Preparation for more parser work (#1363)

Cargo.toml

@@ -6,6 +6,7 @@ members = [
     "lib/rust/lexer/definition",
     "lib/rust/lexer/generation",
     "lib/rust/parser",
+    "lib/rust/parser-jni",
 ]
 
 # These patch versions exist to allow local development of these libraries alongside Enso. It

docs/parser/lexer.md

@@ -113,7 +113,7 @@ change made to the lexer. The lexer benchmarks are written using
 [criterion.rs](https://github.com/bheisler/criterion.rs), and include both
 examples of whole program definitions and more specific benchmark examples.
 
-**Baseline Commit:** TBC (use head of this branch for now).
+**Baseline Commit:** `e5695e6f5d44cba4094380545036a3a5cbbf6973`
 
 The benchmarking process for the lexer is as follows:
 

docs/parser/macro-resolution.md

@@ -40,6 +40,9 @@ used in the Enso parser itself.
 - [Macro Resolution Errors](#macro-resolution-errors)
   - [Macro Errors as Parser Errors](#macro-errors-as-parser-errors)
 - [User-Defined Macros](#user-defined-macros)
+- [Benchmarking](#benchmarking)
+  - [Running a Subset of the Benchmarks](#running-a-subset-of-the-benchmarks)
+  - [Changing the Macro Resolver](#changing-the-macro-resolver)
 
 <!-- /MarkdownTOC -->
 
@@ -255,3 +258,55 @@ define syntactic macros for their programs, similar to how Rust exposes the
 > - Determine what this should look like in surface Enso.
 > - Determine exactly how the round-trip mechanic between the runtime and parser
 >   should function.
+
+## Benchmarking
+
+All components of the macro resolver are accompanied by comprehensive benchmarks
+in order to protect the performance-crucial code against regressions. These
+benchmarks are written using
+[criterion.rs](https://github.com/bheisler/criterion.rs), and cover all of the
+performance critical functionality of the macro resolver.
+
+**Baseline Commit:** TBC (use the latest for now)
+
+The benchmarking process for the macro resolver is as follows:
+
+1. Check out the current _baseline commit_, listed above.
+2. In each of the benchmark files, change the configuration line reading
+   `.retain_baseline` to `.save_baseline`. This will save the current baseline
+   (taken on your machine).
+3. In `lexer_bench_sources.rs` change the line that reads `.retain_baseline` to
+   instead read `.save_baseline`. This will save the current baseline (taken on
+   your machine).
+4. Run the benchmarks using `cargo bench`.
+5. Once the baseline run has completed, change the above-mentioned lines back to
+   `.retain_baseline`. This will disable overwriting the saved baseline, and
+   will perform its regression reporting against it.
+6. Make your changes.
+7. Run the benchmark suite again. It will report any performance regressions in
+   the benchmark report, measured against your saved baseline.
+
+Unfortunately, the use of time-based benchmarks means that we can't commit the
+baseline to the repository. There is far too much variance between machines for
+this to be useful.
+
+### Running a Subset of the Benchmarks
+
+The benchmarks are very comprehensive, testing all performance-critical paths of
+the macro resolver. However, it can often be useful to run a subset of these.
+
+There are two main tuning points for this:
+
+1. The _sizes_ of inputs being executed on, where relevant.
+2. The benchmarks being executed.
+
+While it is _possible_ to tune the benchmarking config to decrease benchmarking
+time, this is not recommended. The current settings are tuned to provide
+reliable results.
+
+### Changing the Macro Resolver
+
+When changing the macro resolver the _full_ benchmark suite must be run against
+the current baseline before the changes can be merged. This suite run must use
+the provided settings for the benchmarking library, and should be performed
+using the process described above.

lib/rust/lexer/definition/src/token.rs

@@ -15,7 +15,7 @@ use crate::lexeme;
 // =============
 
 /// A lexer token.
-#[derive(Clone,Debug,Eq,PartialEq)]
+#[derive(Clone,Debug,Eq,Hash,PartialEq)]
 pub struct Token {
     /// The shape of the token.
     pub shape : Shape,
@@ -294,7 +294,7 @@ impl Token {
 // =================
 
 /// The type for an Enso Block token.
-#[derive(Copy,Clone,Debug,PartialEq,Eq)]
+#[derive(Copy,Clone,Debug,Eq,Hash,PartialEq)]
 pub enum BlockType {
     /// A block made up of arguments to a function.
     Continuous,
@@ -309,7 +309,7 @@ pub enum BlockType {
 // ==================
 
 /// The type of newline associated with the line.
-#[derive(Copy,Clone,Debug,Display,PartialEq,Eq)]
+#[derive(Copy,Clone,Debug,Display,Eq,Hash,PartialEq)]
 pub enum LineEnding {
     /// There is no newline.
     None,
@@ -348,7 +348,7 @@ impl Default for LineEnding {
 // =================
 
 /// The style of the text literal.
-#[derive(Copy,Clone,Debug,Eq,PartialEq)]
+#[derive(Copy,Clone,Debug,Eq,Hash,PartialEq)]
 pub enum TextStyle {
     // === Line ===
 
@@ -424,7 +424,7 @@ impl TextStyle {
 // ===================
 
 /// A description of the style of escape sequence seen.
-#[derive(Clone,Copy,Debug,Eq,PartialEq)]
+#[derive(Clone,Copy,Debug,Eq,Hash,PartialEq)]
 pub enum EscapeStyle {
     /// A \xNN-style byte escape.
     Byte,
@@ -474,7 +474,7 @@ impl EscapeStyle {
 /// This is a very small set of shapes, because the [`Token`] type only deals with the tokens that
 /// the lexer works with, not the full complexity of Enso's syntax.
 #[allow(missing_docs)]
-#[derive(Clone,Debug,PartialEq,Eq)]
+#[derive(Clone,Debug,Eq,Hash,PartialEq)]
 pub enum Shape {
     // === Identifiers ===
 
@@ -761,6 +761,11 @@ impl Stream {
     pub fn tokens_len(&self) -> usize {
         self.tokens.iter().map(|token|token.length + token.offset).sum()
     }
+
+    /// Get a consuming iterator over the token stream.
+    pub fn into_iter(self) -> std::vec::IntoIter<Token> {
+        self.tokens.into_iter()
+    }
 }
 
 impl Deref for Stream {

lib/rust/lexer/generation/benches/lexer_bench_sources.rs

@@ -2,9 +2,7 @@
 //! benchmarking the Enso lexer.
 
 use criterion::{black_box, Criterion, Throughput};
-use enso_flexer::prelude::Reader;
-use enso_flexer::prelude::reader::decoder::DecoderUTF8;
-use lexer::generated::engine::EnsoLexer;
+use lexer;
 use std::time::Duration;
 
 
@@ -51,9 +49,7 @@ pub fn run_bench_sizes(name:&str, input:&str, add_newline:bool, c:&mut Criterion
         group.bench_function(
             *size_name,
             |b| b.iter(|| {
-                let mut lexer = EnsoLexer::new();
-                let reader    = Reader::new(input.as_str().as_bytes(),DecoderUTF8());
-                lexer.run(black_box(reader));
+                lexer::run(black_box(input.as_str()));
             })
         );
     })

lib/rust/lexer/generation/src/lexer.rs

@@ -0,0 +1,21 @@
+//! A driver for the Enso lexer.
+
+use crate::prelude::*;
+
+use enso_flexer::LexingResult;
+use crate::library::token;
+use crate::generated::engine::EnsoLexer;
+use crate::prelude::reader::decoder::DecoderUTF8;
+
+
+
+// ====================
+// === Lexer Driver ===
+// ====================
+
+/// Execute the lexer on the provided `input`, assuming utf-8 encoding.
+pub fn run(input:impl AsRef<str>) -> LexingResult<token::Stream> {
+    let mut lexer = EnsoLexer::new();
+    let reader    = Reader::new(input.as_ref().as_bytes(),DecoderUTF8());
+    lexer.run(reader)
+}

lib/rust/lexer/generation/src/lib.rs

@@ -10,12 +10,15 @@
 
 //! This module exports the interface to the generated Enso lexer.
 
+pub mod lexer;
 pub mod generated;
 
+pub use crate::lexer::*;
+
 /// Support libraries for the lexer definition.
 ///
 /// This is an intentional re-export in this crate's namespace.
-mod library {
+pub mod library {
     pub use lexer_definition::library::*;
 }
 

lib/rust/lexer/generation/tests/test_utils.rs

@@ -5,9 +5,7 @@
 use enso_flexer::*;
 use lexer_definition::library::*;
 
-use enso_flexer::prelude::reader::decoder::DecoderUTF8;
-use enso_flexer::prelude::Reader;
-use lexer::generated::engine::EnsoLexer;
+use lexer;
 use lexer_definition::library::token::Token;
 
 
@@ -36,9 +34,7 @@ pub fn assert_lexes(input:impl AsRef<str>, expected:token::Stream) {
 
 /// Lex the provided string.
 pub fn lex(input:impl AsRef<str>) -> LexingResult<token::Stream> {
-    let mut lexer = EnsoLexer::new();
-    let reader    = Reader::new(input.as_ref().as_bytes(),DecoderUTF8());
-    lexer.run(reader)
+    lexer::run(input)
 }
 
 /// Asserts that the input is a block and has a length equal to `length`.

lib/rust/parser-jni/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name    = "parser-jni"
+version = "0.1.0"
+authors = ["Enso Team <enso-dev@enso.org>"]
+edition = "2018"
+
+description  = "A parser for the Enso language"
+readme       = "README.md"
+homepage     = "https://github.com/enso-org/enso/lib/rust/parser"
+repository   = "https://github.com/enso-org/enso"
+license-file = "../../../LICENSE"
+
+keywords   = ["parser"]
+categories = ["parsing"]
+
+publish = false
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+test       = true
+bench      = true
+
+[dependencies]
+jni = { version = "0.17.0"                  }
+ast = { version = "0.1.0",  path = "../ast" }

lib/rust/parser-jni/src/lib.rs

@@ -0,0 +1,47 @@
+#![feature(test)]
+#![deny(unconditional_recursion)]
+#![warn(missing_copy_implementations)]
+#![warn(missing_debug_implementations)]
+#![warn(missing_docs)]
+#![warn(trivial_casts)]
+#![warn(trivial_numeric_casts)]
+#![warn(unsafe_code)]
+#![warn(unused_import_braces)]
+
+//! This module exports the implementation of parser for the Enso language.
+
+mod jni;
+
+pub use crate::jni::*;
+
+use ast::AnyAst;
+use ast::Ast;
+
+
+
+// =======================
+// === Parser Rust API ===
+// =======================
+
+/// Parse a content of a single source file.
+pub fn parse_str(input:String) -> AnyAst {
+    Ast::new(ast::txt::Text{text:input})
+}
+
+/// Parse a single source file.
+pub fn parse_file(filename:String) -> AnyAst {
+    parse_str(filename)
+}
+
+
+// === Tokens ===
+
+/// Parse a content of single source file.
+pub fn lexe_str(input:String) -> AnyAst {
+    parse_str(input)
+}
+
+/// Parse a single source file.
+pub fn lexe_file(filename:String) -> AnyAst {
+    parse_str(filename)
+}

lib/rust/parser/Cargo.toml

@@ -4,23 +4,21 @@ version = "0.1.0"
 authors = ["Enso Team <enso-dev@enso.org>"]
 edition = "2018"
 
-description  = "A parser for the Enso language"
-readme       = "README.md"
-homepage     = "https://github.com/enso-org/enso/lib/rust/parser"
-repository   = "https://github.com/enso-org/enso"
-license-file = "../../../LICENSE"
-
-keywords   = ["parser"]
-categories = ["parsing"]
-
 publish = false
 
 [lib]
-name       = "parser"
 crate-type = ["cdylib", "rlib"]
 test       = true
 bench      = true
 
 [dependencies]
-jni = { version = "0.17.0"                  }
-ast = { version = "0.1.0",  path = "../ast" }
+enso-data    = { version = "0.1.3"                               }
+enso-logger  = { version = "0.1.3"                               }
+enso-prelude = { version = "0.1.8"                               }
+lexer        = { version = "0.1.0", path = "../lexer/generation" }
+itertools    = { version = "0.9.0"                               }
+
+[build-dependencies]
+
+[dev-dependencies]
+criterion = "0.3"

lib/rust/parser/src/lib.rs

@@ -1,47 +1,30 @@
-#![feature(test)]
-#![deny(unconditional_recursion)]
-#![warn(missing_copy_implementations)]
-#![warn(missing_debug_implementations)]
-#![warn(missing_docs)]
-#![warn(trivial_casts)]
-#![warn(trivial_numeric_casts)]
-#![warn(unsafe_code)]
-#![warn(unused_import_braces)]
+//! This library contains the implementation of the Enso parser.
 
-//! This module exports the implementation of parser for the Enso language.
+pub mod macros;
+pub mod operator;
+pub mod parser;
 
-mod jni;
+pub use crate::parser::*;
 
-pub use crate::jni::*;
+/// The prelude for the parser.
+pub mod prelude {
+    pub use enso_prelude::*;
+    pub use enso_logger::AnyLogger;
 
-use ast::AnyAst;
-use ast::Ast;
+    /// The Enso logging library.
+    pub mod logger {
+        pub use enso_logger::*;
+        pub use enso_logger::disabled::Logger as Disabled;
+        pub use enso_logger::enabled::Logger as Enabled;
+    }
 
+    /// The lexer types.
+    pub mod lexer {
+        pub use ::lexer::*;
 
-
-// =======================
-// === Parser Rust API ===
-// =======================
-
-/// Parse a content of a single source file.
-pub fn parse_str(input:String) -> AnyAst {
-    Ast::new(ast::txt::Text{text:input})
-}
-
-/// Parse a single source file.
-pub fn parse_file(filename:String) -> AnyAst {
-    parse_str(filename)
-}
-
-
-// === Tokens ===
-
-/// Parse a content of single source file.
-pub fn lexe_str(input:String) -> AnyAst {
-    parse_str(input)
-}
-
-/// Parse a single source file.
-pub fn lexe_file(filename:String) -> AnyAst {
-    parse_str(filename)
+        /// The lexer tokens.
+        pub mod token {
+            pub use lexer::library::token::*;
+        }
+    }
 }

lib/rust/parser/src/macros.rs

@@ -0,0 +1,41 @@
+//! The macro system for the Enso parser.
+
+pub mod definition;
+pub mod literal;
+pub mod registry;
+
+use crate::prelude::*;
+use crate::prelude::logger::*;
+
+use crate::macros::definition::Definition;
+use crate::macros::registry::Registry;
+
+
+
+// ================
+// === Resolver ===
+// ================
+
+/// The Enso macro resolver.
+#[derive(Clone,Debug,PartialEq)]
+#[allow(missing_docs)]
+pub struct Resolver<Logger> {
+    registry : Registry,
+    logger   : Logger
+}
+
+impl<Logger> Resolver<Logger>
+where Logger : AnyLogger<Owned=Logger> {
+    /// Constructor.
+    pub fn new(macros:Vec<Definition>, parent_logger:&Logger) -> Self {
+        let logger   = <Logger>::sub(parent_logger,"Resolver");
+        let registry = Registry::from(macros);
+        Self{registry,logger}
+    }
+
+    /// Define the macro described by `definition` in the macro resolver `self`.
+    pub fn define_macro(&mut self, definition:Definition) {
+        debug!(self.logger,"Define Macro: {&definition:?}.");
+        self.registry.insert(definition)
+    }
+}

lib/rust/parser/src/macros/definition.rs

@@ -0,0 +1,69 @@
+//! Macro definitions in Enso.
+
+use crate::prelude::*;
+use crate::macros::literal::Literal;
+use itertools::Itertools;
+
+
+
+// ==================
+// === Definition ===
+// ==================
+
+/// A macro definition.
+///
+/// A macro definition consists of a name, which identifies the macro to users, and a list of
+/// [sections](`Section`). The sections are the most important portion of the macro definition, as
+/// they define the literal portions of the token stream on which the macro will match.
+#[derive(Clone,Debug,Default,Eq,PartialEq)]
+#[allow(missing_docs)]
+pub struct Definition {
+    pub name     : String,
+    pub sections : Vec<Section>
+}
+
+impl Definition {
+    /// Constructor.
+    pub fn new(name:impl Str, sections:Vec<Section>) -> Self {
+        let name = name.into();
+        Self{name,sections}
+    }
+
+    /// Get the path for the definition.
+    ///
+    /// The definition's path consists of the headers of each of the sections that make it up, and
+    /// describes the literals that must be matched for the macro to match.
+    pub fn path(&self) -> Vec<Literal> {
+        self.sections.iter().map(|s| s.start_symbol.clone()).collect_vec()
+    }
+}
+
+
+
+// ===============
+// === Section ===
+// ===============
+
+/// A section in a macro, representing both a literal section header to match against, and the
+/// tokens that the section contains.
+///
+/// The literal is the _most_ important portion of a section, as they are constants that allow the
+/// macro resolver to divide up the input token stream based on these constants.
+#[derive(Clone,Debug,Eq,PartialEq)]
+#[allow(missing_docs)]
+pub struct Section {
+    start_symbol : Literal
+    // TODO Pattern
+}
+
+impl Section {
+    /// Constructor.
+    pub fn new(symbol:Literal) -> Self {
+        Self{ start_symbol: symbol }
+    }
+
+    /// Get a reference to the literal that heads the section.
+    pub fn start_symbol(&self) -> &Literal {
+        &self.start_symbol
+    }
+}

lib/rust/parser/src/macros/literal.rs

@@ -0,0 +1,95 @@
+//! This file contains the literal matchers that are used to head up macro sections.
+
+use crate::prelude::*;
+
+use crate::prelude::lexer::token;
+
+
+// ===============
+// === Literal ===
+// ===============
+
+/// The kinds of literal that can be the head of a macro section.
+///
+/// For more detailed descriptions of the various literal types, please see the documentation of the
+/// tokens in the Lexer.
+#[derive(Clone,Debug,Eq,Hash,Ord,PartialEq,PartialOrd)]
+pub enum Literal {
+    Referent(String),
+    Variable(String),
+    External(String),
+    Blank,
+    Operator(String),
+    Annotation(String)
+}
+
+impl Literal {
+
+    /// Construct a referent identifier literal.
+    pub fn referent(lit:impl Str) -> Literal {
+        Literal::Referent(lit.into())
+    }
+
+    /// Construct a variable identifier literal.
+    pub fn variable(lit:impl Str) -> Literal {
+        Literal::Variable(lit.into())
+    }
+
+    /// Construct an external identifier literal.
+    pub fn external(lit:impl Str) -> Literal {
+        Literal::External(lit.into())
+    }
+
+    /// Construct a blank identifier literal.
+    pub fn blank() -> Literal {
+        Literal::Blank
+    }
+
+    /// Construct an operator identifier literal.
+    pub fn operator(lit:impl Str) -> Literal {
+        Literal::Operator(lit.into())
+    }
+
+    /// Construct an annodation identifier literal.
+    pub fn annotation(lit:impl Str) -> Literal {
+        Literal::Annotation(lit.into())
+    }
+}
+
+
+// === Trait Impls ===
+
+impl From<&Literal> for Literal {
+    fn from(lit:&Literal) -> Self {
+        lit.clone()
+    }
+}
+
+impl From<Literal> for token::Shape {
+    fn from(lit:Literal) -> Self {
+        match lit {
+            Literal::Referent(str)   => token::Shape::Referent(str),
+            Literal::Variable(str)   => token::Shape::Variable(str),
+            Literal::External(str)   => token::Shape::External(str),
+            Literal::Blank           => token::Shape::Blank,
+            Literal::Operator(str)   => token::Shape::Operator(str),
+            Literal::Annotation(str) => token::Shape::Annotation(str),
+        }
+    }
+}
+
+impl TryFrom<token::Shape> for Literal {
+    type Error = token::Shape;
+
+    fn try_from(shape:token::Shape) -> Result<Self, Self::Error> {
+        match shape {
+            token::Shape::Referent(name)   => Ok(Literal::Referent(name)),
+            token::Shape::Variable(name)   => Ok(Literal::Variable(name)),
+            token::Shape::External(name)   => Ok(Literal::External(name)),
+            token::Shape::Blank            => Ok(Literal::Blank),
+            token::Shape::Operator(name)   => Ok(Literal::Operator(name)),
+            token::Shape::Annotation(name) => Ok(Literal::Annotation(name)),
+            _                              => Err(shape)
+        }
+    }
+}

lib/rust/parser/src/macros/registry.rs

@@ -0,0 +1,145 @@
+//! The macro registry that can be queried during the process of macro resolution.
+
+use crate::prelude::*;
+use enso_data::hash_map_tree::*;
+
+use crate::macros::definition::Definition;
+use crate::macros::literal::Literal;
+
+
+
+// ================
+// === Registry ===
+// ================
+
+/// The type of the tree that underlies the registry.
+pub type Tree = HashMapTree<Literal,Option<Definition>>;
+
+/// The registry is responsible for the registration of macro definitions, and the querying of said
+/// definitions.
+#[derive(Clone,Debug,Default,PartialEq)]
+#[allow(missing_docs)]
+pub struct Registry {
+    tree : Tree
+}
+
+impl Registry {
+    /// Insert `definition` into the macro registry.
+    pub fn insert(&mut self, definition:Definition) {
+        self.tree.set(definition.path(),Some(definition));
+    }
+
+    /// Get a reference to the root of the registry.
+    pub fn root(&self) -> &Tree {
+        &self.tree
+    }
+
+    /// Query the registry for a tree.
+    pub fn subtree<P>(&self, path:P) -> Option<&Tree>
+    where P:IntoIterator, P::Item:Into<Literal> {
+        self.tree.get_node(path)
+    }
+
+    /// Query the registry for a tree, assuming such a tree is present.
+    ///
+    /// # Panics
+    /// If no tree exists at `path`.
+    pub fn unsafe_subtree<P>(&self, path:P) -> &Tree
+    where P:IntoIterator, P::Item:Into<Literal> {
+        self.subtree(path).expect("A tree exists at the input path.")
+    }
+
+    /// Query the registry for a definition.
+    pub fn definition<P>(&self, path:P) -> Option<&Definition>
+    where P:IntoIterator, P::Item:Into<Literal> {
+        match self.tree.get(path) {
+            Some(Some(def)) => Some(def),
+            _ => None
+        }
+    }
+
+    /// Query the registry for a definition, assuming such a definition is present.
+    ///
+    /// # Panics
+    /// If no definition exists at `path`.
+    pub fn unsafe_definition<P>(&self, path:P) -> &Definition
+    where P:IntoIterator, P::Item:Into<Literal> {
+        self.definition(path).expect("A definition exists at the input path.")
+    }
+}
+
+
+// === Trait Impls ===
+
+impl From<Vec<Definition>> for Registry {
+    fn from(defs:Vec<Definition>) -> Self {
+        let mut registry:Registry = default();
+        defs.into_iter().for_each(|def| registry.insert(def));
+        registry
+    }
+}
+
+
+
+// =============
+// === Tests ===
+// =============
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::macros::definition::Section;
+
+    #[test]
+    fn insert_query() {
+        let mut registry = Registry::default();
+        let definition   = Definition::new("Test",vec![
+            Section::new(Literal::variable("if")),
+            Section::new(Literal::variable("then")),
+            Section::new(Literal::variable("else")),
+        ]);
+        let path_1 = &[Literal::variable("if"),Literal::variable("then"),Literal::variable("else")];
+        let path_2 = &[Literal::variable("if"),Literal::variable("then")];
+        registry.insert(definition.clone());
+        let result_1 = registry.definition(path_1);
+        let result_2 = registry.definition(path_2);
+        assert!(result_1.is_some());
+        assert_eq!(result_1.unwrap(),&definition);
+        assert_eq!(result_2,None);
+    }
+
+    #[test]
+    fn from_defs() {
+        let definitions = vec![
+            Definition::new("if_then_else", vec![
+                Section::new(Literal::variable("if")),
+                Section::new(Literal::variable("then")),
+                Section::new(Literal::variable("else")),
+            ]),
+            Definition::new("if_then", vec![
+                Section::new(Literal::variable("if")),
+                Section::new(Literal::variable("then")),
+            ]),
+            Definition::new("if_let", vec![
+                Section::new(Literal::variable("if")),
+                Section::new(Literal::variable("let")),
+            ]),
+        ];
+        let registry = Registry::from(definitions.clone());
+        let path_1   = &[Literal::variable("if"),Literal::variable("then"),Literal::variable("else")];
+        let path_2   = &[Literal::variable("if"),Literal::variable("then")];
+        let path_3   = &[Literal::variable("if"),Literal::variable("let")];
+        let path_4   = &[Literal::variable("if")];
+        let result_1 = registry.definition(path_1);
+        let result_2 = registry.definition(path_2);
+        let result_3 = registry.definition(path_3);
+        let result_4 = registry.definition(path_4);
+        assert!(result_1.is_some());
+        assert!(result_2.is_some());
+        assert!(result_3.is_some());
+        assert!(result_4.is_none());
+        assert_eq!(result_1,definitions.get(0));
+        assert_eq!(result_2,definitions.get(1));
+        assert_eq!(result_3,definitions.get(2));
+    }
+}

lib/rust/parser/src/operator.rs

@@ -0,0 +1,4 @@
+//! The logic for working with operators in the Enso parser.
+
+pub mod associativity;
+pub mod precedence;

lib/rust/parser/src/operator/associativity.rs

@@ -0,0 +1 @@
+//! Associativity inference for Enso.

lib/rust/parser/src/operator/precedence.rs

@@ -0,0 +1 @@
+//! Operator precedence levels.

lib/rust/parser/src/parser.rs

@@ -0,0 +1,18 @@
+//! The driver for the Enso parser.
+
+
+
+// ==============
+// === Parser ===
+// ==============
+
+/// The Enso parser itself.
+#[derive(Clone,Debug,Default,Eq,PartialEq)]
+pub struct Parser;
+
+impl Parser {
+    /// Constructor.
+    pub fn new() -> Self {
+        Self
+    }
+}