Implements make_struct (#876)

src/lazy/expanded/e_expression.rs

@@ -11,7 +11,8 @@ use crate::lazy::expanded::compiler::{ExpansionAnalysis, ExpansionSingleton};
 use crate::lazy::expanded::macro_evaluator::{
     AnnotateExpansion, ConditionalExpansion, EExpressionArgGroup, ExprGroupExpansion,
     FlattenExpansion, IsExhaustedIterator, MacroExpansion, MacroExpansionKind, MacroExpr,
-    MacroExprArgsIterator, MakeTextExpansion, RawEExpression, TemplateExpansion, ValueExpr,
+    MacroExprArgsIterator, MakeStructExpansion, MakeTextExpansion, RawEExpression,
+    TemplateExpansion, ValueExpr,
 };
 use crate::lazy::expanded::macro_table::{MacroKind, MacroRef};
 use crate::lazy::expanded::template::TemplateMacroRef;
@@ -123,6 +124,9 @@ impl<'top, D: Decoder> EExpression<'top, D> {
             MacroKind::MakeSymbol => {
                 MacroExpansionKind::MakeSymbol(MakeTextExpansion::symbol_maker(arguments))
             }
+            MacroKind::MakeStruct => {
+                MacroExpansionKind::MakeStruct(MakeStructExpansion::new(arguments))
+            }
             MacroKind::Annotate => MacroExpansionKind::Annotate(AnnotateExpansion::new(arguments)),
             MacroKind::Flatten => MacroExpansionKind::Flatten(FlattenExpansion::new(
                 self.context,

src/lazy/expanded/macro_evaluator.rs

@@ -35,8 +35,8 @@ use crate::lazy::text::raw::v1_1::arg_group::EExpArg;
 use crate::lazy::text::raw::v1_1::reader::MacroIdRef;
 use crate::result::IonFailure;
 use crate::{
-    ExpandedValueRef, ExpandedValueSource, IonError, IonResult, LazyValue, Span, SymbolRef,
-    ValueRef,
+    ExpandedValueRef, ExpandedValueSource, IonError, IonResult, LazyExpandedStruct, LazyStruct,
+    LazyValue, Span, SymbolRef, ValueRef,
 };
 
 pub trait IsExhaustedIterator<'top, D: Decoder>:
@@ -459,6 +459,7 @@ pub enum MacroExpansionKind<'top, D: Decoder> {
     ExprGroup(ExprGroupExpansion<'top, D>),
     MakeString(MakeTextExpansion<'top, D>),
     MakeSymbol(MakeTextExpansion<'top, D>),
+    MakeStruct(MakeStructExpansion<'top, D>),
     Annotate(AnnotateExpansion<'top, D>),
     Flatten(FlattenExpansion<'top, D>),
     Template(TemplateExpansion<'top>),
@@ -540,6 +541,7 @@ impl<'top, D: Decoder> MacroExpansion<'top, D> {
             ExprGroup(expr_group_expansion) => expr_group_expansion.next(context, environment),
             MakeString(make_string_expansion) => make_string_expansion.make_text_value(context),
             MakeSymbol(make_symbol_expansion) => make_symbol_expansion.make_text_value(context),
+            MakeStruct(make_struct_expansion) => make_struct_expansion.next(context, environment),
             Annotate(annotate_expansion) => annotate_expansion.next(context, environment),
             Flatten(flatten_expansion) => flatten_expansion.next(),
             Conditional(cardiality_test_expansion) => cardiality_test_expansion.next(environment),
@@ -556,6 +558,7 @@ impl<D: Decoder> Debug for MacroExpansion<'_, D> {
             MacroExpansionKind::ExprGroup(_) => "[internal] expr_group",
             MacroExpansionKind::MakeString(_) => "make_string",
             MacroExpansionKind::MakeSymbol(_) => "make_symbol",
+            MacroExpansionKind::MakeStruct(_) => "make_struct",
             MacroExpansionKind::Annotate(_) => "annotate",
             MacroExpansionKind::Flatten(_) => "flatten",
             MacroExpansionKind::Conditional(test) => test.name(),
@@ -1112,6 +1115,40 @@ impl<'top, D: Decoder> ConditionalExpansion<'top, D> {
     }
 }
 
+// ===== Implementation of the `make_struct` macro =====
+#[derive(Copy, Clone, Debug)]
+pub struct MakeStructExpansion<'top, D: Decoder> {
+    arguments: MacroExprArgsIterator<'top, D>,
+}
+
+impl<'top, D: Decoder> MakeStructExpansion<'top, D> {
+    pub fn new(arguments: MacroExprArgsIterator<'top, D>) -> Self {
+        Self { arguments }
+    }
+
+    fn next(
+        &mut self,
+        context: EncodingContextRef<'top>,
+        environment: Environment<'top, D>,
+    ) -> IonResult<MacroExpansionStep<'top, D>> {
+        // The `make_struct` macro always produces a single struct value. When `next()` is called
+        // to begin its evaluation, it immediately returns a lazy value representing the (not yet
+        // computed) struct. If/when the application tries to iterate over its fields,
+        // the iterator will evaluate the field expressions incrementally.
+        let lazy_expanded_struct =
+            LazyExpandedStruct::from_constructed(context, environment, self.arguments);
+        let lazy_struct = LazyStruct::new(lazy_expanded_struct);
+        // Store the `Struct` in the bump so it's guaranteed to be around as long as the reader is
+        // positioned on this top-level value.
+        let value_ref = context
+            .allocator()
+            .alloc_with(|| ValueRef::Struct(lazy_struct));
+        let lazy_expanded_value = LazyExpandedValue::from_constructed(context, &[], value_ref);
+        Ok(MacroExpansionStep::FinalStep(Some(
+            ValueExpr::ValueLiteral(lazy_expanded_value),
+        )))
+    }
+}
 // ===== Implementation of the `make_string` macro =====
 
 #[derive(Copy, Clone, Debug)]
@@ -2788,6 +2825,28 @@ mod tests {
         )
     }
 
+    #[test]
+    fn make_struct_eexp() -> IonResult<()> {
+        stream_eq(
+            r#"
+            (:make_struct)
+            (:make_struct {a: 1})
+            (:make_struct {a: 1} {})
+            (:make_struct {a: 1} {b: 2})
+            (:make_struct {a: 1} {b: 2} {a: 3, d: 4})
+            (:make_struct {a: 1} {b: 2} {a: 3, d: 4} (:make_struct {e: 5} {f: 6}))
+        "#,
+            r#"
+            {}
+            {a: 1}
+            {a: 1}
+            {a: 1, b: 2}
+            {a: 1, b: 2, a: 3, d: 4}
+            {a: 1, b: 2, a: 3, d: 4, e: 5, f: 6}
+        "#,
+        )
+    }
+
     #[test]
     fn make_string_tdl_macro_invocation() -> IonResult<()> {
         let invocation = r#"

src/lazy/expanded/macro_table.rs

@@ -114,6 +114,7 @@ pub enum MacroKind {
     ExprGroup,
     MakeString,
     MakeSymbol,
+    MakeStruct,
     Annotate,
     Flatten,
     Template(TemplateBody),
@@ -317,7 +318,7 @@ impl MacroTable {
             builtin(
                 "make_struct",
                 "(fields*)",
-                MacroKind::ToDo,
+                MacroKind::MakeStruct,
                 ExpansionAnalysis::single_application_value(IonType::Struct),
             ),
             template(

src/lazy/expanded/mod.rs

@@ -1060,6 +1060,12 @@ pub enum ExpandedAnnotationsSource<'top, Encoding: Decoder> {
     Constructed(std::slice::Iter<'top, SymbolRef<'top>>),
 }
 
+impl<Encoding: Decoder> ExpandedAnnotationsSource<'_, Encoding> {
+    pub fn empty() -> Self {
+        Self::Constructed(std::slice::Iter::default())
+    }
+}
+
 pub struct ExpandedAnnotationsIterator<'top, Encoding: Decoder> {
     source: ExpandedAnnotationsSource<'top, Encoding>,
 }

src/lazy/expanded/struct.rs

@@ -2,7 +2,7 @@ use crate::element::iterators::SymbolsIterator;
 use crate::lazy::decoder::private::{LazyRawStructPrivate, RawStructUnexpandedFieldsIterator};
 use crate::lazy::decoder::{Decoder, LazyRawFieldName, LazyRawStruct};
 use crate::lazy::expanded::macro_evaluator::{
-    MacroEvaluator, MacroExpansion, MacroExpr, ValueExpr,
+    MacroEvaluator, MacroExpansion, MacroExpr, MacroExprArgsIterator, ValueExpr,
 };
 use crate::lazy::expanded::sequence::Environment;
 use crate::lazy::expanded::template::{
@@ -13,7 +13,7 @@ use crate::lazy::expanded::{
     LazyExpandedValue,
 };
 use crate::result::IonFailure;
-use crate::{try_or_some_err, IonResult, RawSymbolRef, SymbolRef};
+use crate::{try_next, try_or_some_err, IonResult, RawSymbolRef, SymbolRef};
 
 /// A unified type embodying all possible field representations coming from both input data
 /// (i.e. raw structs of some encoding) and template bodies.
@@ -48,6 +48,10 @@ impl<'top, D: Decoder> LazyExpandedField<'top, D> {
     pub fn name(&self) -> LazyExpandedFieldName<'top, D> {
         self.name
     }
+
+    pub fn unexpanded(&self) -> UnexpandedField<'top, D> {
+        UnexpandedField::NameValue(self.name(), self.value())
+    }
 }
 
 impl<'top, D: Decoder> LazyExpandedField<'top, D> {
@@ -107,14 +111,16 @@ pub enum ExpandedStructSource<'top, D: Decoder> {
         TemplateElement<'top>,
         &'top TemplateStructIndex,
     ),
-    // TODO: Constructed
+    // The struct was produced by the `make_struct` macro.
+    Constructed(Environment<'top, D>, MacroExprArgsIterator<'top, D>),
 }
 
 impl<'top, D: Decoder> ExpandedStructSource<'top, D> {
     fn environment(&self) -> Environment<'top, D> {
         match self {
             ExpandedStructSource::ValueLiteral(_) => Environment::empty(),
             ExpandedStructSource::Template(environment, _, _) => *environment,
+            ExpandedStructSource::Constructed(environment, _) => *environment,
         }
     }
 }
@@ -154,18 +160,27 @@ impl<'top, D: Decoder> LazyExpandedStruct<'top, D> {
         Self { source, context }
     }
 
+    pub fn from_constructed(
+        context: EncodingContextRef<'top>,
+        environment: Environment<'top, D>,
+        arguments: MacroExprArgsIterator<'top, D>,
+    ) -> LazyExpandedStruct<'top, D> {
+        let source = ExpandedStructSource::Constructed(environment, arguments);
+        Self { source, context }
+    }
+
     pub fn annotations(&self) -> ExpandedAnnotationsIterator<'top, D> {
-        match &self.source {
-            ExpandedStructSource::ValueLiteral(value) => ExpandedAnnotationsIterator {
-                source: ExpandedAnnotationsSource::ValueLiteral(value.annotations()),
-            },
+        let iter_source = match &self.source {
+            ExpandedStructSource::ValueLiteral(value) => {
+                ExpandedAnnotationsSource::ValueLiteral(value.annotations())
+            }
             ExpandedStructSource::Template(_environment, element, _index) => {
                 let annotations = element.annotations();
-                ExpandedAnnotationsIterator {
-                    source: ExpandedAnnotationsSource::Template(SymbolsIterator::new(annotations)),
-                }
+                ExpandedAnnotationsSource::Template(SymbolsIterator::new(annotations))
             }
-        }
+            ExpandedStructSource::Constructed(_, _) => ExpandedAnnotationsSource::empty(),
+        };
+        ExpandedAnnotationsIterator::new(iter_source)
     }
 
     pub fn iter(&self) -> ExpandedStructIterator<'top, D> {
@@ -197,6 +212,18 @@ impl<'top, D: Decoder> LazyExpandedStruct<'top, D> {
                     ),
                 )
             }
+            ExpandedStructSource::Constructed(environment, arguments) => {
+                let evaluator = self
+                    .context
+                    .allocator()
+                    .alloc_with(|| MacroEvaluator::new_with_environment(*environment));
+                let current_struct_iter = self.context.allocator().alloc_with(|| None);
+                ExpandedStructIteratorSource::Constructed(
+                    evaluator,
+                    current_struct_iter,
+                    *arguments,
+                )
+            }
         };
         ExpandedStructIterator {
             source,
@@ -214,9 +241,9 @@ impl<'top, D: Decoder> LazyExpandedStruct<'top, D> {
 
     pub fn find(&self, name: &str) -> IonResult<Option<LazyExpandedValue<'top, D>>> {
         match &self.source {
-            // If we're reading from a struct literal, do a linear scan over its fields until we
-            // encounter one with the requested name.
-            ExpandedStructSource::ValueLiteral(_) => {
+            // If we're reading from a struct literal or `make_struct` call, do a linear scan over
+            // its fields until we encounter one with the requested name.
+            ExpandedStructSource::ValueLiteral(_) | ExpandedStructSource::Constructed(_, _) => {
                 for field_result in self.iter() {
                     let field = field_result?;
                     if field.name().read()?.text() == Some(name) {
@@ -287,7 +314,14 @@ pub enum ExpandedStructIteratorSource<'top, D: Decoder> {
         &'top mut MacroEvaluator<'top, D>,
         TemplateStructUnexpandedFieldsIterator<'top, D>,
     ),
-    // TODO: Constructed
+    Constructed(
+        &'top mut MacroEvaluator<'top, D>,
+        // This is `&mut Option<_>` instead of `Option<&mut _>` so we can re-use the allocated space
+        // for each iterator we traverse.
+        &'top mut Option<ExpandedStructIterator<'top, D>>,
+        // Remaining argument expressions
+        MacroExprArgsIterator<'top, D>,
+    ),
 }
 
 impl<'top, D: Decoder> ExpandedStructIteratorSource<'top, D> {
@@ -300,13 +334,68 @@ impl<'top, D: Decoder> ExpandedStructIteratorSource<'top, D> {
             ExpandedStructIteratorSource::ValueLiteral(_, raw_struct_iter) => {
                 raw_struct_iter.next()
             }
+            ExpandedStructIteratorSource::Constructed(
+                evaluator,
+                maybe_current_struct,
+                arguments,
+            ) => {
+                loop {
+                    // If we're already traversing a struct, see if it has any fields remaining.
+                    if let Some(current_struct) = maybe_current_struct {
+                        match current_struct.next() {
+                            // If we get a field, we're done.
+                            Some(Ok(field)) => return Some(Ok(field.unexpanded())),
+                            Some(Err(e)) => return Some(Err(e)),
+                            // If we get `None`, the iterator is exhausted and we should continue on to the next struct.
+                            None => **maybe_current_struct = None,
+                        }
+                    }
+
+                    // If we reach this point, we don't have a current struct.
+                    // We've either just started evaluation and haven't set one yet or
+                    // we just finished inlining a struct and need to set a new one.
+
+                    // See if the evaluator has an expansion in progress.
+                    let mut next_struct = try_or_some_err!(evaluator.next());
+                    if next_struct.is_none() {
+                        // If we don't get anything from the evaluator, we'll get our struct from the
+                        // next argument expression. If there isn't a next argument expression,
+                        // then evaluation is complete.
+                        next_struct = match try_next!(arguments.next()) {
+                            // If the expression is a value literal, that's our new sequence.
+                            ValueExpr::ValueLiteral(value) => Some(value),
+                            // If the expression is a macro invocation, we'll start evaluating it
+                            // and return to the top of the loop.
+                            ValueExpr::MacroInvocation(invocation) => {
+                                evaluator.push(try_or_some_err!(invocation.expand()));
+                                continue;
+                            }
+                        }
+                    }
+
+                    // At this point, `next_struct` is definitely populated, so we can safely unwrap it.
+                    let next_struct = next_struct.unwrap();
+                    // Set it as our new current struct.
+                    let ExpandedValueRef::Struct(next_struct) =
+                        try_or_some_err!(next_struct.read())
+                    else {
+                        return Some(IonResult::decoding_error(format!(
+                            "`make_struct` only accepts structs, received {next_struct:?}"
+                        )));
+                    };
+                    **maybe_current_struct = Some(next_struct.iter());
+                }
+            }
         }
     }
 
     fn evaluator(&mut self) -> &mut MacroEvaluator<'top, D> {
+        // TODO: Should the evaluator be lifted out of the iterator source?
+        //       It is common to all of the variants.
         match self {
             ExpandedStructIteratorSource::Template(evaluator, _) => evaluator,
             ExpandedStructIteratorSource::ValueLiteral(evaluator, _) => evaluator,
+            ExpandedStructIteratorSource::Constructed(evaluator, _, _) => evaluator,
         }
     }
 }

src/lazy/expanded/template.rs

@@ -8,7 +8,7 @@ use compact_str::CompactString;
 use crate::lazy::binary::raw::v1_1::immutable_buffer::ArgGroupingBitmap;
 use crate::lazy::decoder::Decoder;
 use crate::lazy::expanded::compiler::ExpansionAnalysis;
-use crate::lazy::expanded::macro_evaluator::{AnnotateExpansion, MacroEvaluator, MacroExpansion, MacroExpansionKind, MacroExpr, MacroExprArgsIterator, TemplateExpansion, ValueExpr, ExprGroupExpansion, MakeTextExpansion, FlattenExpansion, ConditionalExpansion};
+use crate::lazy::expanded::macro_evaluator::{AnnotateExpansion, MacroEvaluator, MacroExpansion, MacroExpansionKind, MacroExpr, MacroExprArgsIterator, TemplateExpansion, ValueExpr, ExprGroupExpansion, MakeTextExpansion, FlattenExpansion, ConditionalExpansion, MakeStructExpansion};
 use crate::lazy::expanded::macro_table::{Macro, MacroKind};
 use crate::lazy::expanded::r#struct::UnexpandedField;
 use crate::lazy::expanded::sequence::Environment;
@@ -1221,6 +1221,9 @@ impl<'top, D: Decoder> TemplateMacroInvocation<'top, D> {
             MacroKind::MakeSymbol => {
                 MacroExpansionKind::MakeSymbol(MakeTextExpansion::symbol_maker(arguments))
             }
+            MacroKind::MakeStruct => {
+                MacroExpansionKind::MakeStruct(MakeStructExpansion::new(arguments))
+            }
             MacroKind::Annotate => MacroExpansionKind::Annotate(AnnotateExpansion::new(arguments)),
             MacroKind::Flatten => MacroExpansionKind::Flatten(FlattenExpansion::new(self.context(), self.environment, arguments)),
             MacroKind::Template(template_body) => {

src/lazy/struct.rs

@@ -93,12 +93,18 @@ impl<'top, D: Decoder> LazyStruct<'top, D> {
     }
 
     pub fn as_value(&self) -> LazyValue<'top, D> {
+        let context = self.expanded_struct.context;
         let expanded_value = match self.expanded_struct.source {
             ExpandedStructSource::ValueLiteral(v) => {
-                LazyExpandedValue::from_literal(self.expanded_struct.context, v.as_value())
+                LazyExpandedValue::from_literal(context, v.as_value())
             }
             ExpandedStructSource::Template(env, element, _) => {
-                LazyExpandedValue::from_template(self.expanded_struct.context, env, element)
+                LazyExpandedValue::from_template(context, env, element)
+            }
+            ExpandedStructSource::Constructed(_env, _args) => {
+                let value_ref = context.allocator().alloc_with(|| ValueRef::Struct(*self));
+                let annotations = &[];
+                LazyExpandedValue::from_constructed(context, annotations, value_ref)
             }
         };
         LazyValue::new(expanded_value)