feat: transpile hello world view function

examples/single-page/script/generate_test_file

@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
 
 # generate a 10MB test file
-< /dev/urandom tr -dc "[:alnum:]" | head -c10000000 > file.txt
+< /dev/urandom tr -dc "[:alnum:]" | head -c10000000 > input.txt

examples/single-page/src/Main.elm

@@ -1,4 +1,4 @@
-module Main exposing (view, view2, view3, badReturnType)
+module Main exposing (view, view2, view3, view4, view5, badReturnType, true)
 
 import Html exposing (Html, div, text)
 import Svg exposing (Svg, svg)
@@ -36,6 +36,24 @@ view3 model =
         Nothing ->
             text "Failed to decode"
 
+view4 : String -> Html msg
+view4 model =
+    if model == "bar" then
+        div []
+            [ text <| "Hello world" ++ model ]
+    else
+        div []
+            [ text "Hello world" ]
+
+view5 : { t | x : String } -> Html msg
+view5 { x } =
+    div []
+        [ text x ]
+
 badReturnType : String -> Int
 badReturnType _ =
     42
+
+true : Bool
+true =
+    True

src/elm.rs

@@ -4,7 +4,7 @@ use std::collections::HashMap;
 use std::fs::{self, canonicalize, metadata};
 use std::io::{self, BufRead, Error, ErrorKind, Write};
 use std::path::{Path, PathBuf};
-use std::process::{Command};
+use std::process::Command;
 use tracing::info_span;
 
 pub fn make(file: &Path, debug: bool, verbosity: u64) -> Result<(), Problem> {
@@ -39,7 +39,9 @@ pub fn make(file: &Path, debug: bool, verbosity: u64) -> Result<(), Problem> {
     Ok(())
 }
 
-pub fn load_interfaces(elm_cache_dir: &Path) -> Result<HashMap<String, elmi::Interface>, Problem> {
+pub fn load_interfaces(
+    elm_cache_dir: &Path,
+) -> Result<HashMap<elmi::ModuleNameCanonical, elmi::Interface>, Problem> {
     let mut interfaces = HashMap::new();
 
     let entries = fs::read_dir(&elm_cache_dir)
@@ -51,6 +53,27 @@ pub fn load_interfaces(elm_cache_dir: &Path) -> Result<HashMap<String, elmi::Int
         })?;
         let path = entry.path();
         if path.is_file() {
+            match path.file_name() {
+                Some(file_name) if file_name == "i.dat" => {
+                    let data = std::fs::read(&path)
+                        .map_err(|io_err| CompilerError::ReadInputFailed(io_err, path.clone()))?;
+
+                    let (_remaining, i) = <elmi::Interfaces as elmi::DataBinary>::get(&data)
+                        .map_err(|_err| {
+                            CompilerError::FailedElmiParse("todo elmi parsing".to_owned())
+                        })?;
+
+                    for (module_name, dep_interface) in i.into_iter() {
+                        match dep_interface {
+                            elmi::DependencyInterface::Public(interface) => {
+                                interfaces.insert(module_name, interface);
+                            }
+                            _ => {}
+                        }
+                    }
+                }
+                _ => {}
+            }
             match path.extension() {
                 Some(ext) if ext == "elmi" => {
                     // step 4 load all the modules
@@ -70,12 +93,16 @@ pub fn load_interfaces(elm_cache_dir: &Path) -> Result<HashMap<String, elmi::Int
                     if let Some(stem) = path.file_stem() {
                         // in theory the module name of the interface can be determined by
                         // the filename in elm 0.19.0 and 0.19.1
-                        let module_name: String = stem
+                        let module: String = stem
                             .to_string_lossy()
                             .split('-')
                             .collect::<Vec<&str>>()
                             .join(".");
-                        interfaces.insert(module_name, i);
+                        let cannonical_module = elmi::ModuleNameCanonical {
+                            package: elmi::PackageName::new("author", "project"),
+                            module: elmi::Name(module),
+                        };
+                        interfaces.insert(cannonical_module, i);
                     }
                 }
                 _ => (),
@@ -103,13 +130,14 @@ pub fn load_objects(elm_cache_dir: &Path) -> Result<HashMap<elmi::Global, elmi::
                     let data = std::fs::read(&path)
                         .map_err(|io_err| CompilerError::ReadInputFailed(io_err, path.clone()))?;
 
-                    let (_remaining, opt_global_graph) = elmi::OptGlobalGraph::get(&data).map_err(|_err| {
+                    let (_remaining, opt_global_graph) =
-                        CompilerError::FailedElmiParse("todo elmi parsing".to_owned())
+                        elmi::OptGlobalGraph::get(&data).map_err(|_err| {
-                    })?;
+                            CompilerError::FailedElmiParse("todo elmi parsing".to_owned())
+                        })?;
 
                     objects.extend(opt_global_graph.nodes.into_iter());
                 }
-                _ => {},
+                _ => {}
             }
             match path.extension() {
                 Some(ext) if ext == "elmo" => {
@@ -123,9 +151,10 @@ pub fn load_objects(elm_cache_dir: &Path) -> Result<HashMap<elmi::Global, elmi::
                         .map_err(|io_err| CompilerError::ReadInputFailed(io_err, path.clone()))?;
                     drop(load_guard);
 
-                    let (_remaining, opt_local_graph) = elmi::OptLocalGraph::get(&data).map_err(|_err| {
+                    let (_remaining, opt_local_graph) =
-                        CompilerError::FailedElmiParse("todo elmi parsing".to_owned())
+                        elmi::OptLocalGraph::get(&data).map_err(|_err| {
-                    })?;
+                            CompilerError::FailedElmiParse("todo elmi parsing".to_owned())
+                        })?;
 
                     objects.extend(opt_local_graph.nodes.into_iter());
                 }

src/main.rs

@@ -2,7 +2,6 @@ extern crate naive_wadler_prettier as pretty;
 use crate::reporting::{CompilerError, InterpreterError, Problem, SetupError, TypeError};
 use crate::timings::Timings;
 use elm_project_utils::ChecksumConstraint;
-use elmi::DataBinary;
 use os_pipe::dup_stderr;
 use pretty::pretty;
 use serde::{Deserialize, Serialize};
@@ -115,7 +114,14 @@ fn exec(
     let source_checksum = hasher.finish();
 
     // step 2.5 get the module name out of the file.
-    let elmi::Name(target_module) = elm::parse_module_name(&data)?;
+
+    let entrypoint = elmi::Global(
+        elmi::ModuleNameCanonical {
+            package: elmi::PackageName::new("author", "project"),
+            module: elm::parse_module_name(&data)?,
+        },
+        elmi::Name(function.clone()),
+    );
 
     // step 3 find all the filepaths in the elm-stuff/0.19.1/* folder
     let interfaces = elm::load_interfaces(&elm_cache_dir)?;
@@ -123,16 +129,16 @@ fn exec(
     // Step 5, check for the desired function
     let span = info_span!("resolved target function");
     let timing_guard = span.enter();
-    let (input_type, output_type) = match interfaces.get(&target_module) {
+    let (input_type, output_type) = match interfaces.get(&entrypoint.0) {
-        Some(interface) => match interface.values.get(&elmi::Name::from(&function)) {
+        Some(interface) => match interface.values.get(&entrypoint.1) {
             Some(annotation) => {
                 let elmi::CannonicalAnnotation(_free_vars, tipe) = annotation;
 
                 resolve_function_type(tipe)?
             }
-            None => return Err(CompilerError::BadImport(target_module, function).into()),
+            None => return Err(CompilerError::BadImport(entrypoint).into()),
         },
-        None => return Err(CompilerError::MissingModuleTypeInformation(target_module).into()),
+        None => return Err(CompilerError::MissingModuleTypeInformation(entrypoint.0).into()),
     };
     drop(timing_guard);
 
@@ -144,8 +150,8 @@ fn exec(
     let timing_guard = span.enter();
     let (gen_module_name, source) = fixture::generate(
         source_checksum,
-        target_module,
+        entrypoint.0.module.clone(),
-        function,
+        entrypoint.1.clone(),
         input_type,
         output_type,
     );

src/reporting.rs

@@ -1,3 +1,4 @@
+use crate::reporting::doc::reflow;
 use deno_core::error::AnyError;
 use elm_project_utils::RedoScriptError;
 use elmi;
@@ -89,8 +90,8 @@ pub enum CompilerError {
     MissingElmStuff(PathBuf),
     CantParseModule(String), // first line
     EmptyModule,
-    MissingModuleTypeInformation(String),
+    MissingModuleTypeInformation(elmi::ModuleNameCanonical),
-    BadImport(String, String),
+    BadImport(elmi::Global),
     FailedBuildingFixture,
     ReadInputFailed(io::Error, PathBuf),
     WriteOutputFailed(io::Error, PathBuf),
@@ -147,9 +148,9 @@ impl CompilerError {
             CantParseModule(_first_line_prefix) => Doc::text("todo could not parse module"),
             EmptyModule => Doc::text("I did not expect the module file to be empty"),
             MissingModuleTypeInformation(_) => Doc::text("todo missing module type information"),
-            BadImport(module, symbol) => {
+            BadImport(elmi::Global(module, symbol)) => {
                 // TODO suggest alternatives using edit distance
-                Doc::text(format!(
+                reflow(format!(
                     "The `{}` module does not expose `{}`",
                     module, symbol
                 ))

src/transpile.rs

@@ -1,9 +1,11 @@
-use crate::reporting::{CompilerError, Problem, TypeError};
-use elmi::DataBinary;
-use std::collections::HashMap;
-use std::path::{PathBuf};
-use tracing::info_span;
 use crate::elm;
+use crate::reporting::{CompilerError, Problem, TypeError};
+use genco::lang::rust;
+use genco::tokens::quoted;
+use genco::{quote, quote_in};
+use std::collections::{HashMap, HashSet};
+use std::path::PathBuf;
+use tracing::info_span;
 
 pub fn transpile(
     file: PathBuf,
@@ -36,22 +38,32 @@ pub fn transpile(
     // used in the project. So I would want to reduce the tuples of file function into a set of
     // files to load. Then recursively load all dependencies.
 
+    let entrypoint = elmi::Global(
+        elmi::ModuleNameCanonical {
+            package: elmi::PackageName::new("author", "project"),
+            module: elmi::Name(target_module.clone()),
+        },
+        elmi::Name(function.clone()),
+    );
+
     // step 3 find all the filepaths in the elm-stuff/0.19.1/* folder
     let interfaces = elm::load_interfaces(&elm_cache_dir)?;
 
     // Step 4, check for the desired functions have types that we can compile.
     let span = info_span!("resolved target function");
     let timing_guard = span.enter();
-    match interfaces.get(&target_module) {
+    let signature = match interfaces.get(&entrypoint.0) {
         Some(interface) => match interface.values.get(&elmi::Name::from(&function)) {
             Some(annotation) => {
-                let elmi::CannonicalAnnotation(_free_vars, tipe) = annotation;
+                let elmi::CannonicalAnnotation(_free_vars, ref tipe) = annotation;
 
-                validate_function_type(tipe)?
+                validate_function_type(tipe)?;
+
+                annotation
             }
-            None => return Err(CompilerError::BadImport(target_module, function).into()),
+            None => return Err(CompilerError::BadImport(entrypoint).into()),
         },
-        None => return Err(CompilerError::MissingModuleTypeInformation(target_module).into()),
+        None => return Err(CompilerError::MissingModuleTypeInformation(entrypoint.0).into()),
     };
     drop(timing_guard);
 
@@ -63,74 +75,98 @@ pub fn transpile(
 
     let objects = elm::load_objects(&elm_cache_dir)?;
 
-    let entrypoint = elmi::Global(
+    if let Some(node) = objects.get(&entrypoint) {
-        elmi::ModuleNameCanonical {
+        match node {
-            package: elmi::PackageName::new("author", "project"),
+            elmi::Node::Define(elmi::Expr::Function(ref parameters, ref body), deps) => {
-            module: elmi::Name(target_module.clone()),
+                for dep in deps {
-        },
+                    println!("I depend on {}", dep);
-        elmi::Name(function.clone()),
+                }
-    );
+                let elmi::CannonicalAnnotation(elmi::FreeVars(free_variables), tipe) = signature;
 
-    println!("the artifacts has the symbol {}", objects.contains_key(&entrypoint));
+                let (parameter_types, return_type) =
+                    extract_function_types(&tipe, parameters.len()).unwrap();
+
+                let xs = parameters
+                    .into_iter()
+                    .zip(parameter_types.into_iter())
+                    .collect::<Vec<_>>();
+                    
+                // TODO add any TLambdas in the signature to the type parameters of the functions
+                // as where bounds
+
+                let mut tokens = rust::Tokens::new();
+                codegen_function(
+                    &mut tokens,
+                    &entrypoint.1,
+                    &free_variables,
+                    &xs,
+                    return_type,
+                    body,
+                );
+                println!("{}", tokens.to_file_string().unwrap());
+            }
+            _ => println!("I don't know how to transpile that node"),
+        }
+    }
+    println!("total symbols {}", objects.len());
     //let visited: HashSet<Global> = HashSet::new();
-    for (_key, node) in objects.iter() {
+    for (key, node) in objects.iter() {
         //println!("key {}", key);
-       	match node {
+        match node {
-			elmi::Node::Define(_expr, deps) => {
+            elmi::Node::Define(expr, deps) => {
-				for dep in deps.iter() {
+                //println!("key => {:?}", expr);
-					if !objects.contains_key(&dep) {
+                for dep in deps.iter() {
+                    if !objects.contains_key(&dep) {
                         println!("could not find dep {}", dep);
                     }
-				}
+                }
-			}
+                break;
-			elmi::Node::DefineTailFunc(_, _, deps) => {
+            }
-				for dep in deps.iter() {
+            elmi::Node::DefineTailFunc(_, _, deps) => {
-					if !objects.contains_key(&dep) {
+                for dep in deps.iter() {
+                    if !objects.contains_key(&dep) {
                         println!("could not find dep {}", dep);
                     }
-				}
+                }
-			}
+            }
-			elmi::Node::Ctor(_, _) => {
+            elmi::Node::Ctor(_, _) => {}
-			}
+            elmi::Node::Enum(_) => {}
-			elmi::Node::Enum(_) => {
+            elmi::Node::Box => {}
-			}
+            elmi::Node::Link(dep) => {
-			elmi::Node::Box => {
-			}
-			elmi::Node::Link(dep) => {
                 if !objects.contains_key(&dep) {
                     println!("could not find dep {}", dep);
                 }
-			}
+            }
-			elmi::Node::Cycle(_, _, _, deps) => {
+            elmi::Node::Cycle(_, _, _, deps) => {
-				for dep in deps.iter() {
+                for dep in deps.iter() {
                     if !objects.contains_key(&dep) {
                         println!("could not find dep {}", dep);
                     }
-				}
+                }
-			}
+            }
-			elmi::Node::Manager(_) => (),
+            elmi::Node::Manager(_) => (),
-			elmi::Node::Kernel(_, deps) => {
+            elmi::Node::Kernel(_, deps) => {
-				for dep in deps.iter() {
+                for dep in deps.iter() {
                     if !objects.contains_key(&dep) {
                         println!("could not find dep {}", dep);
                     }
-				}
+                }
-			}
+            }
-			elmi::Node::PortIncoming(_, deps) => {
+            elmi::Node::PortIncoming(_, deps) => {
-				for dep in deps.iter() {
+                for dep in deps.iter() {
                     if !objects.contains_key(&dep) {
                         println!("could not find dep {}", dep);
                     }
-				}
+                }
-			}
+            }
-			elmi::Node::PortOutgoing(_, deps) => {
+            elmi::Node::PortOutgoing(_, deps) => {
-				for dep in deps.iter() {
+                for dep in deps.iter() {
                     if !objects.contains_key(&dep) {
                         println!("could not find dep {}", dep);
                     }
-				}
+                }
-			}
+            }
-		}
+        }
     }
 
     let _symbol_table: HashMap<elmi::Global, elmi::Node> = HashMap::new();
@@ -217,6 +253,7 @@ fn validate_input_type(tipe: &elmi::Type) -> Result<(), TypeError> {
             elmi::AliasType::Filled(tipe) => validate_input_type(tipe),
             elmi::AliasType::Holey(_) => Err(TypeError::CantEvalHoleyAlias),
         },
+        elmi::Type::TRecord(_, _) => Ok(()),
         _ => Err(TypeError::OutputTypeNotSupported(tipe.clone())),
     }
 }
@@ -244,6 +281,219 @@ fn validate_output_type(tipe: &elmi::Type) -> Result<(), TypeError> {
     }
 }
 
+fn codegen_function(
+    tokens: &mut rust::Tokens,
+    name: &elmi::Name,
+    type_variables: &HashSet<elmi::Name>,
+    parameters: &[(&elmi::Name, elmi::Type)],
+    return_type: elmi::Type,
+    body: &elmi::Expr,
+) {
+    quote_in! { *tokens =>
+        fn #(&name.0)#(if !type_variables.is_empty() =>
+            <#(for elmi::Name(ref tvar) in type_variables.iter() join (, ) =>
+                #tvar
+            )>
+        )(#(for (elmi::Name(ref parameter), tipe) in parameters.iter() join (, ) =>
+            #parameter: #(ref out { codegen_type(out, tipe) })
+        )) -> #(ref out { codegen_type(out, &return_type) }) {
+            #(ref out { codegen_expr(out, body) })
+        }
+    }
+}
+
+fn codegen_type(tokens: &mut rust::Tokens, tipe: &elmi::Type) {
+    quote_in! { *tokens =>
+        #(match tipe {
+            elmi::Type::TLambda(a, b) => {
+                ( #(ref out => codegen_type(out, a) ) -> #(ref out => codegen_type(out, b) ) )
+            }
+            elmi::Type::TVar(elmi::Name(variable)) => {
+                #variable
+            },
+            elmi::Type::TType(module_name, name, args) if module_name == "elm/core/String" && name == "String" && args.is_empty() => {
+                String
+            }
+            elmi::Type::TType(home, name, args) if args.is_empty() => {
+                #(ref out => codegen_name_from_global(out, home, name))
+            }
+            elmi::Type::TType(home, name, args) => {
+                #(ref out => codegen_name_from_global(out, home, name))<#(for arg in args join(, ) =>
+                    #(ref out => codegen_type(out, arg))
+                )>
+            }
+            //    // Might be a primitive type
+            //    #(if module_name == "elm/core/String" && name == "String" => String)
+            //    #(if module_name == "elm/core/Basics" && name == "Int" => i64)
+            //    #(if module_name == "elm/core/Basics" && name == "Float" => f64)
+            //    #(if module_name == "elm/core/Basics" && name == "Bool" => bool)
+            //    #(if module_name == "elm/core/Maybe" && name == "Maybe" => Option<i32>)
+            //    #(if module_name == "elm/bytes/Bytes" && name == "Bytes" => Vec<u8>)
+            //}
+            //elmi::Type::TType(_, _, _) => Err(TypeError::CantEvalCustomType),
+            //elmi::Type::TRecord(_, _) => Err(TypeError::CantEvalRecord),
+            elmi::Type::TUnit => (),
+            _ => {
+                println!("failed to solve code {:?}", tipe);
+                todo_tipe
+            },
+            //elmi::Type::TTuple(_, _, _) => Err(TypeError::CantEvalTuple),
+            //elmi::Type::TAlias(_, _, _, ref alias) => {
+            //    match &**alias {
+            //        elmi::AliasType::Filled(tipe) => {
+            //            // I think the recursion is limited to a single step. I have not tested what
+            //            // the CannonicalAnnotation would look like for a doubly indirect alias, for
+            //            // example for `view` below
+            //            // ```elm
+            //            // type alias Foo = Int
+            //            // type alias Bar = String
+            //            //
+            //            // type alias Zap = Foo -> Bar
+            //            //
+            //            // view : Zap
+            //            // ```
+            //            validate_function_type(tipe)
+            //        }
+            //        elmi::AliasType::Holey(_) => return Err(TypeError::CantEvalHoleyAlias),
+            //    }
+            //}
+        })
+    };
+}
+
+fn codegen_name_from_global(
+    tokens: &mut rust::Tokens,
+    home: &elmi::ModuleNameCanonical,
+    name: &elmi::Name,
+) {
+    quote_in! { *tokens =>
+        #(ref out => codegen_home_to_builder(out, home) )__#(&name.0)
+    }
+}
+
+fn codegen_home_to_builder(tokens: &mut rust::Tokens, global: &elmi::ModuleNameCanonical) {
+    let elmi::ModuleNameCanonical {
+        package: elmi::PackageName { author, project },
+        module: home,
+    } = global;
+
+    quote_in! { *tokens =>
+        _#(author.replace("-", "_"))_#(project.replace("-", "_"))__#(home.0.replace(".", "_"))
+    }
+}
+
+fn codegen_expr(tokens: &mut rust::Tokens, expr: &elmi::Expr) {
+    match expr {
+        elmi::Expr::Bool(true) => quote_in! { *tokens => true },
+        elmi::Expr::Bool(false) => quote_in! { *tokens => false },
+        elmi::Expr::Chr(c) => quote_in! { *tokens => #("'")#c#("'") },
+        elmi::Expr::Str(s) => quote_in! { *tokens => #(quoted(s)) },
+        elmi::Expr::Int(x) => quote_in! { *tokens => #(x.to_string()) },
+        elmi::Expr::Float(x) => quote_in! { *tokens => #(x.to_string()) },
+        elmi::Expr::VarLocal(elmi::Name(ref name)) => {
+            quote_in! { *tokens =>
+                #name
+            }
+        }
+        elmi::Expr::VarGlobal(elmi::Global(home, name)) => {
+            quote_in! { *tokens =>
+                #(ref out => codegen_name_from_global(out, home, name))
+            }
+        }
+        //elmi::Expr::VarEnum(Global, IndexZeroBased),
+        //elmi::Expr::VarBox(Global),
+        //elmi::Expr::VarCycle(ModuleNameCanonical, Name),
+        //elmi::Expr::VarDebug(Name, ModuleNameCanonical, AnnotationRegion, Option<Name>),
+        //elmi::Expr::VarKernel(Name, Name),
+        elmi::Expr::List(xs) => {
+            if xs.is_empty() {
+                quote_in! { *tokens => &[] }
+            } else {
+                quote_in! { *tokens =>
+                    &[
+                        #(for x in xs join (,#<push>) => #(ref out => codegen_expr(out, x) ) )
+                    ]
+                }
+            }
+        }
+        elmi::Expr::Function(parameters, body) => {
+            quote_in! { *tokens =>
+                "i don't know how to code gen a function expression"
+                //#(for elmi::Name(ref parameter) in parameters.iter() join (, ) =>
+                //)
+            }
+        }
+        elmi::Expr::Call(ref fexpr, args) => {
+            quote_in! { *tokens =>
+                #(match &**fexpr {
+                    elmi::Expr::VarGlobal(elmi::Global(home, name)) => {
+                        #(ref out => codegen_name_from_global(out, home, name))
+                    }
+                    _ => {
+                        "unknown"
+                    }
+                })(
+                    #(for arg in args join (,#<push>) => #(ref out =>
+                            codegen_expr(out, arg) )
+                    )
+                )
+            }
+        }
+        //elmi::Expr::TailCall(Name, Vec<(Name, Expr)>),
+        //elmi::Expr::If(Vec<(Expr, Expr)>, Box<Expr>),
+        //elmi::Expr::Let(Def, Box<Expr>),
+        //elmi::Expr::Destruct(Destructor, Box<Expr>),
+        //elmi::Expr::Case(Name, Name, Decider<Choice>, Vec<(i64, Expr)>),
+        //elmi::Expr::Accessor(Name),
+        //elmi::Expr::Access(Box<Expr>, Name),
+        //elmi::Expr::Update(Box<Expr>, HashMap<Name, Expr>),
+        //elmi::Expr::Record(HashMap<Name, Expr>),
+        elmi::Expr::Unit => (),
+        elmi::Expr::Tuple(a, b, None) => {
+            quote_in! { *tokens =>
+                ( #(ref out => codegen_expr(out, a) ), #(ref out => codegen_expr(out, b) ) )
+            }
+        }
+        elmi::Expr::Tuple(a, b, Some(c)) => {
+            quote_in! { *tokens =>
+                ( #(ref out => codegen_expr(out, a) ), #(ref out => codegen_expr(out, b) ), #(ref out => codegen_expr(out, c) ) )
+            }
+        }
+        //elmi::Expr::Shader(ShaderSource, HashSet<Name>, HashSet<Name>),
+        _ => quote_in! { *tokens => #(format!("{:?}", expr)) },
+    }
+}
+
+fn extract_function_types(
+    mut tipe: &elmi::Type,
+    mut nargs: usize,
+) -> Option<(Vec<elmi::Type>, elmi::Type)> {
+    let mut parameters = Vec::with_capacity(nargs);
+    loop {
+        if nargs == 0 {
+            return Some((parameters, tipe.clone()));
+        }
+        match tipe {
+            elmi::Type::TLambda(a, b) => {
+                parameters.push(reduce_alias_types(&*a).clone());
+                tipe = reduce_alias_types(&*b);
+                nargs -= 1;
+            }
+            _ => return None,
+        }
+    }
+}
+
+fn reduce_alias_types(a: &elmi::Type) -> &elmi::Type {
+    match a {
+        elmi::Type::TAlias(_, _, _, ref alias) => match &**alias {
+            elmi::AliasType::Filled(b) => &b,
+            elmi::AliasType::Holey(_) => a,
+        },
+        _ => a,
+    }
+}
+
 // Figure out how to do structural types. If I could name mangle all the functions I could write
 // them out in the same namespace as lambdas which would avoid the structural typing problem if the
 // lambda was used by one type. Monomorphism. But if the lambda is used by multiple types then I