hcl/

macros.rs

/// Construct an `hcl::Body` from HCL blocks and attributes.
///
/// The macro supports a subset of the HCL syntax. If you need more flexibility, use the
/// [`BlockBuilder`][crate::structure::BlockBuilder] instead.
///
/// # Supported Syntax
///
/// - Attribute keys and block identifiers can be raw identifiers (`identifier`) or parenthesized
///   expressions (`(expr)`).
/// - Block labels can be string literals (`"label"`), identifiers (`label`) or parenthesized
///   expressions (`(label_expr)`).
/// - Object keys can be string literals (`"key"`), identifiers (`key`) or parenthesized
///   expressions (`(key_expr)`).
/// - Attribute expression values can be any valid primitive, collection or expression.
///
/// # Unsupported syntax
///
/// Heredocs are not supported by the `hcl::body` macro.
///
/// # Related macros
///
/// The `body!` macro is composed out of different other macros that can be used on their own to
/// construct HCL data structures:
///
/// - [`attribute!`][`crate::attribute!`]: constructs an [`Attribute`][crate::structure::Attribute]
/// - [`block!`][`crate::block!`]: constructs a [`Block`][crate::structure::Block]
/// - [`expression!`][`crate::expression!`]: constructs an [`Expression`][crate::expr::Expression]
/// - [`structure!`][`crate::structure!`]: constructs a [`Structure`][crate::structure::Structure]
///
/// Additionally the [`value!`][`crate::value!`] macro is provided for constructing a
/// [`Value`][crate::value::Value].
///
/// # Example
///
/// ```
/// use hcl::{Block, Body};
///
/// let body = hcl::body!({
///     resource "aws_sns_topic" "topic" {
///         name = "my-topic"
///     }
/// });
///
/// let expected = Body::builder()
///     .add_block(
///         Block::builder("resource")
///             .add_label("aws_sns_topic")
///             .add_label("topic")
///             .add_attribute(("name", "my-topic"))
///             .build()
///     )
///     .build();
///
/// assert_eq!(body, expected);
/// ```
///
/// Attribute keys, block identifiers and object keys can be expressions by wrapping them in
/// parenthesis:
///
/// ```
/// use hcl::{Block, Body};
///
/// let block_identifier = "resource";
/// let attribute_key = "name";
///
/// let body = hcl::body!({
///     (block_identifier) "aws_sns_topic" "topic" {
///         (attribute_key) = "my-topic"
///     }
/// });
///
/// let expected = Body::builder()
///     .add_block(
///         Block::builder(block_identifier)
///             .add_label("aws_sns_topic")
///             .add_label("topic")
///             .add_attribute((attribute_key, "my-topic"))
///             .build()
///     )
///     .build();
///
/// assert_eq!(body, expected);
/// ```
#[macro_export]
macro_rules! body {
    // Hide distracting implementation details from the generated rustdoc.
    ($($body:tt)*) => {
        $crate::body_internal!($($body)*)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! body_internal {
    //////////////////////////////////////////////////////////////////////////
    // TT muncher for parsing zero or more HCL structures (attributes and blocks).
    //
    // Produces a vec![...] of the elements.
    //
    // Must be invoked as: body_internal!(@structures [] $($tt)*)
    //////////////////////////////////////////////////////////////////////////

    // No tokens left, done.
    (@structures [$(($elems:expr))*]) => {
        std::vec![$($elems),*]
    };

    // Next element is an attribute, munch into elems and proceed with next structure.
    (@structures [$(($elems:expr))*] $key:tt = $expr:tt $($rest:tt)*) => {
        $crate::body_internal!(@structures [$(($elems))* ($crate::structure!($key = $expr))] $($rest)*)
    };

    // Next element must be a block, invoke block muncher.
    (@structures [$(($elems:expr))*] $ident:tt $($rest:tt)+) => {
        $crate::body_internal!(@block [$(($elems))*] $ident $($rest)+)
    };

    //////////////////////////////////////////////////////////////////////////
    // TT muncher for parsing an HCL block.
    //
    // Must be invoked as: body_internal!(@block [$(($elems))*] $ident $($rest)+)
    //////////////////////////////////////////////////////////////////////////

    // Found block body, munch block into elems and proceed with next structure.
    (@block [$(($elems:expr))*] ($ident:expr) [$(($labels:expr))*] { $($body:tt)* } $($rest:tt)*) => {
        $crate::body_internal!(@structures [$(($elems))* ($crate::structure!(($ident) [$(($labels))*] { $($body)* }))] $($rest)*)
    };

    // Munch an identifier block label.
    (@block [$(($elems:expr))*] ($ident:expr) [$(($labels:expr))*] $label:ident $($rest:tt)+) => {
        $crate::body_internal!(@block [$(($elems))*] ($ident) [$(($labels))* ($crate::block_label!($label))] $($rest)+)
    };

    // Munch a literal expression block label.
    (@block [$(($elems:expr))*] ($ident:expr) [$(($labels:expr))*] $label:literal $($rest:tt)+) => {
        $crate::body_internal!(@block [$(($elems))*] ($ident) [$(($labels))* ($crate::block_label!($label))] $($rest)+)
    };

    // Munch an expression block label.
    (@block [$(($elems:expr))*] ($ident:expr) [$(($labels:expr))*] ($label:expr) $($rest:tt)+) => {
        $crate::body_internal!(@block [$(($elems))*] ($ident) [$(($labels))* ($crate::block_label!(($label)))] $($rest)+)
    };

    // Block with identifier.
    (@block [$(($elems:expr))*] $ident:ident $($rest:tt)+) => {
        $crate::body_internal!(@block [$(($elems))*] (std::stringify!($ident)) [] $($rest)+)
    };

    // Block with expression as identifier.
    (@block [$(($elems:expr))*] ($ident:expr) $($rest:tt)+) => {
        $crate::body_internal!(@block [$(($elems))*] ($ident) [] $($rest)+)
    };

    //////////////////////////////////////////////////////////////////////////
    // The main implementation.
    //
    // Must be invoked as: body_internal!($($tt)+)
    //////////////////////////////////////////////////////////////////////////

    // Body in curly braces.
    ({ $($tt:tt)* }) => {
        $crate::body_internal!($($tt)*)
    };

    // Invoke structure muncher.
    ($($tt:tt)*) => {
        $crate::structure::Body($crate::body_internal!(@structures [] $($tt)*))
    };
}

/// Construct an `hcl::Structure` which may be either an HCL attribute or block.
///
/// For supported syntax see the [`body!`] macro documentation.
///
/// # Example
///
/// ```
/// use hcl::{Attribute, Block, Structure};
///
/// assert_eq!(
///     hcl::structure!(foo = "bar"),
///     Structure::Attribute(Attribute::new("foo", "bar")),
/// );
///
/// assert_eq!(
///     hcl::structure!(
///         resource "aws_s3_bucket" "bucket" {
///             name = "the-bucket"
///         }
///     ),
///     Structure::Block(
///         Block::builder("resource")
///             .add_labels(["aws_s3_bucket", "bucket"])
///             .add_attribute(("name", "the-bucket"))
///             .build()
///     ),
/// );
/// ```
#[macro_export]
macro_rules! structure {
    // Hide distracting implementation details from the generated rustdoc.
    ($($structure:tt)+) => {
        $crate::structure_internal!($($structure)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! structure_internal {
    // Structure in braces.
    ({ $($structure:tt)+ }) => {
        $crate::structure_internal!($($structure)+)
    };

    // An attribute structure.
    ($key:tt = $($expr:tt)+) => {
        $crate::structure::Structure::Attribute($crate::attribute!($key = $($expr)+))
    };

    // A block structure.
    ($($block:tt)+) => {
        $crate::structure::Structure::Block($crate::block!($($block)+))
    };
}

/// Construct an `hcl::Attribute` from a key and a value expression.
///
/// For supported syntax see the [`body!`] macro documentation.
///
/// # Example
///
/// ```
/// use hcl::Attribute;
///
/// assert_eq!(hcl::attribute!(foo = "bar"), Attribute::new("foo", "bar"));
/// ```
#[macro_export]
macro_rules! attribute {
    // Hide distracting implementation details from the generated rustdoc.
    ($($attr:tt)+) => {
        $crate::attribute_internal!($($attr)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! attribute_internal {
    // Attribute in curly braces.
    ({ $($attribute:tt)+ }) => {
        $crate::attribute_internal!($($attribute)+)
    };

    // Attribute with expression as key.
    (($key:expr) = $($expr:tt)+) => {
        $crate::Attribute {
            key: ($key).into(),
            expr: $crate::expression_internal!($($expr)+),
        }
    };

    // Attribute with identifier as key.
    ($key:ident = $($expr:tt)+) => {
        $crate::attribute_internal!((std::stringify!($key)) = $($expr)+)
    };
}

/// Construct an `hcl::Block` from a block identifier, optional block labels and a block body.
///
/// For supported syntax see the [`body!`] macro documentation.
///
/// # Example
///
/// ```
/// use hcl::Block;
///
/// assert_eq!(
///     hcl::block!(
///         resource "aws_s3_bucket" "bucket" {
///             name = "the-bucket"
///         }
///     ),
///     Block::builder("resource")
///         .add_labels(["aws_s3_bucket", "bucket"])
///         .add_attribute(("name", "the-bucket"))
///         .build(),
/// );
/// ```
#[macro_export]
macro_rules! block {
    // Hide distracting implementation details from the generated rustdoc.
    ($($block:tt)+) => {
        $crate::block_internal!($($block)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! block_internal {
    // Block in curly braces.
    ({ $($block:tt)+ }) => {
        $crate::block_internal!($($block)+)
    };

    // Munch an identifier label.
    (($ident:expr) [$(($labels:expr))*] $label:ident $($rest:tt)+) => {
        $crate::block_internal!(($ident) [$(($labels))* ($crate::block_label!($label))] $($rest)+)
    };

    // Munch a literal expression label.
    (($ident:expr) [$(($labels:expr))*] $label:literal $($rest:tt)+) => {
        $crate::block_internal!(($ident) [$(($labels))* ($crate::block_label!($label))] $($rest)+)
    };

    // Munch an expression label.
    (($ident:expr) [$(($labels:expr))*] ($label:expr) $($rest:tt)+) => {
        $crate::block_internal!(($ident) [$(($labels))* ($crate::block_label!(($label)))] $($rest)+)
    };

    // Found block body, done.
    (($ident:expr) [$(($labels:expr))*] {$($body:tt)*}) => {
        $crate::Block {
            identifier: ($ident).into(),
            labels: std::vec![$($labels),*],
            body: $crate::body!($($body)*),
        }
    };

    // Munch expression as block identifier.
    (($ident:expr) $($rest:tt)+) => {
        $crate::block_internal!(($ident) [] $($rest)+)
    };

    // Munch normal block identifier.
    ($ident:ident $($rest:tt)+) => {
        $crate::block_internal!((std::stringify!($ident)) [] $($rest)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! block_label {
    ($ident:ident) => {
        $crate::structure::BlockLabel::Identifier($crate::Identifier::unchecked(std::stringify!(
            $ident
        )))
    };

    (($expr:expr)) => {
        $crate::structure::BlockLabel::String(($expr).into())
    };

    ($literal:literal) => {
        $crate::block_label!(($literal))
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! object_key {
    ($ident:ident) => {
        $crate::expr::ObjectKey::Identifier($crate::Identifier::unchecked(std::stringify!($ident)))
    };

    (($expr:expr)) => {
        $crate::expr::ObjectKey::Expression($crate::expression!($expr))
    };

    ($literal:literal) => {
        $crate::object_key!(($literal))
    };
}

/// Construct an `hcl::Expression` from an HCL attribute value expression literal.
///
/// For supported syntax see the [`body!`] macro documentation.
///
/// # Example
///
/// ```
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// use hcl::{Expression, Identifier, Object, ObjectKey};
///
/// let other = "hello";
///
/// let expression = hcl::expression!({
///     foo       = true
///     "baz qux" = [1, 2]
///     (other)   = "world"
/// });
///
/// let expected = Expression::Object(Object::from([
///     (ObjectKey::from(Identifier::new("foo")?), true.into()),
///     (ObjectKey::from("baz qux"), vec![1u64, 2].into()),
///     (ObjectKey::from("hello"), "world".into()),
/// ]));
///
/// assert_eq!(expression, expected);
/// #     Ok(())
/// # }
/// ```
#[macro_export]
macro_rules! expression {
    // Hide distracting implementation details from the generated rustdoc.
    ($($expr:tt)+) => {
        $crate::expression_internal!($($expr)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! expression_internal {
    //////////////////////////////////////////////////////////////////////////
    // TT muncher for parsing the inside of an array [...].
    //
    // Produces a vec![...] of the elements.
    //
    // Must be invoked as: expression_internal!(@array [] $($tt)*)
    //////////////////////////////////////////////////////////////////////////

    // Done with trailing comma.
    (@array [$($elems:expr,)*]) => {
        std::vec![$($elems,)*]
    };

    // Done without trailing comma.
    (@array [$($elems:expr),*]) => {
        std::vec![$($elems),*]
    };

    // Next element is `null`.
    (@array [$($elems:expr,)*] null $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!(null)] $($rest)*)
    };

    // Next element is `true`.
    (@array [$($elems:expr,)*] true $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!(true)] $($rest)*)
    };

    // Next element is `false`.
    (@array [$($elems:expr,)*] false $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!(false)] $($rest)*)
    };

    // Next element is an array.
    (@array [$($elems:expr,)*] [$($array:tt)*] $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!([$($array)*])] $($rest)*)
    };

    // Next element is a map.
    (@array [$($elems:expr,)*] {$($map:tt)*} $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!({$($map)*})] $($rest)*)
    };

    // Next element is an expression followed by comma.
    (@array [$($elems:expr,)*] $next:expr, $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!($next),] $($rest)*)
    };

    // Last element is an expression with no trailing comma.
    (@array [$($elems:expr,)*] $last:expr) => {
        $crate::expression_internal!(@array [$($elems,)* $crate::expression_internal!($last)])
    };

    // Comma after the most recent element.
    (@array [$($elems:expr),*] , $($rest:tt)*) => {
        $crate::expression_internal!(@array [$($elems,)*] $($rest)*)
    };

    // Unexpected token after most recent element.
    (@array [$($elems:expr),*] $unexpected:tt $($rest:tt)*) => {
        $crate::hcl_unexpected!($unexpected)
    };

    //////////////////////////////////////////////////////////////////////////
    // TT muncher for parsing the inside of an object {...}. Each entry is
    // inserted into the given map variable.
    //
    // Must be invoked as: expression_internal!(@object $map () ($($tt)*) ($($tt)*))
    //
    // We require two copies of the input tokens so that we can match on one
    // copy and trigger errors on the other copy.
    //////////////////////////////////////////////////////////////////////////

    // Done.
    (@object $object:ident () () ()) => {};

    // Insert the current entry followed by trailing comma.
    (@object $object:ident [$key:expr] ($value:expr) , $($rest:tt)*) => {
        let _ = $object.insert($key, $value);
        $crate::expression_internal!(@object $object () ($($rest)*) ($($rest)*));
    };

    // Insert the current entry not followed by trailing comma.
    (@object $object:ident [$key:expr] ($value:expr) $($rest:tt)*) => {
        let _ = $object.insert($key, $value);
        $crate::expression_internal!(@object $object () ($($rest)*) ($($rest)*));
    };

    // Insert the last entry without trailing comma.
    (@object $object:ident [$key:expr] ($value:expr)) => {
        let _ = $object.insert($key, $value);
    };

    // Next value is `null`.
    (@object $object:ident ($key:expr) (= null $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!(null)) $($rest)*);
    };

    // Next value is `true`.
    (@object $object:ident ($key:expr) (= true $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!(true)) $($rest)*);
    };

    // Next value is `false`.
    (@object $object:ident ($key:expr) (= false $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!(false)) $($rest)*);
    };

    // Next value is an array.
    (@object $object:ident ($key:expr) (= [$($array:tt)*] $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!([$($array)*])) $($rest)*);
    };

    // Next value is a map.
    (@object $object:ident ($key:expr) (= {$($map:tt)*} $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!({$($map)*})) $($rest)*);
    };

    // Next value is an expression followed by comma.
    (@object $object:ident ($key:expr) (= $value:expr , $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!($value)) , $($rest)*);
    };

    // Next value is an expression not followed by comma.
    (@object $object:ident ($key:expr) (= $value:tt $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!($value)) $($rest)*);
    };

    // Last value is an expression with no trailing comma.
    (@object $object:ident ($key:expr) (= $value:expr) $copy:tt) => {
        $crate::expression_internal!(@object $object [$key] ($crate::expression_internal!($value)));
    };

    // Missing value for last entry. Trigger a reasonable error message.
    (@object $object:ident ($key:expr) (=) $copy:tt) => {
        // "unexpected end of macro invocation"
        $crate::expression_internal!();
    };

    // Missing equals and value for last entry. Trigger a reasonable error
    // message.
    (@object $object:ident ($key:expr) () $copy:tt) => {
        // "unexpected end of macro invocation"
        $crate::expression_internal!();
    };

    // Misplaced equals. Trigger a reasonable error message.
    (@object $object:ident () (= $($rest:tt)*) ($equals:tt $($copy:tt)*)) => {
        // Takes no arguments so "no rules expected the token `:`".
        $crate::hcl_unexpected!($equals);
    };

    // Found a comma inside a key. Trigger a reasonable error message.
    (@object $object:ident ($key:expr) (, $($rest:tt)*) ($comma:tt $($copy:tt)*)) => {
        // Takes no arguments so "no rules expected the token `,`".
        $crate::hcl_unexpected!($comma);
    };

    // Refuse to absorb equals token into key expression.
    (@object $object:ident ($key:expr) (= $($unexpected:tt)+) $copy:tt) => {
        $crate::hcl_expect_expr_comma!($($unexpected)+);
    };

    // Munch an identifier key.
    (@object $object:ident () ($key:ident $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object ($crate::object_key!($key)) ($($rest)*) ($($rest)*));
    };

    // Munch a literal key.
    (@object $object:ident () ($key:literal $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object ($crate::object_key!($key)) ($($rest)*) ($($rest)*));
    };

    // Munch a parenthesized expression key.
    (@object $object:ident () (($key:expr) $($rest:tt)*) $copy:tt) => {
        $crate::expression_internal!(@object $object ($crate::object_key!(($key))) ($($rest)*) ($($rest)*));
    };

    //////////////////////////////////////////////////////////////////////////
    // The main implementation.
    //
    // Must be invoked as: expression_internal!($($expr)+)
    //////////////////////////////////////////////////////////////////////////

    (null) => {
        $crate::expr::Expression::Null
    };

    (true) => {
        $crate::expr::Expression::Bool(true)
    };

    (false) => {
        $crate::expr::Expression::Bool(false)
    };

    ([]) => {
        $crate::expr::Expression::Array(std::vec![])
    };

    ([ $($tt:tt)+ ]) => {
        $crate::expr::Expression::Array($crate::expression_internal!(@array [] $($tt)+))
    };

    ({}) => {
        $crate::expr::Expression::Object($crate::expr::Object::new())
    };

    ({ $($tt:tt)+ }) => {
        $crate::expr::Expression::Object({
            let mut object = $crate::expr::Object::new();
            $crate::expression_internal!(@object object () ($($tt)+) ($($tt)+));
            object
        })
    };

    // Any Serialize type: numbers, strings, struct literals, variables etc.
    // Must be below every other rule.
    ($other:expr) => {
        $crate::expr::to_expression(&$other).unwrap()
    };
}

/// Construct an `hcl::Value` from an HCL attribute value value literal.
///
/// Supports the same input syntax as the [`expression!`] macro, with the exception of raw value
/// expressions.
///
/// For supported syntax see the [`body!`] macro documentation.
///
/// # Example
///
/// ```
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// use hcl::{Value, Identifier, Map};
///
/// let other = "hello";
///
/// let value = hcl::value!({
///     foo       = true
///     "baz qux" = [1, 2]
///     (other)   = "world"
/// });
///
/// let expected = Value::Object({
///     let mut object = Map::new();
///     object.insert("foo".into(), true.into());
///     object.insert("baz qux".into(), vec![1u64, 2].into());
///     object.insert("hello".into(), "world".into());
///     object
/// });
///
/// assert_eq!(value, expected);
/// #     Ok(())
/// # }
/// ```
#[macro_export]
macro_rules! value {
    // Hide distracting implementation details from the generated rustdoc.
    ($($expr:tt)+) => {
        $crate::value_internal!($($expr)+)
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! value_internal {
    //////////////////////////////////////////////////////////////////////////
    // TT muncher for parsing the inside of an array [...].
    //
    // Produces a vec![...] of the elements.
    //
    // Must be invoked as: value_internal!(@array [] $($tt)*)
    //////////////////////////////////////////////////////////////////////////

    // Done with trailing comma.
    (@array [$($elems:expr,)*]) => {
        std::vec![$($elems,)*]
    };

    // Done without trailing comma.
    (@array [$($elems:expr),*]) => {
        std::vec![$($elems),*]
    };

    // Next element is `null`.
    (@array [$($elems:expr,)*] null $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!(null)] $($rest)*)
    };

    // Next element is `true`.
    (@array [$($elems:expr,)*] true $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!(true)] $($rest)*)
    };

    // Next element is `false`.
    (@array [$($elems:expr,)*] false $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!(false)] $($rest)*)
    };

    // Next element is an array.
    (@array [$($elems:expr,)*] [$($array:tt)*] $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!([$($array)*])] $($rest)*)
    };

    // Next element is a map.
    (@array [$($elems:expr,)*] {$($map:tt)*} $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!({$($map)*})] $($rest)*)
    };

    // Next element is an value followed by comma.
    (@array [$($elems:expr,)*] $next:expr, $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!($next),] $($rest)*)
    };

    // Last element is an value with no trailing comma.
    (@array [$($elems:expr,)*] $last:expr) => {
        $crate::value_internal!(@array [$($elems,)* $crate::value_internal!($last)])
    };

    // Comma after the most recent element.
    (@array [$($elems:expr),*] , $($rest:tt)*) => {
        $crate::value_internal!(@array [$($elems,)*] $($rest)*)
    };

    // Unexpected token after most recent element.
    (@array [$($elems:expr),*] $unexpected:tt $($rest:tt)*) => {
        $crate::hcl_unexpected!($unexpected)
    };

    //////////////////////////////////////////////////////////////////////////
    // TT muncher for parsing the inside of an object {...}. Each entry is
    // inserted into the given map variable.
    //
    // Must be invoked as: value_internal!(@object $map () ($($tt)*) ($($tt)*))
    //
    // We require two copies of the input tokens so that we can match on one
    // copy and trigger errors on the other copy.
    //////////////////////////////////////////////////////////////////////////

    // Done.
    (@object $object:ident () () ()) => {};

    // Insert the current entry followed by trailing comma.
    (@object $object:ident [$key:expr] ($value:expr) , $($rest:tt)*) => {
        let _ = $object.insert(($key).into(), $value);
        $crate::value_internal!(@object $object () ($($rest)*) ($($rest)*));
    };

    // Insert the current entry not followed by trailing comma.
    (@object $object:ident [$key:expr] ($value:expr) $($rest:tt)*) => {
        let _ = $object.insert(($key).into(), $value);
        $crate::value_internal!(@object $object () ($($rest)*) ($($rest)*));
    };

    // Insert the last entry without trailing comma.
    (@object $object:ident [$key:expr] ($value:expr)) => {
        let _ = $object.insert(($key).into(), $value);
    };

    // Next value is `null`.
    (@object $object:ident ($key:expr) (= null $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!(null)) $($rest)*);
    };

    // Next value is `true`.
    (@object $object:ident ($key:expr) (= true $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!(true)) $($rest)*);
    };

    // Next value is `false`.
    (@object $object:ident ($key:expr) (= false $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!(false)) $($rest)*);
    };

    // Next value is an array.
    (@object $object:ident ($key:expr) (= [$($array:tt)*] $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!([$($array)*])) $($rest)*);
    };

    // Next value is a map.
    (@object $object:ident ($key:expr) (= {$($map:tt)*} $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!({$($map)*})) $($rest)*);
    };

    // Next value is an value followed by comma.
    (@object $object:ident ($key:expr) (= $value:expr , $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!($value)) , $($rest)*);
    };

    // Next value is an value not followed by comma.
    (@object $object:ident ($key:expr) (= $value:tt $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!($value)) $($rest)*);
    };

    // Last value is an value with no trailing comma.
    (@object $object:ident ($key:expr) (= $value:expr) $copy:tt) => {
        $crate::value_internal!(@object $object [$key] ($crate::value_internal!($value)));
    };

    // Missing value for last entry. Trigger a reasonable error message.
    (@object $object:ident ($key:expr) (=) $copy:tt) => {
        // "unexpected end of macro invocation"
        $crate::value_internal!();
    };

    // Missing equals and value for last entry. Trigger a reasonable error
    // message.
    (@object $object:ident ($key:expr) () $copy:tt) => {
        // "unexpected end of macro invocation"
        $crate::value_internal!();
    };

    // Misplaced equals. Trigger a reasonable error message.
    (@object $object:ident () (= $($rest:tt)*) ($equals:tt $($copy:tt)*)) => {
        // Takes no arguments so "no rules expected the token `:`".
        $crate::hcl_unexpected!($equals);
    };

    // Found a comma inside a key. Trigger a reasonable error message.
    (@object $object:ident ($key:expr) (, $($rest:tt)*) ($comma:tt $($copy:tt)*)) => {
        // Takes no arguments so "no rules expected the token `,`".
        $crate::hcl_unexpected!($comma);
    };

    // Refuse to absorb equals token into key value.
    (@object $object:ident ($key:expr) (= $($unexpected:tt)+) $copy:tt) => {
        $crate::hcl_expect_expr_comma!($($unexpected)+);
    };

    // Munch an identifier key.
    (@object $object:ident () ($key:ident $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object ((std::stringify!($key))) ($($rest)*) ($($rest)*));
    };

    // Munch a literal key.
    (@object $object:ident () ($key:literal $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object (($key)) ($($rest)*) ($($rest)*));
    };

    // Munch a parenthesized value key.
    (@object $object:ident () (($key:expr) $($rest:tt)*) $copy:tt) => {
        $crate::value_internal!(@object $object (($key)) ($($rest)*) ($($rest)*));
    };

    //////////////////////////////////////////////////////////////////////////
    // The main implementation.
    //
    // Must be invoked as: value_internal!($($expr)+)
    //////////////////////////////////////////////////////////////////////////

    (null) => {
        $crate::value::Value::Null
    };

    (true) => {
        $crate::value::Value::Bool(true)
    };

    (false) => {
        $crate::value::Value::Bool(false)
    };

    ([]) => {
        $crate::value::Value::Array(std::vec![])
    };

    ([ $($tt:tt)+ ]) => {
        $crate::value::Value::Array($crate::value_internal!(@array [] $($tt)+))
    };

    ({}) => {
        $crate::value::Value::Object($crate::value::Map::new())
    };

    ({ $($tt:tt)+ }) => {
        $crate::value::Value::Object({
            let mut object = $crate::value::Map::new();
            $crate::value_internal!(@object object () ($($tt)+) ($($tt)+));
            object
        })
    };

    // Any Serialize type: numbers, strings, struct literals, variables etc.
    // Must be below every other rule.
    ($other:expr) => {
        $crate::value::to_value(&$other).unwrap()
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! hcl_unexpected {
    () => {};
}

#[macro_export]
#[doc(hidden)]
macro_rules! hcl_expect_expr_comma {
    ($e:expr , $($tt:tt)*) => {};
}

#[macro_export]
#[doc(hidden)]
macro_rules! serialize_unsupported {
    (bool) => {
        $crate::serialize_unsupported_method!{serialize_bool(v: bool)}
    };
    (i8) => {
        $crate::serialize_unsupported_method!{serialize_i8(v: i8)}
    };
    (i16) => {
        $crate::serialize_unsupported_method!{serialize_i16(v: i16)}
    };
    (i32) => {
        $crate::serialize_unsupported_method!{serialize_i32(v: i32)}
    };
    (i64) => {
        $crate::serialize_unsupported_method!{serialize_i64(v: i64)}
    };
    (i128) => {
        serde::serde_if_integer128! {
            $crate::serialize_unsupported_method!{serialize_i128(v: i128)}
        }
    };
    (u8) => {
        $crate::serialize_unsupported_method!{serialize_u8(v: u8)}
    };
    (u16) => {
        $crate::serialize_unsupported_method!{serialize_u16(v: u16)}
    };
    (u32) => {
        $crate::serialize_unsupported_method!{serialize_u32(v: u32)}
    };
    (u64) => {
        $crate::serialize_unsupported_method!{serialize_u64(v: u64)}
    };
    (u128) => {
        serde::serde_if_integer128! {
            $crate::serialize_unsupported_method!{serialize_u128(v: u128)}
        }
    };
    (f32) => {
        $crate::serialize_unsupported_method!{serialize_f32(v: f32)}
    };
    (f64) => {
        $crate::serialize_unsupported_method!{serialize_f64(v: f64)}
    };
    (char) => {
        $crate::serialize_unsupported_method!{serialize_char(v: char)}
    };
    (str) => {
        $crate::serialize_unsupported_method!{serialize_str(v: &str)}
    };
    (bytes) => {
        $crate::serialize_unsupported_method!{serialize_bytes(v: &[u8])}
    };
    (some) => {
        $crate::serialize_unsupported_method!{serialize_some<T>(value: &T)}
    };
    (none) => {
        $crate::serialize_unsupported_method!{serialize_none()}
    };
    (unit) => {
        $crate::serialize_unsupported_method!{serialize_unit()}
    };
    (unit_struct) => {
        $crate::serialize_unsupported_method!{serialize_unit_struct(name: &'static str)}
    };
    (unit_variant) => {
        $crate::serialize_unsupported_method!{serialize_unit_variant(name: &'static str, variant_index: u32, variant: &'static str)}
    };
    (newtype_struct) => {
        $crate::serialize_unsupported_method!{serialize_newtype_struct<T>(name: &'static str, value: &T)}
    };
    (newtype_variant) => {
        $crate::serialize_unsupported_method!{serialize_newtype_variant<T>(name: &'static str, variant_index: u32, variant: &'static str, value: &T)}
    };
    (seq) => {
        $crate::serialize_unsupported_method!{serialize_seq(len: Option<usize>) -> Result<SerializeSeq>}
    };
    (tuple) => {
        $crate::serialize_unsupported_method!{serialize_tuple(len: usize) -> Result<SerializeTuple>}
    };
    (tuple_struct) => {
        $crate::serialize_unsupported_method!{serialize_tuple_struct(name: &'static str, len: usize) -> Result<SerializeTupleStruct>}
    };
    (tuple_variant) => {
        $crate::serialize_unsupported_method!{serialize_tuple_variant(name: &'static str, variant_index: u32, variant: &'static str, len: usize) -> Result<SerializeTupleVariant>}
    };
    (map) => {
        $crate::serialize_unsupported_method!{serialize_map(len: Option<usize>) -> Result<SerializeMap>}
    };
    (struct) => {
        $crate::serialize_unsupported_method!{serialize_struct(name: &'static str, len: usize) -> Result<SerializeStruct>}
    };
    (struct_variant) => {
        $crate::serialize_unsupported_method!{serialize_struct_variant(name: &'static str, variant_index: u32, variant: &'static str, len: usize) -> Result<SerializeStructVariant>}
    };
    ($($func:ident)*) => {
        $($crate::serialize_unsupported!{$func})*
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! serialize_unsupported_method {
    ($func:ident<T>($($arg:ident : $ty:ty),*)) => {
        #[inline]
        fn $func<T>(self, $($arg: $ty,)*) -> $crate::Result<Self::Ok, Self::Error>
        where
            T: ?Sized + serde::ser::Serialize,
        {
            $(
                let _ = $arg;
            )*
            Err(serde::ser::Error::custom(std::format!("`{}` not supported", std::stringify!($func))))
        }
    };
    ($func:ident($($arg:ident : $ty:ty),*) -> Result<$rty:ident>) => {
        #[inline]
        fn $func(self, $($arg: $ty,)*) -> $crate::Result<Self::$rty, Self::Error> {
            $(
                let _ = $arg;
            )*
            Err(serde::ser::Error::custom(std::format!("`{}` not supported", std::stringify!($func))))
        }
    };
    ($func:ident($($arg:ident : $ty:ty),*)) => {
        #[inline]
        fn $func(self, $($arg: $ty,)*) -> $crate::Result<Self::Ok, Self::Error> {
            $(
                let _ = $arg;
            )*
            Err(serde::ser::Error::custom(std::format!("`{}` not supported", std::stringify!($func))))
        }
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! serialize_self {
    (some) => {
        $crate::serialize_self_method!{serialize_some()}
    };
    (newtype_struct) => {
        $crate::serialize_self_method!{serialize_newtype_struct(name: &'static str)}
    };
    (newtype_variant) => {
        $crate::serialize_self_method!{serialize_newtype_variant(name: &'static str, variant_index: u32, variant: &'static str)}
    };
    ($($func:ident)*) => {
        $($crate::serialize_self!{$func})*
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! serialize_self_method {
    ($func:ident($($arg:ident : $ty:ty),*)) => {
        #[inline]
        fn $func<T>(self, $($arg: $ty,)* value: &T) -> $crate::Result<Self::Ok, Self::Error>
        where
            T: ?Sized + serde::ser::Serialize,
        {
            $(
                let _ = $arg;
            )*
            value.serialize(self)
        }
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! forward_to_serialize_seq {
    (tuple) => {
        $crate::forward_to_serialize_seq_method!{serialize_tuple() -> Result<SerializeTuple>}
    };
    (tuple_struct) => {
        $crate::forward_to_serialize_seq_method!{serialize_tuple_struct(name: &'static str) -> Result<SerializeTupleStruct>}
    };
    ($($func:ident)*) => {
        $($crate::forward_to_serialize_seq!{$func})*
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! forward_to_serialize_seq_method {
    ($func:ident($($arg:ident : $ty:ty),*) -> Result<$rty:ident>) => {
        #[inline]
        fn $func(self, $($arg: $ty,)* len: usize) -> $crate::Result<Self::$rty, Self::Error> {
            $(
                let _ = $arg;
            )*
            self.serialize_seq(Some(len))
        }
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_forward_to_serialize_seq {
    ($method:ident, $ok:ty, $error:ty) => {
        type Ok = $ok;
        type Error = $error;
        impl_forward_to_serialize_seq!($method);
    };
    ($method:ident, $ok:ty) => {
        impl_forward_to_serialize_seq!($method, $ok, $crate::Error);
    };
    ($method:ident) => {
        fn $method<T>(&mut self, value: &T) -> $crate::Result<(), Self::Error>
        where
            T: ?Sized + serde::ser::Serialize,
        {
            serde::ser::SerializeSeq::serialize_element(self, value)
        }

        fn end(self) -> $crate::Result<Self::Ok, Self::Error> {
            serde::ser::SerializeSeq::end(self)
        }
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_forward_to_inner {
    ($ty:ty, $($tt:tt)+) => {
        type Ok = $ty;
        type Error = $crate::Error;

        impl_forward_to_inner_internal!($($tt)+);

        fn end(self) -> $crate::Result<Self::Ok, Self::Error> {
            self.inner.end().map(Into::into)
        }
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_forward_to_inner_internal {
    ($method:ident($($arg:ident: $ty:ty),*) $(,$rest:tt)*) => {
        fn $method<T>(&mut self, $($arg: $ty,)* value: &T) -> $crate::Result<(), Self::Error>
        where
            T: ?Sized + serde::ser::Serialize,
        {
            self.inner.$method($($arg,)* value)
        }

        impl_forward_to_inner_internal!($($rest),*);
    };
    ($method:ident $(,$rest:tt)*) => {
        impl_forward_to_inner_internal!($method() $(,$rest)*);
    };
    () => {};
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_deserialize_enum {
    () => {
        fn deserialize_enum<V>(
            self,
            _name: &'static str,
            _variants: &'static [&'static str],
            visitor: V,
        ) -> $crate::Result<V::Value, Self::Error>
        where
            V: serde::de::Visitor<'de>,
        {
            visitor.visit_enum($crate::de::EnumAccess::new(self))
        }
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_variant_name {
    ($($ty:ident => { $($variant:ident),+ }),*) => {
        $(
            impl $crate::de::VariantName for $ty {
                fn variant_name(&self) -> &'static str {
                    match self {
                        $(
                            $ty::$variant { .. } => std::stringify!($variant),
                        )*
                    }
                }
            }
        )*
    };
}

#[macro_export]
#[doc(hidden)]
macro_rules! impl_into_map_access_deserializer {
    ($($ty:ty => $access:ident),*) => {
        $(
            impl<'de> serde::de::IntoDeserializer<'de, Error> for $ty {
                type Deserializer = serde::de::value::MapAccessDeserializer<$access>;

                fn into_deserializer(self) -> Self::Deserializer {
                    serde::de::value::MapAccessDeserializer::new($access::new(self))
                }
            }
        )*
    };
}