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lazy fail on parse errors #139

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merged 1 commit into from
Sep 30, 2023
Merged

lazy fail on parse errors #139

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89 changes: 63 additions & 26 deletions src/grammar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1161,12 +1161,18 @@ impl Grammar {
Ok(())
}

fn do_shift(&self, symbol_iter: &mut dyn Iterator<Item = FormulaToken>, nset: &Nameset) {
fn do_shift(
&self,
symbol_iter: &mut dyn Iterator<Item = Result<FormulaToken, StmtParseError>>,
nset: &Nameset,
) -> Result<(), StmtParseError> {
if let Some(token) = symbol_iter.next() {
let token = token?;
if self.debug {
debug!(" SHIFT {:?}", as_str(nset.atom_name(token.symbol)));
}
}
Ok(())
}

fn do_reduce(formula_builder: &mut FormulaBuilder, reduce: Reduce, nset: &Nameset) {
Expand All @@ -1189,7 +1195,7 @@ impl Grammar {
/// Parses the given list of symbols into a formula syntax tree.
pub fn parse_formula(
&self,
symbol_iter: &mut impl Iterator<Item = FormulaToken>,
symbol_iter: &mut impl Iterator<Item = Result<FormulaToken, StmtParseError>>,
expected_typecodes: &[TypeCode],
convert_to_provable: bool,
nset: &Nameset,
Expand All @@ -1201,9 +1207,12 @@ impl Grammar {

let mut formula_builder = FormulaBuilder::default();
let mut symbol_enum = symbol_iter.peekable();
let mut last_token = *symbol_enum
let Ok(mut last_token) = symbol_enum
.peek()
.ok_or(StmtParseError::ParsedStatementNoTypeCode)?;
.ok_or(StmtParseError::ParsedStatementNoTypeCode)?
else {
return Err(symbol_enum.next().unwrap().unwrap_err());
};
let mut e = StackElement {
node_id: self.root,
expected_typecodes: expected_typecodes.to_vec().into_boxed_slice(),
Expand Down Expand Up @@ -1292,7 +1301,7 @@ impl Grammar {
}
}
GrammarNode::Branch { ref map } => {
if let Some(&token) = symbol_enum.peek() {
if let Some(&Ok(token)) = symbol_enum.peek() {
last_token = token;
debug!(" {:?}", as_str(nset.atom_name(token.symbol)));

Expand All @@ -1307,7 +1316,7 @@ impl Grammar {
}

// Found an atom matching one of our next nodes: SHIFT, to the next node
self.do_shift(&mut symbol_enum, nset);
self.do_shift(&mut symbol_enum, nset)?;
e.node_id = *next_node_id;
debug!(" Next Node: {:?}", e.node_id);
} else {
Expand All @@ -1333,6 +1342,9 @@ impl Grammar {
};
}
} else {
if let Some(token) = symbol_enum.next() {
token?;
}
return Err(Grammar::too_short(last_token, map, nset));
}
}
Expand Down Expand Up @@ -1401,6 +1413,47 @@ impl Iterator for FormulaTokenIter<'_> {
}
}

/// An iterator through the tokens of a math expression
#[derive(Debug)]
pub struct StmtTokenIter<'a, 'b> {
span: &'a [Span],
buffer: &'a [u8],
index: usize,
names: &'a mut NameReader<'b>,
}

impl StatementRef<'_> {
/// Returns a new iterator over tokens of a math expression.
/// `names` caches the result of any name lookups performed.
pub fn token_iter<'a, 'b>(&'a self, names: &'a mut NameReader<'b>) -> StmtTokenIter<'a, 'b> {
let range = self.statement.math_start..self.statement.proof_start;
StmtTokenIter {
span: &self.segment.segment.span_pool[range],
buffer: &self.segment.segment.buffer,
index: 1,
names,
}
}
}

impl Iterator for StmtTokenIter<'_, '_> {
type Item = Result<FormulaToken, StmtParseError>;
fn next(&mut self) -> Option<Self::Item> {
let span = *self.span.get(self.index)?;
self.index += 1;
Some(
if let Some(lookup) = self.names.lookup_symbol(span.as_ref(self.buffer)) {
Ok(FormulaToken {
symbol: lookup.atom,
span,
})
} else {
Err(StmtParseError::UnknownToken(span))
},
)
}
}

impl Grammar {
/// Parses a character string into a formula
/// As a first math token, the string is expected to contain the typecode for the formula.
Expand All @@ -1410,12 +1463,10 @@ impl Grammar {
formula_string: &str,
nset: &Arc<Nameset>,
) -> Result<Formula, StmtParseError> {
let mut symbols = FormulaTokenIter::from_str(formula_string, nset)
.collect::<Result<Vec<_>, _>>()?
.into_iter();
let mut symbols = FormulaTokenIter::from_str(formula_string, nset);
let typecode = symbols
.next()
.ok_or(StmtParseError::ParsedStatementNoTypeCode)?;
.ok_or(StmtParseError::ParsedStatementNoTypeCode)??;
let expected_typecode = if typecode.symbol == self.provable_type {
self.logic_type
} else {
Expand Down Expand Up @@ -1461,24 +1512,10 @@ impl Grammar {
as_str(nset.statement_name(sref))
);

let math_string: Result<Vec<_>, _> = sref
.math_iter()
.skip(1)
.map(|token| {
let span = sref.math_span(token.index());
if let Some(lookup) = names.lookup_symbol(token.slice) {
Ok(FormulaToken {
symbol: lookup.atom,
span,
})
} else {
Err(StmtParseError::UnknownToken(span))
}
})
.collect();
let mut math_string = sref.token_iter(names);
let convert_to_provable = typecode == self.provable_type;
let formula = self.parse_formula(
&mut math_string?.into_iter(),
&mut math_string,
&[expected_typecode],
convert_to_provable,
nset,
Expand Down
4 changes: 2 additions & 2 deletions src/grammar_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -113,7 +113,7 @@ fn test_parse_formula() {
let fmla_vec = vec![a, eq, open_parens, b, plus, a, close_parens];
let formula = grammar
.parse_formula(
&mut fmla_vec.clone().into_iter(),
&mut fmla_vec.iter().map(|t| Ok(*t)),
&[wff, class],
false,
&names,
Expand Down Expand Up @@ -213,7 +213,7 @@ fn test_setvar_as_class() {
{
let formula = grammar
.parse_formula(
&mut vec![x_symbol].into_iter(),
&mut std::iter::once(Ok(x_symbol)),
&[class_symbol],
false,
&names,
Expand Down
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