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*_operand.rs: Improve clarity of expectation-failure errors

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This commit is contained in:
John 2023-08-23 00:19:17 -05:00
parent 8ea41b46f8
commit 7901c24d80
2 changed files with 20 additions and 16 deletions
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14
src/parser/instruction/encoding/primary_operand.rs
View File

@ -68,11 +68,11 @@ impl Parsable for PrimaryOperand {
fn parse<'text, T>(p: &Parser, stream: &mut T) -> Result<Self, Error>
where T: crate::TokenStream<'text> {
use PrimaryOperand::*;
// Try parsing as Register Direct
// Try parsing as Register (Direct)
if let Some(r) = Register::try_parse(p, stream)? {
return Ok(Self::Direct(r));
}
// Try parsing as Number Indexed
// Try parsing as Number (Indexed)
if let Some(idx) = Number::try_parse(p, stream)? {
stream.expect(Type::LParen)?;
let reg = Register::parse(p, stream)?;
@ -80,10 +80,14 @@ impl Parsable for PrimaryOperand {
return Ok(Self::Indexed(reg, idx));
}
// Or directly match any of the valid prefix markers
let token = stream.expect_any_of([Type::Indirect, Type::Absolute, Type::Immediate])?;
// Type::Register and Type::Number are included here to make error messages clearer.
// their inclusion will cause a negligible slowdown when the next token is not a prefix marker
// (a failure condition)
let token =
stream.expect_any_of([Type::Indirect, Type::Absolute, Type::Immediate, Type::Register, Type::Number])?;
Ok(match token.variant() {
Type::Indirect => {
let reg = stream.expect(Type::Register)?.parse()?;
let reg = Register::parse(p, stream)?;
match stream.expect(Type::Plus) {
Ok(_) => PostInc(reg),
Err(_) => Indirect(reg),
@ -93,7 +97,7 @@ impl Parsable for PrimaryOperand {
Type::Immediate => {
let number = Number::parse(p, stream)?;
match number.into() {
// There are two representations for the all-ones constant, since Number preserves absolute
// There are two representations for the all-ones constant, since Number preserves
// signedness.
-1 | 0xffff => MinusOne,
0 => Zero,

16
src/parser/instruction/encoding/secondary_operand.rs
View File

@ -55,28 +55,28 @@ impl Parsable for SecondaryOperand {
where T: crate::TokenStream<'text> {
use SecondaryOperand::*;
stream.allow(Type::Separator);
// Try parsing as Register Direct
// Try parsing as Register (Direct)
if let Some(r) = Register::try_parse(p, stream)? {
return Ok(Self::Direct(r));
}
// Try parsing as Number Indexed
// Try parsing as Number (Indexed)
if let Some(idx) = Number::try_parse(p, stream)? {
stream.expect(Type::LParen)?;
let reg = Register::parse(p, stream)?;
stream.expect(Type::RParen)?;
return Ok(Self::Indexed(reg, idx));
}
let token = stream.expect_any_of([Type::Absolute, Type::Immediate])?;
// Type::Register and Type::Number are included here to make error messages clearer.
// their inclusion will cause a negligible slowdown when the next token is not a prefix marker
// (a failure condition) but should not match a token
let token = stream.expect_any_of([Type::Absolute, Type::Immediate, Type::Register, Type::Number])?;
Ok(match token.variant() {
Type::Absolute => Absolute(Number::parse(p, stream)?),
Type::Immediate => {
let number = Number::parse(p, stream)?;
match number.into() {
Type::Immediate => match Number::parse(p, stream)?.into() {
0 => Zero,
1 => One,
n => Err(Error::FatSecondaryImmediate(n as isize).context(stream.context()))?,
}
}
},
_ => unreachable!("Token {token:?} passed expectation but failed match!"),
})
}