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libexpr: Support structured error classes

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While preparing PRs like #9753, I've had to change error messages in
dozens of code paths. It would be nice if instead of

    EvalError("expected 'boolean' but found '%1%'", showType(v))

we could write

    TypeError(v, "boolean")

or similar. Then, changing the error message could be a mechanical
refactor with the compiler pointing out places the constructor needs to
be changed, rather than the error-prone process of grepping through the
codebase. Structured errors would also help prevent the "same" error
from having multiple slightly different messages, and could be a first
step towards error codes / an error index.

This PR reworks the exception infrastructure in `libexpr` to
support exception types with different constructor signatures than
`BaseError`. Actually refactoring the exceptions to use structured data
will come in a future PR (this one is big enough already, as it has to
touch every exception in `libexpr`).

The core design is in `eval-error.hh`. Generally, errors like this:

    state.error("'%s' is not a string", getAttrPathStr())
      .debugThrow<TypeError>()

are transformed like this:

    state.error<TypeError>("'%s' is not a string", getAttrPathStr())
      .debugThrow()

The type annotation has moved from `ErrorBuilder::debugThrow` to
`EvalState::error`.
This commit is contained in:
Rebecca Turner 2024-01-22 17:08:29 -08:00
parent c62c21e29a
commit c6a89c1a16
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40 changed files with 653 additions and 545 deletions
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12
src/libexpr/lexer.l
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@ -146,9 +146,9 @@ or { return OR_KW; }
try {
yylval->n = boost::lexical_cast<int64_t>(yytext);
} catch (const boost::bad_lexical_cast &) {
throw ParseError({
throw ParseError(ErrorInfo{
.msg = hintfmt("invalid integer '%1%'", yytext),
.errPos = state->positions[CUR_POS],
.pos = state->positions[CUR_POS],
});
}
return INT_LIT;
@ -156,9 +156,9 @@ or { return OR_KW; }
{FLOAT} { errno = 0;
yylval->nf = strtod(yytext, 0);
if (errno != 0)
throw ParseError({
throw ParseError(ErrorInfo{
.msg = hintfmt("invalid float '%1%'", yytext),
.errPos = state->positions[CUR_POS],
.pos = state->positions[CUR_POS],
});
return FLOAT_LIT;
}
@ -285,9 +285,9 @@ or { return OR_KW; }
<INPATH_SLASH>{ANY} |
<INPATH_SLASH><<EOF>> {
throw ParseError({
throw ParseError(ErrorInfo{
.msg = hintfmt("path has a trailing slash"),
.errPos = state->positions[CUR_POS],
.pos = state->positions[CUR_POS],
});
}