From 0bd315a0101b0fe43f1cf80931d962d101b18f1d Mon Sep 17 00:00:00 2001
From: Joe Whitfield-Seed <joeseed86@gmail.com>
Date: Sun, 12 Mar 2017 23:37:21 +0000
Subject: [PATCH] WIP noImplicitAny

---
 src/node-types.ts | 12 +++++++++++
 src/unify.ts      | 52 ++++++++++++++++-------------------------------
 src/util.ts       | 11 ++++++++--
 3 files changed, 39 insertions(+), 36 deletions(-)

diff --git a/src/node-types.ts b/src/node-types.ts
index 7a0929a..9b1dcd3 100644
--- a/src/node-types.ts
+++ b/src/node-types.ts
@@ -156,6 +156,18 @@ export interface TypedIfNode extends AstIfNode, Typed {
   elseBranch: TypedNode
 }
 
+//
+// Nodes with shared traits
+//
+export type TypedLiteralNode = TypedStringNode | TypedBooleanNode | TypedNumeralNode
+
+//
+// Guard functions
+//
+export function isTypedLiteralNode (node: TypedNode): node is TypedLiteralNode {
+  return ['Bool', 'Str', 'Numeral'].includes(node.type)
+}
+
 //
 // Runtime values
 // TODO
diff --git a/src/unify.ts b/src/unify.ts
index 97ea0d6..3bc2ed7 100644
--- a/src/unify.ts
+++ b/src/unify.ts
@@ -1,13 +1,17 @@
 import PeachError from './errors'
 import { isArray, isEqual } from './array'
+import { zip } from './util'
+import { TypedNode, TypedLiteralNode, TypedDestructuredArrayNode, Value, isTypedLiteralNode } from './node-types'
+
+// FIXME tagged union - with didMatch: false, there are never bindings.
+type binding = { [name: string]: Value }
 
-// FIXME union type - with didMatch: false, there are never bindings.
 interface unification {
   didMatch: boolean,
-  bindings: object
+  bindings: binding
 }
 
-export default function unify (patterns, values) : unification {
+export default function unify (patterns: TypedNode[], values: Value[]): unification {
   if (patterns.length !== values.length) {
     return didNotMatch
   }
@@ -25,24 +29,23 @@ export default function unify (patterns, values) : unification {
   return didMatch(bindings)
 }
 
-function unifyOne (pattern, value) {
-  // TODO value equality operator
-  if (isValue(pattern) && pattern.value === value) {
+function unifyOne (pattern: TypedNode, value: Value): binding {
+  if (isTypedLiteralNode(pattern) && pattern.value === value) {
     // the pattern matched, but there is nothing to bind
     return {}
   }
 
-  if (isName(pattern)) {
+  if (pattern.type === 'Name') {
     // the pattern matched; return a new binding
     return { [pattern.name]: value }
   }
 
   // TODO generic value equality
-  if (isArray(pattern) && isEqual(pattern.values, value)) {
+  if (pattern.type === 'Array' && isEqual(pattern.values, value)) {
     return {}
   }
 
-  if (isDestructuredArray(pattern)) {
+  if (pattern.type === 'DestructuredArray') {
     return destructure(pattern, value)
   }
 
@@ -51,14 +54,14 @@ function unifyOne (pattern, value) {
 }
 
 // TODO this will need to change when Array is a wrapped type
-function destructure ({ head, tail }, array) {
-  if (array.length === 0) {
+function destructure ({ head, tail }: TypedDestructuredArrayNode, values: Value[]): binding {
+  if (values.length === 0) {
     throw new PeachError(`Empty arrays cannot be destructured because they don't have a head`)
   }
 
-  const boundHead = unifyOne(head, array[0])
+  const boundHead = unifyOne(head, values[0])
   if (boundHead !== null) {
-    const boundTail = unifyOne(tail, array.slice(1))
+    const boundTail = unifyOne(tail, values.slice(1))
     if (boundTail) {
       return Object.assign(boundHead, boundTail)
     }
@@ -67,33 +70,14 @@ function destructure ({ head, tail }, array) {
   return null
 }
 
-const didNotMatch : unification = {
+const didNotMatch: unification = {
   didMatch: false,
   bindings: {}
 }
 
-function didMatch (bindings) : unification {
+function didMatch (bindings: binding) : unification {
   return {
     didMatch: true,
     bindings
   }
 }
-
-// TODO these belong with type definitions
-function isName ({ type }) {
-  return type === 'Name'
-}
-
-function isValue ({ type }) {
-  return ['Bool', 'Str', 'Numeral'].includes(type)
-}
-
-function isDestructuredArray ({ type }) {
-  return type === 'DestructuredArray'
-}
-
-// TODO stdlib
-function zip (arrayA, arrayB) {
-  return arrayA.map((e, i) => [e, arrayB[i]])
-}
-
diff --git a/src/util.ts b/src/util.ts
index 3443ea2..bbf2b62 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -1,5 +1,5 @@
 // _.extend, but immutable by default
-export function extend (source, ...extensions) {
+export function extend (source: any, ...extensions: any[]) {
   return Object.assign({}, source, ...extensions)
 }
 
@@ -7,7 +7,7 @@ export const clone = extend
 
 // shortcut for creating an object with the given prototype and
 //  properties with default behaviour
-export function create (proto, properties = null) {
+export function create (proto: any, properties: any = null) {
   return Object.assign(Object.create(proto), properties)
 }
 
@@ -20,3 +20,10 @@ export function restAndLast<T> (arr: T[]): [T[], T] {
 export function last<T> (arr: T[]): T {
   return arr[arr.length - 1]
 }
+
+export function zip<A, B> (a: A[], b: B[]): [A, B][] {
+  return a.map((aValue, i): [A, B] => {
+    const bValue = b[i]
+    return [aValue, bValue]
+  })
+}