add load_internal

compiler/load_internal/src/docs.rs

@@ -0,0 +1,445 @@
+use crate::docs::DocEntry::DetachedDoc;
+use crate::docs::TypeAnnotation::{
+    Apply, BoundVariable, Function, NoTypeAnn, ObscuredRecord, ObscuredTagUnion, Record, TagUnion,
+};
+use crate::file::LoadedModule;
+use roc_can::scope::Scope;
+use roc_error_macros::todo_abilities;
+use roc_module::ident::ModuleName;
+use roc_module::symbol::IdentIds;
+use roc_parse::ast::CommentOrNewline;
+use roc_parse::ast::{self, TypeHeader};
+use roc_parse::ast::{AssignedField, Def};
+use roc_region::all::Loc;
+
+// Documentation generation requirements
+
+#[derive(Debug)]
+pub struct Documentation {
+    pub name: String,
+    pub version: String,
+    pub docs: String,
+    pub modules: Vec<LoadedModule>,
+}
+
+#[derive(Debug)]
+pub struct ModuleDocumentation {
+    pub name: String,
+    pub entries: Vec<DocEntry>,
+    pub scope: Scope,
+}
+
+#[derive(Debug, Clone)]
+pub enum DocEntry {
+    DocDef(DocDef),
+    DetachedDoc(String),
+}
+
+#[derive(Debug, Clone)]
+pub struct DocDef {
+    pub name: String,
+    pub type_vars: Vec<String>,
+    pub type_annotation: TypeAnnotation,
+    pub docs: Option<String>,
+}
+
+#[derive(Debug, Clone)]
+pub enum TypeAnnotation {
+    TagUnion {
+        tags: Vec<Tag>,
+        extension: Box<TypeAnnotation>,
+    },
+    Function {
+        args: Vec<TypeAnnotation>,
+        output: Box<TypeAnnotation>,
+    },
+    ObscuredTagUnion,
+    ObscuredRecord,
+    BoundVariable(String),
+    Apply {
+        name: String,
+        parts: Vec<TypeAnnotation>,
+    },
+    Record {
+        fields: Vec<RecordField>,
+        extension: Box<TypeAnnotation>,
+    },
+    Wildcard,
+    NoTypeAnn,
+}
+#[derive(Debug, Clone)]
+pub enum RecordField {
+    RecordField {
+        name: String,
+        type_annotation: TypeAnnotation,
+    },
+    OptionalField {
+        name: String,
+        type_annotation: TypeAnnotation,
+    },
+    LabelOnly {
+        name: String,
+    },
+}
+
+#[derive(Debug, Clone)]
+pub struct Tag {
+    pub name: String,
+    pub values: Vec<TypeAnnotation>,
+}
+
+pub fn generate_module_docs<'a>(
+    scope: Scope,
+    module_name: ModuleName,
+    ident_ids: &'a IdentIds,
+    parsed_defs: &'a [Loc<ast::Def<'a>>],
+) -> ModuleDocumentation {
+    let (entries, _) =
+        parsed_defs
+            .iter()
+            .fold((vec![], None), |(acc, maybe_comments_after), def| {
+                generate_entry_doc(ident_ids, acc, maybe_comments_after, &def.value)
+            });
+
+    ModuleDocumentation {
+        name: module_name.as_str().to_string(),
+        scope,
+        entries,
+    }
+}
+
+fn detached_docs_from_comments_and_new_lines<'a>(
+    comments_or_new_lines: &'a [roc_parse::ast::CommentOrNewline<'a>],
+) -> Vec<String> {
+    let mut detached_docs: Vec<String> = Vec::new();
+
+    let mut docs = String::new();
+
+    for comment_or_new_line in comments_or_new_lines.iter() {
+        match comment_or_new_line {
+            CommentOrNewline::DocComment(doc_str) => {
+                docs.push_str(doc_str);
+                docs.push('\n');
+            }
+
+            CommentOrNewline::LineComment(_) | CommentOrNewline::Newline => {
+                if !docs.is_empty() {
+                    detached_docs.push(docs.clone());
+                }
+
+                docs = String::new();
+            }
+        }
+    }
+
+    detached_docs
+}
+
+fn generate_entry_doc<'a>(
+    ident_ids: &'a IdentIds,
+    mut acc: Vec<DocEntry>,
+    before_comments_or_new_lines: Option<&'a [roc_parse::ast::CommentOrNewline<'a>]>,
+    def: &'a ast::Def<'a>,
+) -> (
+    Vec<DocEntry>,
+    Option<&'a [roc_parse::ast::CommentOrNewline<'a>]>,
+) {
+    use roc_parse::ast::Pattern;
+
+    match def {
+        Def::SpaceBefore(sub_def, comments_or_new_lines) => {
+            // Comments before a definition are attached to the current definition
+
+            for detached_doc in detached_docs_from_comments_and_new_lines(comments_or_new_lines) {
+                acc.push(DetachedDoc(detached_doc));
+            }
+
+            generate_entry_doc(ident_ids, acc, Some(comments_or_new_lines), sub_def)
+        }
+
+        Def::SpaceAfter(sub_def, comments_or_new_lines) => {
+            let (new_acc, _) =
+                // If there are comments before, attach to this definition
+                generate_entry_doc(ident_ids, acc, before_comments_or_new_lines, sub_def);
+
+            // Comments after a definition are attached to the next definition
+            (new_acc, Some(comments_or_new_lines))
+        }
+
+        Def::Annotation(loc_pattern, loc_ann) => match loc_pattern.value {
+            Pattern::Identifier(identifier) => {
+                // Check if the definition is exposed
+                if ident_ids.get_id(&identifier.into()).is_some() {
+                    let name = identifier.to_string();
+                    let doc_def = DocDef {
+                        name,
+                        type_annotation: type_to_docs(false, loc_ann.value),
+                        type_vars: Vec::new(),
+                        docs: before_comments_or_new_lines.and_then(comments_or_new_lines_to_docs),
+                    };
+                    acc.push(DocEntry::DocDef(doc_def));
+                }
+                (acc, None)
+            }
+
+            _ => (acc, None),
+        },
+        Def::AnnotatedBody {
+            ann_pattern,
+            ann_type,
+            ..
+        } => match ann_pattern.value {
+            Pattern::Identifier(identifier) => {
+                // Check if the definition is exposed
+                if ident_ids.get_id(&identifier.into()).is_some() {
+                    let doc_def = DocDef {
+                        name: identifier.to_string(),
+                        type_annotation: type_to_docs(false, ann_type.value),
+                        type_vars: Vec::new(),
+                        docs: before_comments_or_new_lines.and_then(comments_or_new_lines_to_docs),
+                    };
+                    acc.push(DocEntry::DocDef(doc_def));
+                }
+                (acc, None)
+            }
+
+            _ => (acc, None),
+        },
+
+        Def::Alias {
+            header: TypeHeader { name, vars },
+            ann,
+        } => {
+            let mut type_vars = Vec::new();
+
+            for var in vars.iter() {
+                if let Pattern::Identifier(ident_name) = var.value {
+                    type_vars.push(ident_name.to_string());
+                }
+            }
+
+            let doc_def = DocDef {
+                name: name.value.to_string(),
+                type_annotation: type_to_docs(false, ann.value),
+                type_vars,
+                docs: before_comments_or_new_lines.and_then(comments_or_new_lines_to_docs),
+            };
+            acc.push(DocEntry::DocDef(doc_def));
+
+            (acc, None)
+        }
+
+        Def::Opaque {
+            header: TypeHeader { name, vars },
+            ..
+        } => {
+            let mut type_vars = Vec::new();
+
+            for var in vars.iter() {
+                if let Pattern::Identifier(ident_name) = var.value {
+                    type_vars.push(ident_name.to_string());
+                }
+            }
+
+            let doc_def = DocDef {
+                name: name.value.to_string(),
+                type_annotation: TypeAnnotation::NoTypeAnn,
+                type_vars,
+                docs: before_comments_or_new_lines.and_then(comments_or_new_lines_to_docs),
+            };
+            acc.push(DocEntry::DocDef(doc_def));
+
+            (acc, None)
+        }
+
+        Def::Ability { .. } => todo_abilities!(),
+
+        Def::Body(_, _) => (acc, None),
+
+        Def::Expect(c) => todo!("documentation for tests {:?}", c),
+
+        Def::NotYetImplemented(s) => todo!("{}", s),
+    }
+}
+
+fn type_to_docs(in_func_type_ann: bool, type_annotation: ast::TypeAnnotation) -> TypeAnnotation {
+    match type_annotation {
+        ast::TypeAnnotation::TagUnion { tags, ext } => {
+            let mut tags_to_render: Vec<Tag> = Vec::new();
+
+            let mut any_tags_are_private = false;
+
+            for tag in tags.iter() {
+                match tag_to_doc(in_func_type_ann, tag.value) {
+                    None => {
+                        any_tags_are_private = true;
+                        break;
+                    }
+                    Some(tag_ann) => {
+                        tags_to_render.push(tag_ann);
+                    }
+                }
+            }
+
+            if any_tags_are_private {
+                if in_func_type_ann {
+                    ObscuredTagUnion
+                } else {
+                    NoTypeAnn
+                }
+            } else {
+                let extension = match ext {
+                    None => NoTypeAnn,
+                    Some(ext_type_ann) => type_to_docs(in_func_type_ann, ext_type_ann.value),
+                };
+
+                TagUnion {
+                    tags: tags_to_render,
+                    extension: Box::new(extension),
+                }
+            }
+        }
+        ast::TypeAnnotation::BoundVariable(var_name) => BoundVariable(var_name.to_string()),
+        ast::TypeAnnotation::Apply(module_name, type_name, type_ann_parts) => {
+            let mut name = String::new();
+
+            if !module_name.is_empty() {
+                name.push_str(module_name);
+                name.push('.');
+            }
+
+            name.push_str(type_name);
+
+            let mut parts: Vec<TypeAnnotation> = Vec::new();
+
+            for type_ann_part in type_ann_parts {
+                parts.push(type_to_docs(in_func_type_ann, type_ann_part.value));
+            }
+
+            Apply { name, parts }
+        }
+        ast::TypeAnnotation::Record { fields, ext } => {
+            let mut doc_fields = Vec::new();
+
+            let mut any_fields_include_private_tags = false;
+
+            for field in fields.items {
+                match record_field_to_doc(in_func_type_ann, field.value) {
+                    None => {
+                        any_fields_include_private_tags = true;
+                        break;
+                    }
+                    Some(doc_field) => {
+                        doc_fields.push(doc_field);
+                    }
+                }
+            }
+            if any_fields_include_private_tags {
+                if in_func_type_ann {
+                    ObscuredRecord
+                } else {
+                    NoTypeAnn
+                }
+            } else {
+                let extension = match ext {
+                    None => NoTypeAnn,
+                    Some(ext_type_ann) => type_to_docs(in_func_type_ann, ext_type_ann.value),
+                };
+
+                Record {
+                    fields: doc_fields,
+                    extension: Box::new(extension),
+                }
+            }
+        }
+        ast::TypeAnnotation::SpaceBefore(&sub_type_ann, _) => {
+            type_to_docs(in_func_type_ann, sub_type_ann)
+        }
+        ast::TypeAnnotation::SpaceAfter(&sub_type_ann, _) => {
+            type_to_docs(in_func_type_ann, sub_type_ann)
+        }
+        ast::TypeAnnotation::Function(ast_arg_anns, output_ann) => {
+            let mut doc_arg_anns = Vec::new();
+
+            for ast_arg_ann in ast_arg_anns {
+                doc_arg_anns.push(type_to_docs(true, ast_arg_ann.value));
+            }
+
+            Function {
+                args: doc_arg_anns,
+                output: Box::new(type_to_docs(true, output_ann.value)),
+            }
+        }
+        ast::TypeAnnotation::Wildcard => TypeAnnotation::Wildcard,
+        _ => NoTypeAnn,
+    }
+}
+
+fn record_field_to_doc(
+    in_func_ann: bool,
+    field: ast::AssignedField<'_, ast::TypeAnnotation>,
+) -> Option<RecordField> {
+    match field {
+        AssignedField::RequiredValue(name, _, type_ann) => Some(RecordField::RecordField {
+            name: name.value.to_string(),
+            type_annotation: type_to_docs(in_func_ann, type_ann.value),
+        }),
+        AssignedField::SpaceBefore(&sub_field, _) => record_field_to_doc(in_func_ann, sub_field),
+        AssignedField::SpaceAfter(&sub_field, _) => record_field_to_doc(in_func_ann, sub_field),
+        AssignedField::OptionalValue(name, _, type_ann) => Some(RecordField::OptionalField {
+            name: name.value.to_string(),
+            type_annotation: type_to_docs(in_func_ann, type_ann.value),
+        }),
+        AssignedField::LabelOnly(label) => Some(RecordField::LabelOnly {
+            name: label.value.to_string(),
+        }),
+        AssignedField::Malformed(_) => None,
+    }
+}
+
+// The Option here represents if it is private. Private tags
+// evaluate to `None`.
+fn tag_to_doc(in_func_ann: bool, tag: ast::Tag) -> Option<Tag> {
+    match tag {
+        ast::Tag::Global { name, args } => Some(Tag {
+            name: name.value.to_string(),
+            values: {
+                let mut type_vars = Vec::new();
+
+                for arg in args {
+                    type_vars.push(type_to_docs(in_func_ann, arg.value));
+                }
+
+                type_vars
+            },
+        }),
+        ast::Tag::Private { .. } => None,
+        ast::Tag::SpaceBefore(&sub_tag, _) => tag_to_doc(in_func_ann, sub_tag),
+        ast::Tag::SpaceAfter(&sub_tag, _) => tag_to_doc(in_func_ann, sub_tag),
+        ast::Tag::Malformed(_) => None,
+    }
+}
+
+fn comments_or_new_lines_to_docs<'a>(
+    comments_or_new_lines: &'a [roc_parse::ast::CommentOrNewline<'a>],
+) -> Option<String> {
+    let mut docs = String::new();
+
+    for comment_or_new_line in comments_or_new_lines.iter() {
+        match comment_or_new_line {
+            CommentOrNewline::DocComment(doc_str) => {
+                docs.push_str(doc_str);
+                docs.push('\n');
+            }
+            CommentOrNewline::Newline | CommentOrNewline::LineComment(_) => {
+                docs = String::new();
+            }
+        }
+    }
+
+    if docs.is_empty() {
+        None
+    } else {
+        Some(docs)
+    }
+}

compiler/load_internal/src/lib.rs

@@ -0,0 +1,9 @@
+#![warn(clippy::dbg_macro)]
+// See github.com/rtfeldman/roc/issues/800 for discussion of the large_enum_variant check.
+#![allow(clippy::large_enum_variant)]
+pub mod docs;
+pub mod file;
+mod work;
+
+#[cfg(target_family = "wasm")]
+mod wasm_system_time;

compiler/load_internal/src/wasm_system_time.rs

@@ -0,0 +1,42 @@
+#![cfg(target_family = "wasm")]
+/*
+For the Web REPL (repl_www), we build the compiler as a Wasm module.
+SystemTime is the only thing in the compiler that would need a special implementation for this.
+There is a WASI implementation for it, but we are targeting the browser, not WASI!
+It's possible to write browser versions of WASI's low-level ABI but we'd rather avoid it.
+Instead we use these dummy implementations, which should just disappear at compile time.
+*/
+
+#[derive(Debug, Clone, Copy)]
+pub struct SystemTime;
+
+impl SystemTime {
+    pub fn now() -> Self {
+        SystemTime
+    }
+    pub fn duration_since(&self, _: SystemTime) -> Result<Duration, String> {
+        Ok(Duration)
+    }
+    pub fn elapsed(&self) -> Result<Duration, String> {
+        Ok(Duration)
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct Duration;
+
+impl Duration {
+    pub fn checked_sub(&self, _: Duration) -> Option<Duration> {
+        Some(Duration)
+    }
+}
+
+impl Default for Duration {
+    fn default() -> Self {
+        Duration
+    }
+}
+
+impl std::ops::AddAssign for Duration {
+    fn add_assign(&mut self, _: Duration) {}
+}

compiler/load_internal/src/work.rs

@@ -0,0 +1,290 @@
+use roc_collections::all::{MutMap, MutSet};
+use roc_module::symbol::{ModuleId, PackageQualified};
+
+use std::collections::hash_map::Entry;
+
+/// NOTE the order of definition of the phases is used by the ord instance
+/// make sure they are ordered from first to last!
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy, Debug)]
+pub enum Phase {
+    LoadHeader,
+    Parse,
+    CanonicalizeAndConstrain,
+    SolveTypes,
+    FindSpecializations,
+    MakeSpecializations,
+}
+
+/// NOTE keep up to date manually, from ParseAndGenerateConstraints to the highest phase we support
+const PHASES: [Phase; 6] = [
+    Phase::LoadHeader,
+    Phase::Parse,
+    Phase::CanonicalizeAndConstrain,
+    Phase::SolveTypes,
+    Phase::FindSpecializations,
+    Phase::MakeSpecializations,
+];
+
+#[derive(Debug)]
+enum Status {
+    NotStarted,
+    Pending,
+    Done,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+enum Job<'a> {
+    Step(ModuleId, Phase),
+    ResolveShorthand(&'a str),
+}
+
+#[derive(Default, Debug)]
+pub struct Dependencies<'a> {
+    waiting_for: MutMap<Job<'a>, MutSet<Job<'a>>>,
+    notifies: MutMap<Job<'a>, MutSet<Job<'a>>>,
+    status: MutMap<Job<'a>, Status>,
+}
+
+impl<'a> Dependencies<'a> {
+    /// Add all the dependencies for a module, return (module, phase) pairs that can make progress
+    pub fn add_module(
+        &mut self,
+        module_id: ModuleId,
+        dependencies: &MutSet<PackageQualified<'a, ModuleId>>,
+        goal_phase: Phase,
+    ) -> MutSet<(ModuleId, Phase)> {
+        use Phase::*;
+
+        let mut output = MutSet::default();
+
+        for dep in dependencies.iter() {
+            let has_package_dependency = self.add_package_dependency(dep, Phase::LoadHeader);
+
+            let dep = *dep.as_inner();
+
+            if !has_package_dependency {
+                // loading can start immediately on this dependency
+                output.insert((dep, Phase::LoadHeader));
+            }
+
+            // to parse and generate constraints, the headers of all dependencies must be loaded!
+            // otherwise, we don't know whether an imported symbol is actually exposed
+            self.add_dependency_help(module_id, dep, Phase::Parse, Phase::LoadHeader);
+
+            // to canonicalize a module, all its dependencies must be canonicalized
+            self.add_dependency(module_id, dep, Phase::CanonicalizeAndConstrain);
+
+            // to typecheck a module, all its dependencies must be type checked already
+            self.add_dependency(module_id, dep, Phase::SolveTypes);
+
+            if goal_phase >= FindSpecializations {
+                self.add_dependency(module_id, dep, Phase::FindSpecializations);
+            }
+
+            if goal_phase >= MakeSpecializations {
+                self.add_dependency(dep, module_id, Phase::MakeSpecializations);
+            }
+        }
+
+        // add dependencies for self
+        // phase i + 1 of a file always depends on phase i being completed
+        {
+            let mut i = 0;
+            while PHASES[i] < goal_phase {
+                self.add_dependency_help(module_id, module_id, PHASES[i + 1], PHASES[i]);
+                i += 1;
+            }
+        }
+
+        self.add_to_status(module_id, goal_phase);
+
+        output
+    }
+
+    fn add_to_status(&mut self, module_id: ModuleId, goal_phase: Phase) {
+        for phase in PHASES.iter() {
+            if *phase > goal_phase {
+                break;
+            }
+
+            if let Entry::Vacant(entry) = self.status.entry(Job::Step(module_id, *phase)) {
+                entry.insert(Status::NotStarted);
+            }
+        }
+    }
+
+    /// Propagate a notification, return (module, phase) pairs that can make progress
+    pub fn notify(&mut self, module_id: ModuleId, phase: Phase) -> MutSet<(ModuleId, Phase)> {
+        self.notify_help(Job::Step(module_id, phase))
+    }
+
+    /// Propagate a notification, return (module, phase) pairs that can make progress
+    pub fn notify_package(&mut self, shorthand: &'a str) -> MutSet<(ModuleId, Phase)> {
+        self.notify_help(Job::ResolveShorthand(shorthand))
+    }
+
+    fn notify_help(&mut self, key: Job<'a>) -> MutSet<(ModuleId, Phase)> {
+        self.status.insert(key.clone(), Status::Done);
+
+        let mut output = MutSet::default();
+
+        if let Some(to_notify) = self.notifies.get(&key) {
+            for notify_key in to_notify {
+                let mut is_empty = false;
+                if let Some(waiting_for_pairs) = self.waiting_for.get_mut(notify_key) {
+                    waiting_for_pairs.remove(&key);
+                    is_empty = waiting_for_pairs.is_empty();
+                }
+
+                if is_empty {
+                    self.waiting_for.remove(notify_key);
+
+                    if let Job::Step(module, phase) = *notify_key {
+                        output.insert((module, phase));
+                    }
+                }
+            }
+        }
+
+        self.notifies.remove(&key);
+
+        output
+    }
+
+    fn add_package_dependency(
+        &mut self,
+        module: &PackageQualified<'a, ModuleId>,
+        next_phase: Phase,
+    ) -> bool {
+        match module {
+            PackageQualified::Unqualified(_) => {
+                // no dependency, we can just start loading the file
+                false
+            }
+            PackageQualified::Qualified(shorthand, module_id) => {
+                let job = Job::ResolveShorthand(shorthand);
+                let next_step = Job::Step(*module_id, next_phase);
+                match self.status.get(&job) {
+                    None | Some(Status::NotStarted) | Some(Status::Pending) => {
+                        // this shorthand is not resolved, add a dependency
+                        {
+                            let entry = self
+                                .waiting_for
+                                .entry(next_step.clone())
+                                .or_insert_with(Default::default);
+
+                            entry.insert(job.clone());
+                        }
+
+                        {
+                            let entry = self.notifies.entry(job).or_insert_with(Default::default);
+
+                            entry.insert(next_step);
+                        }
+
+                        true
+                    }
+                    Some(Status::Done) => {
+                        // shorthand is resolved; no dependency
+                        false
+                    }
+                }
+            }
+        }
+    }
+
+    /// A waits for B, and B will notify A when it completes the phase
+    fn add_dependency(&mut self, a: ModuleId, b: ModuleId, phase: Phase) {
+        self.add_dependency_help(a, b, phase, phase);
+    }
+
+    /// phase_a of module a is waiting for phase_b of module_b
+    fn add_dependency_help(&mut self, a: ModuleId, b: ModuleId, phase_a: Phase, phase_b: Phase) {
+        // no need to wait if the dependency is already done!
+        if let Some(Status::Done) = self.status.get(&Job::Step(b, phase_b)) {
+            return;
+        }
+
+        let key = Job::Step(a, phase_a);
+        let value = Job::Step(b, phase_b);
+        match self.waiting_for.get_mut(&key) {
+            Some(existing) => {
+                existing.insert(value);
+            }
+            None => {
+                let mut set = MutSet::default();
+                set.insert(value);
+                self.waiting_for.insert(key, set);
+            }
+        }
+
+        let key = Job::Step(b, phase_b);
+        let value = Job::Step(a, phase_a);
+        match self.notifies.get_mut(&key) {
+            Some(existing) => {
+                existing.insert(value);
+            }
+            None => {
+                let mut set = MutSet::default();
+                set.insert(value);
+                self.notifies.insert(key, set);
+            }
+        }
+    }
+
+    pub fn solved_all(&self) -> bool {
+        debug_assert_eq!(self.notifies.is_empty(), self.waiting_for.is_empty());
+
+        for status in self.status.values() {
+            match status {
+                Status::Done => {
+                    continue;
+                }
+                _ => {
+                    return false;
+                }
+            }
+        }
+
+        true
+    }
+
+    pub fn prepare_start_phase(&mut self, module_id: ModuleId, phase: Phase) -> PrepareStartPhase {
+        match self.status.get_mut(&Job::Step(module_id, phase)) {
+            Some(current @ Status::NotStarted) => {
+                // start this phase!
+                *current = Status::Pending;
+                PrepareStartPhase::Continue
+            }
+            Some(Status::Pending) => {
+                // don't start this task again!
+                PrepareStartPhase::Done
+            }
+            Some(Status::Done) => {
+                // don't start this task again, but tell those waiting for it they can continue
+                let new = self.notify(module_id, phase);
+
+                PrepareStartPhase::Recurse(new)
+            }
+            None => match phase {
+                Phase::LoadHeader => {
+                    // this is fine, mark header loading as pending
+                    self.status
+                        .insert(Job::Step(module_id, Phase::LoadHeader), Status::Pending);
+
+                    PrepareStartPhase::Continue
+                }
+                _ => unreachable!(
+                    "Pair {:?} is not in dependencies.status, that should never happen!",
+                    (module_id, phase)
+                ),
+            },
+        }
+    }
+}
+
+pub enum PrepareStartPhase {
+    Continue,
+    Done,
+    Recurse(MutSet<(ModuleId, Phase)>),
+}