");
}
}
}