wip: ditto-type-checker

Cargo.toml

@@ -11,4 +11,5 @@ members = [
   "crates/ditto-tree-sitter",
   "crates/ditto-highlight",
   "crates/ditto-pattern-checker",
+  "crates/ditto-type-checker",
 ]

crates/ditto-ast/src/utils.rs

@@ -114,14 +114,38 @@ impl Type {
                 canonical_value,
                 source_value: _,
                 alias_variables: _,
-                aliased_type: _,
+                aliased_type,
                 constructor_kind: _,
             } => {
-                write!(w, "{canonical_value}")
+                write!(w, "{canonical_value} / ")?;
+                aliased_type.debug_render_to(w)
             }
             Self::PrimConstructor(prim) => {
                 write!(w, "{prim}")
             }
+
+            Self::Call {
+                function:
+                    box Self::ConstructorAlias {
+                        canonical_value,
+                        source_value: _,
+                        alias_variables: _,
+                        aliased_type,
+                        constructor_kind: _,
+                    },
+                arguments,
+            } => {
+                write!(w, "{canonical_value}(")?;
+                let arguments_len = arguments.len();
+                for (i, arg) in arguments.iter().enumerate() {
+                    arg.debug_render_to(w)?;
+                    if i + 1 != arguments_len {
+                        write!(w, ", ")?;
+                    }
+                }
+                write!(w, ") / ")?;
+                aliased_type.debug_render_to(w)
+            }
             Self::Call {
                 function,
                 arguments,

crates/ditto-type-checker/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "ditto-type-checker"
+version = "0.0.1"
+edition = "2021"
+license = "BSD-3-Clause"
+
+[lib]
+doctest = false
+
+[dependencies]
+ditto-cst = { path = "../ditto-cst" }
+ditto-ast = { path = "../ditto-ast" }
+ditto-pattern-checker = { path = "../ditto-pattern-checker" }
+nonempty = "0.8"
+smallvec = "1.0"
+smol_str = "0.1"
+halfbrown = "0.1"
+indexmap = "1.9"
+serde = { version = "1.0", features = ["derive"] }
+miette = { version = "5.5", features = ["fancy"] }
+thiserror = "1.0"
+Inflector = "0.11.4"
+tracing = "0.1"
+tinyset = "0.4"
+
+[dev-dependencies]
+datadriven = "0.6"

crates/ditto-type-checker/README.md

@@ -0,0 +1,8 @@
+# The ditto type checker
+
+This crate handles type-checking and linting the ditto syntax.
+
+The type-checking algorithm is based on [@david-christiansen](https://github.com/david-christiansen)'s [Bidirectional Typing Rules][bidirectional].
+
+[bidirectional]: https://www.davidchristiansen.dk/tutorials/bidirectional.pdf
+[bidirectional impl]: https://github.com/luc-tielen/typesystem