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//! Processing errors.
use std::{error, fmt};
use crate::ReadError;
/// Location of a `Resource`: a function argument or a return type.
#[derive(Debug)]
pub enum Location {
/// Argument with the specified zero-based index.
Arg(usize),
/// Return type with the specified zero-based index.
ReturnType(usize),
}
impl fmt::Display for Location {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Arg(idx) => write!(formatter, "arg #{idx}"),
Self::ReturnType(idx) => write!(formatter, "return type #{idx}"),
}
}
}
/// Errors that can occur when [processing] a WASM module.
///
/// [processing]: super::Processor::process()
#[derive(Debug)]
#[non_exhaustive]
pub enum Error {
/// Error reading the custom section with function declarations from the module.
Read(ReadError),
/// Error parsing the WASM module.
Wasm(anyhow::Error),
/// Unexpected type of an import (expected a function).
UnexpectedImportType {
/// Name of the module.
module: String,
/// Name of the function.
name: String,
},
/// Missing exported function with the enclosed name.
NoExport(String),
/// Unexpected type of an export (expected a function).
UnexpectedExportType(String),
/// Imported or exported function has unexpected arity.
UnexpectedArity {
/// Name of the module; `None` for exported functions.
module: Option<String>,
/// Name of the function.
name: String,
/// Expected arity of the function.
expected_arity: usize,
/// Actual arity of the function.
real_arity: usize,
},
/// Argument or return type of a function has unexpected type.
UnexpectedType {
/// Name of the module; `None` for exported functions.
module: Option<String>,
/// Name of the function.
name: String,
/// Location of an argument / return type in the function.
location: Location,
/// Actual type of the function (the expected type is always `i32`).
real_type: walrus::ValType,
},
/// Incorrectly placed `externref` guard. This is caused by processing the WASM module
/// with external tools (e.g., `wasm-opt`) before using this processor.
IncorrectGuard {
/// Name of the function with an incorrectly placed guard.
function_name: Option<String>,
/// WASM bytecode offset of the offending guard.
code_offset: Option<u32>,
},
/// Unexpected call to a function returning `externref`. Such calls should be confined
/// in order for the processor to work properly. Like with [`Self::IncorrectGuard`],
/// such errors should only be caused by external tools (e.g., `wasm-opt`).
UnexpectedCall {
/// Name of the function containing an unexpected call.
function_name: Option<String>,
/// WASM bytecode offset of the offending call.
code_offset: Option<u32>,
},
}
impl fmt::Display for Error {
fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
const EXTERNAL_TOOL_TIP: &str = "This can be caused by an external WASM manipulation tool \
such as `wasm-opt`. Please run such tools *after* the externref processor.";
match self {
Self::Read(err) => write!(formatter, "failed reading WASM custom section: {err}"),
Self::Wasm(err) => write!(formatter, "failed reading WASM module: {err}"),
Self::UnexpectedImportType { module, name } => {
write!(
formatter,
"unexpected type of import `{module}::{name}`; expected a function"
)
}
Self::NoExport(name) => {
write!(formatter, "missing exported function `{name}`")
}
Self::UnexpectedExportType(name) => {
write!(
formatter,
"unexpected type of export `{name}`; expected a function"
)
}
Self::UnexpectedArity {
module,
name,
expected_arity,
real_arity,
} => {
let module_descr = module
.as_ref()
.map_or_else(String::new, |module| format!(" imported from `{module}`"));
write!(
formatter,
"unexpected arity for function `{name}`{module_descr}: \
expected {expected_arity}, got {real_arity}"
)
}
Self::UnexpectedType {
module,
name,
location,
real_type,
} => {
let module_descr = module
.as_ref()
.map_or_else(String::new, |module| format!(" imported from `{module}`"));
write!(
formatter,
"{location} of function `{name}`{module_descr} has unexpected type; \
expected `i32`, got {real_type}"
)
}
Self::IncorrectGuard {
function_name,
code_offset,
} => {
let function_name = function_name
.as_ref()
.map_or("(unnamed function)", String::as_str);
let code_offset = code_offset
.as_ref()
.map_or_else(String::new, |offset| format!(" at {offset}"));
write!(
formatter,
"incorrectly placed externref guard in {function_name}{code_offset}. \
{EXTERNAL_TOOL_TIP}"
)
}
Self::UnexpectedCall {
function_name,
code_offset,
} => {
let function_name = function_name
.as_ref()
.map_or("(unnamed function)", String::as_str);
let code_offset = code_offset
.as_ref()
.map_or_else(String::new, |offset| format!(" at {offset}"));
write!(
formatter,
"unexpected call to an `externref`-returning function \
in {function_name}{code_offset}. {EXTERNAL_TOOL_TIP}"
)
}
}
}
}
impl From<ReadError> for Error {
fn from(err: ReadError) -> Self {
Self::Read(err)
}
}
impl error::Error for Error {
fn source(&self) -> Option<&(dyn error::Error + 'static)> {
match self {
Self::Read(err) => Some(err),
Self::Wasm(err) => Some(err.as_ref()),
_ => None,
}
}
}