use crate::diagnostic_filter::ConflictingDiagnosticRuleError;
use crate::front::wgsl::parse::directive::enable_extension::{
    EnableExtension, UnimplementedEnableExtension,
};
use crate::front::wgsl::parse::directive::language_extension::{
    LanguageExtension, UnimplementedLanguageExtension,
};
use crate::front::wgsl::parse::lexer::Token;
use crate::front::wgsl::Scalar;
use crate::proc::{Alignment, ConstantEvaluatorError, ResolveError};
use crate::{SourceLocation, Span};
use codespan_reporting::diagnostic::{Diagnostic, Label};
use codespan_reporting::files::SimpleFile;
use codespan_reporting::term;
use std::borrow::Cow;
use std::ops::Range;
use termcolor::{ColorChoice, NoColor, StandardStream};
use thiserror::Error;

#[cfg(test)]
use std::mem::size_of;

#[derive(Clone, Debug)]
pub struct ParseError {
    message: String,
    // The first span should be the primary span, and the other ones should be complementary.
    labels: Vec<(Span, Cow<'static, str>)>,
    notes: Vec<String>,
}

impl ParseError {
    pub fn labels(&self) -> impl ExactSizeIterator<Item = (Span, &str)> + '_ {
        self.labels
            .iter()
            .map(|&(span, ref msg)| (span, msg.as_ref()))
    }

    pub fn message(&self) -> &str {
        &self.message
    }

    fn diagnostic(&self) -> Diagnostic<()> {
        let diagnostic = Diagnostic::error()
            .with_message(self.message.to_string())
            .with_labels(
                self.labels
                    .iter()
                    .filter_map(|label| label.0.to_range().map(|range| (label, range)))
                    .map(|(label, range)| {
                        Label::primary((), range).with_message(label.1.to_string())
                    })
                    .collect(),
            )
            .with_notes(
                self.notes
                    .iter()
                    .map(|note| format!("note: {note}"))
                    .collect(),
            );
        diagnostic
    }

    /// Emits a summary of the error to standard error stream.
    pub fn emit_to_stderr(&self, source: &str) {
        self.emit_to_stderr_with_path(source, "wgsl")
    }

    /// Emits a summary of the error to standard error stream.
    pub fn emit_to_stderr_with_path<P>(&self, source: &str, path: P)
    where
        P: AsRef<std::path::Path>,
    {
        let path = path.as_ref().display().to_string();
        let files = SimpleFile::new(path, source);
        let config = term::Config::default();
        let writer = StandardStream::stderr(ColorChoice::Auto);
        term::emit(&mut writer.lock(), &config, &files, &self.diagnostic())
            .expect("cannot write error");
    }

    /// Emits a summary of the error to a string.
    pub fn emit_to_string(&self, source: &str) -> String {
        self.emit_to_string_with_path(source, "wgsl")
    }

    /// Emits a summary of the error to a string.
    pub fn emit_to_string_with_path<P>(&self, source: &str, path: P) -> String
    where
        P: AsRef<std::path::Path>,
    {
        let path = path.as_ref().display().to_string();
        let files = SimpleFile::new(path, source);
        let config = term::Config::default();
        let mut writer = NoColor::new(Vec::new());
        term::emit(&mut writer, &config, &files, &self.diagnostic()).expect("cannot write error");
        String::from_utf8(writer.into_inner()).unwrap()
    }

    /// Returns a [`SourceLocation`] for the first label in the error message.
    pub fn location(&self, source: &str) -> Option<SourceLocation> {
        self.labels.first().map(|label| label.0.location(source))
    }
}

impl std::fmt::Display for ParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.message)
    }
}

impl std::error::Error for ParseError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        None
    }
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub enum ExpectedToken<'a> {
    Token(Token<'a>),
    Identifier,
    AfterIdentListComma,
    AfterIdentListArg,
    /// Expected: constant, parenthesized expression, identifier
    PrimaryExpression,
    /// Expected: assignment, increment/decrement expression
    Assignment,
    /// Expected: 'case', 'default', '}'
    SwitchItem,
    /// Expected: ',', ')'
    WorkgroupSizeSeparator,
    /// Expected: 'struct', 'let', 'var', 'type', ';', 'fn', eof
    GlobalItem,
    /// Expected a type.
    Type,
    /// Access of `var`, `let`, `const`.
    Variable,
    /// Access of a function
    Function,
    /// The `diagnostic` identifier of the `@diagnostic(…)` attribute.
    DiagnosticAttribute,
}

#[derive(Clone, Copy, Debug, Error, PartialEq)]
pub enum NumberError {
    #[error("invalid numeric literal format")]
    Invalid,
    #[error("numeric literal not representable by target type")]
    NotRepresentable,
    #[error("unimplemented f16 type")]
    UnimplementedF16,
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub enum InvalidAssignmentType {
    Other,
    Swizzle,
    ImmutableBinding(Span),
}

#[derive(Clone, Debug)]
pub(crate) enum Error<'a> {
    Unexpected(Span, ExpectedToken<'a>),
    UnexpectedComponents(Span),
    UnexpectedOperationInConstContext(Span),
    BadNumber(Span, NumberError),
    BadMatrixScalarKind(Span, Scalar),
    BadAccessor(Span),
    BadTexture(Span),
    BadTypeCast {
        span: Span,
        from_type: Box<str>,
        to_type: Box<str>,
    },
    BadTextureSampleType {
        span: Span,
        scalar: Scalar,
    },
    BadIncrDecrReferenceType(Span),
    InvalidResolve(ResolveError),
    InvalidForInitializer(Span),
    /// A break if appeared outside of a continuing block
    InvalidBreakIf(Span),
    InvalidGatherComponent(Span),
    InvalidConstructorComponentType(Span, i32),
    InvalidIdentifierUnderscore(Span),
    ReservedIdentifierPrefix(Span),
    UnknownAddressSpace(Span),
    RepeatedAttribute(Span),
    UnknownAttribute(Span),
    UnknownBuiltin(Span),
    UnknownAccess(Span),
    UnknownIdent(Span, &'a str),
    UnknownScalarType(Span),
    UnknownType(Span),
    UnknownStorageFormat(Span),
    UnknownConservativeDepth(Span),
    UnknownEnableExtension(Span, &'a str),
    UnknownLanguageExtension(Span, &'a str),
    UnknownDiagnosticRuleName(Span),
    SizeAttributeTooLow(Span, u32),
    AlignAttributeTooLow(Span, Alignment),
    NonPowerOfTwoAlignAttribute(Span),
    InconsistentBinding(Span),
    TypeNotConstructible(Span),
    TypeNotInferable(Span),
    InitializationTypeMismatch {
        name: Span,
        expected: Box<str>,
        got: Box<str>,
    },
    DeclMissingTypeAndInit(Span),
    MissingAttribute(&'static str, Span),
    InvalidAtomicPointer(Span),
    InvalidAtomicOperandType(Span),
    InvalidRayQueryPointer(Span),
    Pointer(&'static str, Span),
    NotPointer(Span),
    NotReference(&'static str, Span),
    InvalidAssignment {
        span: Span,
        ty: InvalidAssignmentType,
    },
    ReservedKeyword(Span),
    /// Redefinition of an identifier (used for both module-scope and local redefinitions).
    Redefinition {
        /// Span of the identifier in the previous definition.
        previous: Span,

        /// Span of the identifier in the new definition.
        current: Span,
    },
    /// A declaration refers to itself directly.
    RecursiveDeclaration {
        /// The location of the name of the declaration.
        ident: Span,

        /// The point at which it is used.
        usage: Span,
    },
    /// A declaration refers to itself indirectly, through one or more other
    /// definitions.
    CyclicDeclaration {
        /// The location of the name of some declaration in the cycle.
        ident: Span,

        /// The edges of the cycle of references.
        ///
        /// Each `(decl, reference)` pair indicates that the declaration whose
        /// name is `decl` has an identifier at `reference` whose definition is
        /// the next declaration in the cycle. The last pair's `reference` is
        /// the same identifier as `ident`, above.
        path: Box<[(Span, Span)]>,
    },
    InvalidSwitchValue {
        uint: bool,
        span: Span,
    },
    CalledEntryPoint(Span),
    WrongArgumentCount {
        span: Span,
        expected: Range<u32>,
        found: u32,
    },
    FunctionReturnsVoid(Span),
    InvalidWorkGroupUniformLoad(Span),
    Internal(&'static str),
    ExpectedConstExprConcreteIntegerScalar(Span),
    ExpectedNonNegative(Span),
    ExpectedPositiveArrayLength(Span),
    MissingWorkgroupSize(Span),
    ConstantEvaluatorError(Box<ConstantEvaluatorError>, Span),
    AutoConversion(Box<AutoConversionError>),
    AutoConversionLeafScalar(Box<AutoConversionLeafScalarError>),
    ConcretizationFailed(Box<ConcretizationFailedError>),
    ExceededLimitForNestedBraces {
        span: Span,
        limit: u8,
    },
    PipelineConstantIDValue(Span),
    NotBool(Span),
    ConstAssertFailed(Span),
    DirectiveAfterFirstGlobalDecl {
        directive_span: Span,
    },
    EnableExtensionNotYetImplemented {
        kind: UnimplementedEnableExtension,
        span: Span,
    },
    EnableExtensionNotEnabled {
        kind: EnableExtension,
        span: Span,
    },
    LanguageExtensionNotYetImplemented {
        kind: UnimplementedLanguageExtension,
        span: Span,
    },
    DiagnosticInvalidSeverity {
        severity_control_name_span: Span,
    },
    DiagnosticDuplicateTriggeringRule(ConflictingDiagnosticRuleError),
    DiagnosticAttributeNotYetImplementedAtParseSite {
        site_name_plural: &'static str,
        spans: Vec<Span>,
    },
    DiagnosticAttributeNotSupported {
        on_what: DiagnosticAttributeNotSupportedPosition,
        spans: Vec<Span>,
    },
}

impl From<ConflictingDiagnosticRuleError> for Error<'_> {
    fn from(value: ConflictingDiagnosticRuleError) -> Self {
        Self::DiagnosticDuplicateTriggeringRule(value)
    }
}

/// Used for diagnostic refinement in [`Error::DiagnosticAttributeNotSupported`].
#[derive(Clone, Copy, Debug)]
pub(crate) enum DiagnosticAttributeNotSupportedPosition {
    SemicolonInModulePosition,
    Other { display_plural: &'static str },
}

impl From<&'static str> for DiagnosticAttributeNotSupportedPosition {
    fn from(display_plural: &'static str) -> Self {
        Self::Other { display_plural }
    }
}

#[derive(Clone, Debug)]
pub(crate) struct AutoConversionError {
    pub dest_span: Span,
    pub dest_type: Box<str>,
    pub source_span: Span,
    pub source_type: Box<str>,
}

#[derive(Clone, Debug)]
pub(crate) struct AutoConversionLeafScalarError {
    pub dest_span: Span,
    pub dest_scalar: Box<str>,
    pub source_span: Span,
    pub source_type: Box<str>,
}

#[derive(Clone, Debug)]
pub(crate) struct ConcretizationFailedError {
    pub expr_span: Span,
    pub expr_type: Box<str>,
    pub scalar: Box<str>,
    pub inner: ConstantEvaluatorError,
}

impl<'a> Error<'a> {
    #[cold]
    #[inline(never)]
    pub(crate) fn as_parse_error(&self, source: &'a str) -> ParseError {
        match *self {
            Error::Unexpected(unexpected_span, expected) => {
                let expected_str = match expected {
                    ExpectedToken::Token(token) => match token {
                        Token::Separator(c) => format!("'{c}'"),
                        Token::Paren(c) => format!("'{c}'"),
                        Token::Attribute => "@".to_string(),
                        Token::Number(_) => "number".to_string(),
                        Token::Word(s) => s.to_string(),
                        Token::Operation(c) => format!("operation ('{c}')"),
                        Token::LogicalOperation(c) => format!("logical operation ('{c}')"),
                        Token::ShiftOperation(c) => format!("bitshift ('{c}{c}')"),
                        Token::AssignmentOperation(c) if c == '<' || c == '>' => {
                            format!("bitshift ('{c}{c}=')")
                        }
                        Token::AssignmentOperation(c) => format!("operation ('{c}=')"),
                        Token::IncrementOperation => "increment operation".to_string(),
                        Token::DecrementOperation => "decrement operation".to_string(),
                        Token::Arrow => "->".to_string(),
                        Token::Unknown(c) => format!("unknown ('{c}')"),
                        Token::Trivia => "trivia".to_string(),
                        Token::End => "end".to_string(),
                    },
                    ExpectedToken::Identifier => "identifier".to_string(),
                    ExpectedToken::PrimaryExpression => "expression".to_string(),
                    ExpectedToken::Assignment => "assignment or increment/decrement".to_string(),
                    ExpectedToken::SwitchItem => concat!(
                        "switch item ('case' or 'default') or a closing curly bracket ",
                        "to signify the end of the switch statement ('}')"
                    )
                    .to_string(),
                    ExpectedToken::WorkgroupSizeSeparator => {
                        "workgroup size separator (',') or a closing parenthesis".to_string()
                    }
                    ExpectedToken::GlobalItem => concat!(
                        "global item ('struct', 'const', 'var', 'alias', ';', 'fn') ",
                        "or the end of the file"
                    )
                    .to_string(),
                    ExpectedToken::Type => "type".to_string(),
                    ExpectedToken::Variable => "variable access".to_string(),
                    ExpectedToken::Function => "function name".to_string(),
                    ExpectedToken::AfterIdentListArg => {
                        "next argument, trailing comma, or end of list (',' or ';')".to_string()
                    }
                    ExpectedToken::AfterIdentListComma => {
                        "next argument or end of list (';')".to_string()
                    }
                    ExpectedToken::DiagnosticAttribute => {
                        "the 'diagnostic' attribute identifier".to_string()
                    }
                };
                ParseError {
                    message: format!(
                        "expected {}, found '{}'",
                        expected_str, &source[unexpected_span],
                    ),
                    labels: vec![(unexpected_span, format!("expected {expected_str}").into())],
                    notes: vec![],
                }
            }
            Error::UnexpectedComponents(bad_span) => ParseError {
                message: "unexpected components".to_string(),
                labels: vec![(bad_span, "unexpected components".into())],
                notes: vec![],
            },
            Error::UnexpectedOperationInConstContext(span) => ParseError {
                message: "this operation is not supported in a const context".to_string(),
                labels: vec![(span, "operation not supported here".into())],
                notes: vec![],
            },
            Error::BadNumber(bad_span, ref err) => ParseError {
                message: format!("{}: `{}`", err, &source[bad_span],),
                labels: vec![(bad_span, err.to_string().into())],
                notes: vec![],
            },
            Error::BadMatrixScalarKind(span, scalar) => ParseError {
                message: format!(
                    "matrix scalar type must be floating-point, but found `{}`",
                    scalar.to_wgsl()
                ),
                labels: vec![(span, "must be floating-point (e.g. `f32`)".into())],
                notes: vec![],
            },
            Error::BadAccessor(accessor_span) => ParseError {
                message: format!("invalid field accessor `{}`", &source[accessor_span],),
                labels: vec![(accessor_span, "invalid accessor".into())],
                notes: vec![],
            },
            Error::UnknownIdent(ident_span, ident) => ParseError {
                message: format!("no definition in scope for identifier: '{ident}'"),
                labels: vec![(ident_span, "unknown identifier".into())],
                notes: vec![],
            },
            Error::UnknownScalarType(bad_span) => ParseError {
                message: format!("unknown scalar type: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown scalar type".into())],
                notes: vec!["Valid scalar types are f32, f64, i32, u32, bool".into()],
            },
            Error::BadTextureSampleType { span, scalar } => ParseError {
                message: format!(
                    "texture sample type must be one of f32, i32 or u32, but found {}",
                    scalar.to_wgsl()
                ),
                labels: vec![(span, "must be one of f32, i32 or u32".into())],
                notes: vec![],
            },
            Error::BadIncrDecrReferenceType(span) => ParseError {
                message: concat!(
                    "increment/decrement operation requires ",
                    "reference type to be one of i32 or u32"
                )
                .to_string(),
                labels: vec![(span, "must be a reference type of i32 or u32".into())],
                notes: vec![],
            },
            Error::BadTexture(bad_span) => ParseError {
                message: format!(
                    "expected an image, but found '{}' which is not an image",
                    &source[bad_span]
                ),
                labels: vec![(bad_span, "not an image".into())],
                notes: vec![],
            },
            Error::BadTypeCast {
                span,
                ref from_type,
                ref to_type,
            } => {
                let msg = format!("cannot cast a {from_type} to a {to_type}");
                ParseError {
                    message: msg.clone(),
                    labels: vec![(span, msg.into())],
                    notes: vec![],
                }
            }
            Error::InvalidResolve(ref resolve_error) => ParseError {
                message: resolve_error.to_string(),
                labels: vec![],
                notes: vec![],
            },
            Error::InvalidForInitializer(bad_span) => ParseError {
                message: format!(
                    "for(;;) initializer is not an assignment or a function call: '{}'",
                    &source[bad_span]
                ),
                labels: vec![(bad_span, "not an assignment or function call".into())],
                notes: vec![],
            },
            Error::InvalidBreakIf(bad_span) => ParseError {
                message: "A break if is only allowed in a continuing block".to_string(),
                labels: vec![(bad_span, "not in a continuing block".into())],
                notes: vec![],
            },
            Error::InvalidGatherComponent(bad_span) => ParseError {
                message: format!(
                    "textureGather component '{}' doesn't exist, must be 0, 1, 2, or 3",
                    &source[bad_span]
                ),
                labels: vec![(bad_span, "invalid component".into())],
                notes: vec![],
            },
            Error::InvalidConstructorComponentType(bad_span, component) => ParseError {
                message: format!("invalid type for constructor component at index [{component}]"),
                labels: vec![(bad_span, "invalid component type".into())],
                notes: vec![],
            },
            Error::InvalidIdentifierUnderscore(bad_span) => ParseError {
                message: "Identifier can't be '_'".to_string(),
                labels: vec![(bad_span, "invalid identifier".into())],
                notes: vec![
                    "Use phony assignment instead ('_ =' notice the absence of 'let' or 'var')"
                        .to_string(),
                ],
            },
            Error::ReservedIdentifierPrefix(bad_span) => ParseError {
                message: format!(
                    "Identifier starts with a reserved prefix: '{}'",
                    &source[bad_span]
                ),
                labels: vec![(bad_span, "invalid identifier".into())],
                notes: vec![],
            },
            Error::UnknownAddressSpace(bad_span) => ParseError {
                message: format!("unknown address space: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown address space".into())],
                notes: vec![],
            },
            Error::RepeatedAttribute(bad_span) => ParseError {
                message: format!("repeated attribute: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "repeated attribute".into())],
                notes: vec![],
            },
            Error::UnknownAttribute(bad_span) => ParseError {
                message: format!("unknown attribute: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown attribute".into())],
                notes: vec![],
            },
            Error::UnknownBuiltin(bad_span) => ParseError {
                message: format!("unknown builtin: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown builtin".into())],
                notes: vec![],
            },
            Error::UnknownAccess(bad_span) => ParseError {
                message: format!("unknown access: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown access".into())],
                notes: vec![],
            },
            Error::UnknownStorageFormat(bad_span) => ParseError {
                message: format!("unknown storage format: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown storage format".into())],
                notes: vec![],
            },
            Error::UnknownConservativeDepth(bad_span) => ParseError {
                message: format!("unknown conservative depth: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown conservative depth".into())],
                notes: vec![],
            },
            Error::UnknownType(bad_span) => ParseError {
                message: format!("unknown type: '{}'", &source[bad_span]),
                labels: vec![(bad_span, "unknown type".into())],
                notes: vec![],
            },
            Error::UnknownEnableExtension(span, word) => ParseError {
                message: format!("unknown enable-extension `{}`", word),
                labels: vec![(span, "".into())],
                notes: vec![
                    "See available extensions at <https://www.w3.org/TR/WGSL/#enable-extension>."
                        .into(),
                ],
            },
            Error::UnknownLanguageExtension(span, name) => ParseError {
                message: format!("unknown language extension `{name}`"),
                labels: vec![(span, "".into())],
                notes: vec![concat!(
                    "See available extensions at ",
                    "<https://www.w3.org/TR/WGSL/#language-extensions-sec>."
                )
                .into()],
            },
            Error::UnknownDiagnosticRuleName(span) => ParseError {
                message: format!("unknown `diagnostic(…)` rule name `{}`", &source[span]),
                labels: vec![(span, "not a valid diagnostic rule name".into())],
                notes: vec![concat!(
                    "See available trigger rules at ",
                    "<https://www.w3.org/TR/WGSL/#filterable-triggering-rules>."
                )
                .into()],
            },
            Error::SizeAttributeTooLow(bad_span, min_size) => ParseError {
                message: format!("struct member size must be at least {min_size}"),
                labels: vec![(bad_span, format!("must be at least {min_size}").into())],
                notes: vec![],
            },
            Error::AlignAttributeTooLow(bad_span, min_align) => ParseError {
                message: format!("struct member alignment must be at least {min_align}"),
                labels: vec![(bad_span, format!("must be at least {min_align}").into())],
                notes: vec![],
            },
            Error::NonPowerOfTwoAlignAttribute(bad_span) => ParseError {
                message: "struct member alignment must be a power of 2".to_string(),
                labels: vec![(bad_span, "must be a power of 2".into())],
                notes: vec![],
            },
            Error::InconsistentBinding(span) => ParseError {
                message: "input/output binding is not consistent".to_string(),
                labels: vec![(span, "input/output binding is not consistent".into())],
                notes: vec![],
            },
            Error::TypeNotConstructible(span) => ParseError {
                message: format!("type `{}` is not constructible", &source[span]),
                labels: vec![(span, "type is not constructible".into())],
                notes: vec![],
            },
            Error::TypeNotInferable(span) => ParseError {
                message: "type can't be inferred".to_string(),
                labels: vec![(span, "type can't be inferred".into())],
                notes: vec![],
            },
            Error::InitializationTypeMismatch {
                name,
                ref expected,
                ref got,
            } => ParseError {
                message: format!(
                    "the type of `{}` is expected to be `{}`, but got `{}`",
                    &source[name], expected, got,
                ),
                labels: vec![(name, format!("definition of `{}`", &source[name]).into())],
                notes: vec![],
            },
            Error::DeclMissingTypeAndInit(name_span) => ParseError {
                message: format!(
                    "declaration of `{}` needs a type specifier or initializer",
                    &source[name_span]
                ),
                labels: vec![(name_span, "needs a type specifier or initializer".into())],
                notes: vec![],
            },
            Error::MissingAttribute(name, name_span) => ParseError {
                message: format!(
                    "variable `{}` needs a '{}' attribute",
                    &source[name_span], name
                ),
                labels: vec![(
                    name_span,
                    format!("definition of `{}`", &source[name_span]).into(),
                )],
                notes: vec![],
            },
            Error::InvalidAtomicPointer(span) => ParseError {
                message: "atomic operation is done on a pointer to a non-atomic".to_string(),
                labels: vec![(span, "atomic pointer is invalid".into())],
                notes: vec![],
            },
            Error::InvalidAtomicOperandType(span) => ParseError {
                message: "atomic operand type is inconsistent with the operation".to_string(),
                labels: vec![(span, "atomic operand type is invalid".into())],
                notes: vec![],
            },
            Error::InvalidRayQueryPointer(span) => ParseError {
                message: "ray query operation is done on a pointer to a non-ray-query".to_string(),
                labels: vec![(span, "ray query pointer is invalid".into())],
                notes: vec![],
            },
            Error::NotPointer(span) => ParseError {
                message: "the operand of the `*` operator must be a pointer".to_string(),
                labels: vec![(span, "expression is not a pointer".into())],
                notes: vec![],
            },
            Error::NotReference(what, span) => ParseError {
                message: format!("{what} must be a reference"),
                labels: vec![(span, "expression is not a reference".into())],
                notes: vec![],
            },
            Error::InvalidAssignment { span, ty } => {
                let (extra_label, notes) = match ty {
                    InvalidAssignmentType::Swizzle => (
                        None,
                        vec![
                            "WGSL does not support assignments to swizzles".into(),
                            "consider assigning each component individually".into(),
                        ],
                    ),
                    InvalidAssignmentType::ImmutableBinding(binding_span) => (
                        Some((binding_span, "this is an immutable binding".into())),
                        vec![format!(
                            "consider declaring '{}' with `var` instead of `let`",
                            &source[binding_span]
                        )],
                    ),
                    InvalidAssignmentType::Other => (None, vec![]),
                };

                ParseError {
                    message: "invalid left-hand side of assignment".into(),
                    labels: std::iter::once((span, "cannot assign to this expression".into()))
                        .chain(extra_label)
                        .collect(),
                    notes,
                }
            }
            Error::Pointer(what, span) => ParseError {
                message: format!("{what} must not be a pointer"),
                labels: vec![(span, "expression is a pointer".into())],
                notes: vec![],
            },
            Error::ReservedKeyword(name_span) => ParseError {
                message: format!("name `{}` is a reserved keyword", &source[name_span]),
                labels: vec![(
                    name_span,
                    format!("definition of `{}`", &source[name_span]).into(),
                )],
                notes: vec![],
            },
            Error::Redefinition { previous, current } => ParseError {
                message: format!("redefinition of `{}`", &source[current]),
                labels: vec![
                    (
                        current,
                        format!("redefinition of `{}`", &source[current]).into(),
                    ),
                    (
                        previous,
                        format!("previous definition of `{}`", &source[previous]).into(),
                    ),
                ],
                notes: vec![],
            },
            Error::RecursiveDeclaration { ident, usage } => ParseError {
                message: format!("declaration of `{}` is recursive", &source[ident]),
                labels: vec![(ident, "".into()), (usage, "uses itself here".into())],
                notes: vec![],
            },
            Error::CyclicDeclaration { ident, ref path } => ParseError {
                message: format!("declaration of `{}` is cyclic", &source[ident]),
                labels: path
                    .iter()
                    .enumerate()
                    .flat_map(|(i, &(ident, usage))| {
                        [
                            (ident, "".into()),
                            (
                                usage,
                                if i == path.len() - 1 {
                                    "ending the cycle".into()
                                } else {
                                    format!("uses `{}`", &source[ident]).into()
                                },
                            ),
                        ]
                    })
                    .collect(),
                notes: vec![],
            },
            Error::InvalidSwitchValue { uint, span } => ParseError {
                message: "invalid switch value".to_string(),
                labels: vec![(
                    span,
                    if uint {
                        "expected unsigned integer"
                    } else {
                        "expected signed integer"
                    }
                    .into(),
                )],
                notes: vec![if uint {
                    format!("suffix the integer with a `u`: '{}u'", &source[span])
                } else {
                    let span = span.to_range().unwrap();
                    format!(
                        "remove the `u` suffix: '{}'",
                        &source[span.start..span.end - 1]
                    )
                }],
            },
            Error::CalledEntryPoint(span) => ParseError {
                message: "entry point cannot be called".to_string(),
                labels: vec![(span, "entry point cannot be called".into())],
                notes: vec![],
            },
            Error::WrongArgumentCount {
                span,
                ref expected,
                found,
            } => ParseError {
                message: format!(
                    "wrong number of arguments: expected {}, found {}",
                    if expected.len() < 2 {
                        format!("{}", expected.start)
                    } else {
                        format!("{}..{}", expected.start, expected.end)
                    },
                    found
                ),
                labels: vec![(span, "wrong number of arguments".into())],
                notes: vec![],
            },
            Error::FunctionReturnsVoid(span) => ParseError {
                message: "function does not return any value".to_string(),
                labels: vec![(span, "".into())],
                notes: vec![
                    "perhaps you meant to call the function in a separate statement?".into(),
                ],
            },
            Error::InvalidWorkGroupUniformLoad(span) => ParseError {
                message: "incorrect type passed to workgroupUniformLoad".into(),
                labels: vec![(span, "".into())],
                notes: vec!["passed type must be a workgroup pointer".into()],
            },
            Error::Internal(message) => ParseError {
                message: "internal WGSL front end error".to_string(),
                labels: vec![],
                notes: vec![message.into()],
            },
            Error::ExpectedConstExprConcreteIntegerScalar(span) => ParseError {
                message: concat!(
                    "must be a const-expression that ",
                    "resolves to a concrete integer scalar (u32 or i32)"
                )
                .to_string(),
                labels: vec![(span, "must resolve to u32 or i32".into())],
                notes: vec![],
            },
            Error::ExpectedNonNegative(span) => ParseError {
                message: "must be non-negative (>= 0)".to_string(),
                labels: vec![(span, "must be non-negative".into())],
                notes: vec![],
            },
            Error::ExpectedPositiveArrayLength(span) => ParseError {
                message: "array element count must be positive (> 0)".to_string(),
                labels: vec![(span, "must be positive".into())],
                notes: vec![],
            },
            Error::ConstantEvaluatorError(ref e, span) => ParseError {
                message: e.to_string(),
                labels: vec![(span, "see msg".into())],
                notes: vec![],
            },
            Error::MissingWorkgroupSize(span) => ParseError {
                message: "workgroup size is missing on compute shader entry point".to_string(),
                labels: vec![(
                    span,
                    "must be paired with a @workgroup_size attribute".into(),
                )],
                notes: vec![],
            },
            Error::AutoConversion(ref error) => {
                // destructuring ensures all fields are handled
                let AutoConversionError {
                    dest_span,
                    ref dest_type,
                    source_span,
                    ref source_type,
                } = **error;
                ParseError {
                    message: format!(
                        "automatic conversions cannot convert `{}` to `{}`",
                        source_type, dest_type
                    ),
                    labels: vec![
                        (
                            dest_span,
                            format!("a value of type {dest_type} is required here").into(),
                        ),
                        (
                            source_span,
                            format!("this expression has type {source_type}").into(),
                        ),
                    ],
                    notes: vec![],
                }
            }
            Error::AutoConversionLeafScalar(ref error) => {
                let AutoConversionLeafScalarError {
                    dest_span,
                    ref dest_scalar,
                    source_span,
                    ref source_type,
                } = **error;
                ParseError {
                    message: format!(
                        "automatic conversions cannot convert elements of `{}` to `{}`",
                        source_type, dest_scalar
                    ),
                    labels: vec![
                        (
                            dest_span,
                            format!(
                                "a value with elements of type {} is required here",
                                dest_scalar
                            )
                            .into(),
                        ),
                        (
                            source_span,
                            format!("this expression has type {source_type}").into(),
                        ),
                    ],
                    notes: vec![],
                }
            }
            Error::ConcretizationFailed(ref error) => {
                let ConcretizationFailedError {
                    expr_span,
                    ref expr_type,
                    ref scalar,
                    ref inner,
                } = **error;
                ParseError {
                    message: format!("failed to convert expression to a concrete type: {inner}"),
                    labels: vec![(
                        expr_span,
                        format!("this expression has type {expr_type}").into(),
                    )],
                    notes: vec![format!(
                        "the expression should have been converted to have {} scalar type",
                        scalar
                    )],
                }
            }
            Error::ExceededLimitForNestedBraces { span, limit } => ParseError {
                message: "brace nesting limit reached".into(),
                labels: vec![(span, "limit reached at this brace".into())],
                notes: vec![format!("nesting limit is currently set to {limit}")],
            },
            Error::PipelineConstantIDValue(span) => ParseError {
                message: "pipeline constant ID must be between 0 and 65535 inclusive".to_string(),
                labels: vec![(span, "must be between 0 and 65535 inclusive".into())],
                notes: vec![],
            },
            Error::NotBool(span) => ParseError {
                message: "must be a const-expression that resolves to a bool".to_string(),
                labels: vec![(span, "must resolve to bool".into())],
                notes: vec![],
            },
            Error::ConstAssertFailed(span) => ParseError {
                message: "const_assert failure".to_string(),
                labels: vec![(span, "evaluates to false".into())],
                notes: vec![],
            },
            Error::DirectiveAfterFirstGlobalDecl { directive_span } => ParseError {
                message: "expected global declaration, but found a global directive".into(),
                labels: vec![(
                    directive_span,
                    "written after first global declaration".into(),
                )],
                notes: vec![concat!(
                    "global directives are only allowed before global declarations; ",
                    "maybe hoist this closer to the top of the shader module?"
                )
                .into()],
            },
            Error::EnableExtensionNotYetImplemented { kind, span } => ParseError {
                message: format!(
                    "the `{}` enable-extension is not yet supported",
                    EnableExtension::Unimplemented(kind).to_ident()
                ),
                labels: vec![(
                    span,
                    concat!(
                        "this enable-extension specifies standard functionality ",
                        "which is not yet implemented in Naga"
                    )
                    .into(),
                )],
                notes: vec![format!(
                    concat!(
                        "Let Naga maintainers know that you ran into this at ",
                        "<https://github.com/gfx-rs/wgpu/issues/{}>, ",
                        "so they can prioritize it!"
                    ),
                    kind.tracking_issue_num()
                )],
            },
            Error::EnableExtensionNotEnabled { kind, span } => ParseError {
                message: format!("`{}` enable-extension is not enabled", kind.to_ident()),
                labels: vec![(
                    span,
                    format!(
                        concat!(
                            "the `{}` enable-extension is needed for this functionality, ",
                            "but it is not currently enabled"
                        ),
                        kind.to_ident()
                    )
                    .into(),
                )],
                #[allow(irrefutable_let_patterns)]
                notes: if let EnableExtension::Unimplemented(kind) = kind {
                    vec![format!(
                        concat!(
                            "This enable-extension is not yet implemented. ",
                            "Let Naga maintainers know that you ran into this at ",
                            "<https://github.com/gfx-rs/wgpu/issues/{}>, ",
                            "so they can prioritize it!"
                        ),
                        kind.tracking_issue_num()
                    )]
                } else {
                    vec![]
                },
            },
            Error::LanguageExtensionNotYetImplemented { kind, span } => ParseError {
                message: format!(
                    "the `{}` language extension is not yet supported",
                    LanguageExtension::Unimplemented(kind).to_ident()
                ),
                labels: vec![(span, "".into())],
                notes: vec![format!(
                    concat!(
                        "Let Naga maintainers know that you ran into this at ",
                        "<https://github.com/gfx-rs/wgpu/issues/{}>, ",
                        "so they can prioritize it!"
                    ),
                    kind.tracking_issue_num()
                )],
            },
            Error::DiagnosticInvalidSeverity {
                severity_control_name_span,
            } => ParseError {
                message: "invalid `diagnostic(…)` severity".into(),
                labels: vec![(
                    severity_control_name_span,
                    "not a valid severity level".into(),
                )],
                notes: vec![concat!(
                    "See available severities at ",
                    "<https://www.w3.org/TR/WGSL/#diagnostic-severity>."
                )
                .into()],
            },
            Error::DiagnosticDuplicateTriggeringRule(ConflictingDiagnosticRuleError {
                triggering_rule_spans,
            }) => {
                let [first_span, second_span] = triggering_rule_spans;
                ParseError {
                    message: "found conflicting `diagnostic(…)` rule(s)".into(),
                    labels: vec![
                        (first_span, "first rule".into()),
                        (second_span, "second rule".into()),
                    ],
                    notes: vec![
                        concat!(
                            "Multiple `diagnostic(…)` rules with the same rule name ",
                            "conflict unless they are directives and the severity is the same.",
                        )
                        .into(),
                        "You should delete the rule you don't want.".into(),
                    ],
                }
            }
            Error::DiagnosticAttributeNotYetImplementedAtParseSite {
                site_name_plural,
                ref spans,
            } => ParseError {
                message: "`@diagnostic(…)` attribute(s) not yet implemented".into(),
                labels: {
                    let mut spans = spans.iter().cloned();
                    let first = spans
                        .next()
                        .map(|span| {
                            (
                                span,
                                format!("can't use this on {site_name_plural} (yet)").into(),
                            )
                        })
                        .expect("internal error: diag. attr. rejection on empty map");
                    std::iter::once(first)
                        .chain(spans.map(|span| (span, "".into())))
                        .collect()
                },
                notes: vec![format!(concat!(
                    "Let Naga maintainers know that you ran into this at ",
                    "<https://github.com/gfx-rs/wgpu/issues/5320>, ",
                    "so they can prioritize it!"
                ))],
            },
            Error::DiagnosticAttributeNotSupported { on_what, ref spans } => {
                // In this case the user may have intended to create a global diagnostic filter directive,
                // so display a note to them suggesting the correct syntax.
                let intended_diagnostic_directive = match on_what {
                    DiagnosticAttributeNotSupportedPosition::SemicolonInModulePosition => true,
                    DiagnosticAttributeNotSupportedPosition::Other { .. } => false,
                };
                let on_what_plural = match on_what {
                    DiagnosticAttributeNotSupportedPosition::SemicolonInModulePosition => {
                        "semicolons"
                    }
                    DiagnosticAttributeNotSupportedPosition::Other { display_plural } => {
                        display_plural
                    }
                };
                ParseError {
                    message: format!(
                        "`@diagnostic(…)` attribute(s) on {on_what_plural} are not supported",
                    ),
                    labels: spans
                        .iter()
                        .cloned()
                        .map(|span| (span, "".into()))
                        .collect(),
                    notes: vec![
                        concat!(
                            "`@diagnostic(…)` attributes are only permitted on `fn`s, ",
                            "some statements, and `switch`/`loop` bodies."
                        )
                        .into(),
                        {
                            if intended_diagnostic_directive {
                                concat!(
                                    "If you meant to declare a diagnostic filter that ",
                                    "applies to the entire module, move this line to ",
                                    "the top of the file and remove the `@` symbol."
                                )
                                .into()
                            } else {
                                concat!(
                                    "These attributes are well-formed, ",
                                    "you likely just need to move them."
                                )
                                .into()
                            }
                        },
                    ],
                }
            }
        }
    }
}

#[test]
fn test_error_size() {
    assert!(size_of::<Error<'_>>() <= 48);
}