Cargo.toml

@@ -32,6 +32,7 @@ thiserror = "1.0.57"
 anyhow = "1.0.80"
 tracing = "0.1.40"
 tracing-subscriber = { version = "0.3.18", features = ["time", "json", "env-filter"] }
+names = "0.14.0"
 
 [build-dependencies]
 lalrpop = "0.20.2"

src/bin/gen_program.rs

@@ -0,0 +1,23 @@
+use ngr::syntax::ProgramGenerator;
+use ngr::util::pretty::Allocator;
+use proptest::strategy::{Strategy, ValueTree};
+use proptest::test_runner::{Config, TestRunner};
+
+fn main() -> Result<(), anyhow::Error> {
+    let generator = ProgramGenerator::default();
+    let runner_config = Config::default();
+    let mut runner = TestRunner::new(runner_config);
+    let program_tree = generator
+        .new_tree(&mut runner)
+        .map_err(|e| anyhow::anyhow!("Couldn't generate test program: {}", e))?;
+    let program = program_tree.current();
+    let allocator = Allocator::new();
+    let mut stdout = std::io::stdout();
+
+    for top_level in program.into_iter() {
+        let docbuilder = top_level.pretty(&allocator);
+        docbuilder.render(78, &mut stdout)?;
+    }
+
+    Ok(())
+}

src/syntax.rs

@@ -43,6 +43,7 @@ lalrpop_mod!(
 pub mod pretty;
 mod validate;
 
+pub use crate::syntax::arbitrary::ProgramGenerator;
 pub use crate::syntax::ast::*;
 pub use crate::syntax::location::Location;
 pub use crate::syntax::name::Name;

src/syntax/ast.rs

@@ -76,7 +76,7 @@ impl StructureDefinition {
 #[derive(Clone, Debug, PartialEq)]
 pub enum TopLevel {
     Expression(Expression),
-    Structure(Location, Name, Vec<(Name, Type)>),
+    Structure(Location, Name, Vec<(Name, Option<Type>)>),
 }
 
 impl Located for TopLevel {
@@ -205,6 +205,8 @@ pub enum Value {
     /// operation "-" on the number 4. We'll translate this into a type-specific
     /// number at a later time.
     Number(Option<u8>, Option<ConstantType>, u64),
+    /// The empty value
+    Void,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]

src/syntax/eval.rs

@@ -45,6 +45,8 @@ impl Expression {
                     Some(ConstantType::U32) => Ok(Value::U32(*v as u32)),
                     Some(ConstantType::U64) => Ok(Value::U64(*v)),
                 },
+
+                super::Value::Void => Ok(Value::Void),
             },
 
             Expression::Constructor(_, on, fields) => {

src/syntax/parser.lalrpop

@@ -92,9 +92,12 @@ Structure: TopLevel = {
     }
 }
 
-Field: (Name, Type) = {
+Field: (Name, Option<Type>) = {
     <s:@L> <name:"<var>"> <e:@L> ":" <field_type: Type> ";" =>
-        (Name::new(name, Location::new(file_idx, s..e)), field_type)
+        (Name::new(name, Location::new(file_idx, s..e)), Some(field_type)),
+    <s:@L> <name:"<var>"> <e:@L> ";" =>
+        (Name::new(name, Location::new(file_idx, s..e)), None),
+
 }
 
 Type: Type = {

src/syntax/pretty.rs

@@ -84,7 +84,10 @@ impl Program {
 impl TopLevel {
     pub fn pretty<'a>(&self, allocator: &'a Allocator<'a>) -> DocBuilder<'a, Allocator<'a>> {
         match self {
-            TopLevel::Expression(expr) => expr.pretty(allocator),
+            TopLevel::Expression(expr) => expr
+                .pretty(allocator)
+                .append(allocator.text(";"))
+                .append(allocator.hardline()),
             TopLevel::Structure(_, name, fields) => allocator
                 .text("struct")
                 .append(allocator.space())
@@ -95,17 +98,24 @@ impl TopLevel {
                 .append(
                     allocator
                         .concat(fields.iter().map(|(name, ty)| {
+                            let type_bit = if let Some(ty) = ty {
+                                allocator
+                                    .text(":")
+                                    .append(allocator.space())
+                                    .append(ty.pretty(allocator))
+                            } else {
+                                allocator.nil()
+                            };
                             allocator
                                 .text(name.to_string())
-                                .append(allocator.text(":"))
-                                .append(allocator.space())
-                                .append(ty.pretty(allocator))
+                                .append(type_bit)
                                 .append(allocator.text(";"))
                                 .append(allocator.hardline())
                         }))
                         .nest(2),
                 )
-                .append(allocator.text("}")),
+                .append(allocator.text("}"))
+                .append(allocator.hardline()),
         }
     }
 }
@@ -231,6 +241,8 @@ impl Value {
 
                 allocator.text(value_str)
             }
+
+            Value::Void => allocator.text("<void>"),
         }
     }
 }

src/syntax/tokens.rs

@@ -1,6 +1,6 @@
 use internment::ArcIntern;
 use logos::{Lexer, Logos};
-use std::fmt;
+use std::{fmt, str::FromStr};
 use thiserror::Error;
 
 /// A single token of the input stream; used to help the parsing go down
@@ -205,6 +205,43 @@ impl From<ConstantType> for cranelift_codegen::ir::Type {
     }
 }
 
+pub struct StringNotConstantType();
+
+impl FromStr for ConstantType {
+    type Err = StringNotConstantType;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "i8" => Ok(ConstantType::I8),
+            "i16" => Ok(ConstantType::I16),
+            "i32" => Ok(ConstantType::I32),
+            "i64" => Ok(ConstantType::I64),
+            "u8" => Ok(ConstantType::U8),
+            "u16" => Ok(ConstantType::U16),
+            "u32" => Ok(ConstantType::U32),
+            "u64" => Ok(ConstantType::U64),
+            "void" => Ok(ConstantType::Void),
+            _ => Err(StringNotConstantType()),
+        }
+    }
+}
+
+impl fmt::Display for ConstantType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ConstantType::I8 => write!(f, "i8"),
+            ConstantType::I16 => write!(f, "i16"),
+            ConstantType::I32 => write!(f, "i32"),
+            ConstantType::I64 => write!(f, "i64"),
+            ConstantType::U8 => write!(f, "u8"),
+            ConstantType::U16 => write!(f, "u16"),
+            ConstantType::U32 => write!(f, "u32"),
+            ConstantType::U64 => write!(f, "u64"),
+            ConstantType::Void => write!(f, "void"),
+        }
+    }
+}
+
 impl ConstantType {
     /// Return the set of types that can be safely casted into this type.
     pub fn safe_casts_to(self) -> Vec<ConstantType> {
@@ -268,6 +305,32 @@ impl ConstantType {
             ConstantType::U64 => "u64".to_string(),
         }
     }
+
+    /// Return the set of all primitives that can return this
+    /// type, along with the argument types for those primitives.
+    ///
+    /// A "None" value as an argument type means that the argument
+    /// type is unconstrained by the return type.
+    pub fn primitives_for(&self) -> Vec<(crate::ir::Primitive, Vec<Option<ConstantType>>)> {
+        use crate::ir::Primitive::*;
+
+        match self {
+            ConstantType::Void => vec![(Print, vec![None])],
+            ConstantType::I8 | ConstantType::I16 | ConstantType::I32 | ConstantType::I64 => vec![
+                (Plus, vec![Some(*self), Some(*self)]),
+                (Minus, vec![Some(*self), Some(*self)]),
+                (Times, vec![Some(*self), Some(*self)]),
+                (Divide, vec![Some(*self), Some(*self)]),
+                (Negate, vec![Some(*self)]),
+            ],
+            ConstantType::U8 | ConstantType::U16 | ConstantType::U32 | ConstantType::U64 => vec![
+                (Plus, vec![Some(*self), Some(*self)]),
+                (Minus, vec![Some(*self), Some(*self)]),
+                (Times, vec![Some(*self), Some(*self)]),
+                (Divide, vec![Some(*self), Some(*self)]),
+            ],
+        }
+    }
 }
 
 #[derive(Debug, Error, PartialEq)]

src/syntax/validate.rs

@@ -99,11 +99,8 @@ impl Program {
                 }
 
                 TopLevel::Structure(loc, name, fields) => {
-                    let definition = StructureDefinition::new(
-                        loc,
-                        name.clone(),
-                        fields.into_iter().map(|(n, t)| (n, Some(t))).collect(),
-                    );
+                    let definition =
+                        StructureDefinition::new(loc, name.clone(), fields.into_iter().collect());
 
                     structures.insert(name, definition);
                 }

src/type_infer/convert.rs

@@ -124,6 +124,14 @@ impl InferenceEngine {
             // converting values is mostly tedious, because there's so many cases
             // involved
             syntax::Expression::Value(loc, val) => match val {
+                syntax::Value::Void => (
+                    ir::Expression::Atomic(ir::ValueOrRef::Value(
+                        loc,
+                        ir::TypeOrVar::Primitive(PrimitiveType::Void),
+                        ir::Value::Void,
+                    )),
+                    ir::TypeOrVar::Primitive(PrimitiveType::Void),
+                ),
                 syntax::Value::Number(base, mctype, value) => {
                     let (newval, newtype) = match mctype {
                         None => {

src/util.rs

@@ -1,3 +1,4 @@
 pub mod pretty;
 pub mod scoped_map;
 pub mod warning_result;
+pub mod weighted_map;

src/util/weighted_map.rs

@@ -0,0 +1,21 @@
+use rand::distributions::{Distribution, WeightedIndex};
+
+pub struct WeightedMap<T: Clone> {
+    index: WeightedIndex<usize>,
+    items: Vec<T>,
+}
+
+impl<T: Clone> WeightedMap<T> {
+    pub fn new(map: &[(usize, T)]) -> Self {
+        let index = WeightedIndex::new(map.iter().map(|x| x.0)).unwrap();
+        let items = map.iter().map(|x| x.1.clone()).collect();
+        WeightedMap { index, items }
+    }
+}
+
+impl<T: Clone> Distribution<T> for WeightedMap<T> {
+    fn sample<R: rand::prelude::Rng + ?Sized>(&self, rng: &mut R) -> T {
+        let idx = self.index.sample(rng);
+        self.items.get(idx).unwrap().clone()
+    }
+}