From 64bd12bd5e06306f4cfc7abce5a428dc60d41669 Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Wed, 7 Jun 2017 17:11:02 -0700
Subject: [PATCH 1/7] Pattern Matching WIP

---
 src/index.js                                  | 197 +++++++++++++++++-
 .../match/basic-placeholder/actual.js         |   7 +
 .../match/basic-placeholder/expected.js       |  13 ++
 test/fixtures/match/basic-statement/actual.js |   7 +
 .../match/basic-statement/expected.js         |   7 +
 .../match/basic-value-checks/actual.js        |   7 +
 .../match/basic-value-checks/expected.js      |  13 ++
 test/fixtures/match/basic/actual.js           |   7 +
 test/fixtures/match/basic/expected.js         |   9 +
 test/fixtures/match/no-else/actual.js         |   5 +
 test/fixtures/match/no-else/expected.js       |   5 +
 .../fixtures/match/single-else-expr/actual.js |   4 +
 .../match/single-else-expr/expected.js        |   6 +
 .../fixtures/match/single-else-stmt/actual.js |   4 +
 .../match/single-else-stmt/expected.js        |   4 +
 15 files changed, 291 insertions(+), 4 deletions(-)
 create mode 100644 test/fixtures/match/basic-placeholder/actual.js
 create mode 100644 test/fixtures/match/basic-placeholder/expected.js
 create mode 100644 test/fixtures/match/basic-statement/actual.js
 create mode 100644 test/fixtures/match/basic-statement/expected.js
 create mode 100644 test/fixtures/match/basic-value-checks/actual.js
 create mode 100644 test/fixtures/match/basic-value-checks/expected.js
 create mode 100644 test/fixtures/match/basic/actual.js
 create mode 100644 test/fixtures/match/basic/expected.js
 create mode 100644 test/fixtures/match/no-else/actual.js
 create mode 100644 test/fixtures/match/no-else/expected.js
 create mode 100644 test/fixtures/match/single-else-expr/actual.js
 create mode 100644 test/fixtures/match/single-else-expr/expected.js
 create mode 100644 test/fixtures/match/single-else-stmt/actual.js
 create mode 100644 test/fixtures/match/single-else-stmt/expected.js

diff --git a/src/index.js b/src/index.js
index a109a62..5365e68 100644
--- a/src/index.js
+++ b/src/index.js
@@ -255,9 +255,9 @@ export default function (babel) {
     return body;
   }
 
-  function ensureBlockBody(path) {
-    if (!t.isBlockStatement(path.node.body)) {
-      path.get("body").replaceWith(t.blockStatement([path.node.body]));
+  function ensureBlockBody(path, bodyKey = "body") {
+    if (!path.get(bodyKey).isBlockStatement()) {
+      path.get(bodyKey).replaceWith(t.blockStatement([path.node[bodyKey]]));
     }
   }
 
@@ -663,7 +663,7 @@ export default function (babel) {
     }
   }
 
-  function generateForInIterator (path, type: "array" | "object") {
+  function generateForInIterator(path, type: "array" | "object") {
     const idx = path.node.idx || path.scope.generateUidIdentifier("i");
     const len = path.scope.generateUidIdentifier("len");
 
@@ -758,6 +758,117 @@ export default function (babel) {
     return t.forStatement(init, test, update, path.node.body);
   }
 
+  function addAlternateToIfChain(rootIf, alternate) {
+    let tail = rootIf
+    while (tail.alternate) tail = tail.alternate;
+    tail.alternate = alternate;
+    return rootIf;
+  }
+
+  function isUndefined(path) {
+    return path.isIdentifier() && path.node.name === "undefined";
+  }
+
+  function isSignedNumber(path) {
+    return path.isUnaryExpression() &&
+      path.get("argument").isNumericLiteral() &&
+      (path.node.operator === "+" || path.node.operator === "-");
+  }
+
+  function looksLikeClassName(path) {
+    // disallow Foo.Bar for now.
+    if (!path.isIdentifier()) return false;
+    const { name } = path.node;
+    if (name[0].toUpperCase() === name[0]) {
+      // A -> true
+      if (name.length === 1) return true;
+      // ABC -> false, it's a constant
+      if (name.toUpperCase() === name) return false;
+      // Abc -> true
+      return true;
+    }
+    return false;
+  }
+
+  function isPrimitiveClass({ node: { name }}) {
+    switch (name) {
+      case "Number":
+      case "String":
+      case "Boolean":
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  function transformMatchCaseTest(path, argRef) {
+    if (path.isLogicalExpression()) {
+      transformMatchCaseTest(path.get("left"), argRef);
+      transformMatchCaseTest(path.get("right"), argRef);
+    } else if (path.isUnaryExpression() && path.node.operator === "!") {
+      transformMatchCaseTest(path.get("argument"), argRef);
+    } else if (path.isRegExpLiteral()) {
+      const testCall = t.callExpression(
+        t.memberExpression(path.node, t.identifier("test")),
+        [argRef]
+      );
+      path.replaceWith(testCall);
+    } else if (looksLikeClassName(path)) {
+      const classInstanceCheck = isPrimitiveClass(path)
+        ? t.binaryExpression("===",
+            t.unaryExpression("typeof", argRef),
+            t.stringLiteral(path.node.name.toLowerCase())
+          )
+        : t.binaryExpression("instanceof", argRef, path.node)
+      path.replaceWith(classInstanceCheck);
+    } else if (path.isLiteral() || isUndefined(path) || isSignedNumber(path)) {
+      const isEq = t.binaryExpression("===", argRef, path.node);
+      path.replaceWith(isEq);
+    }
+  }
+
+  function transformMatchCases(argRef, cases) {
+    return cases.reduce((rootIf, path) => {
+
+      // fill in placeholders
+      path.get("test").traverse({
+        PlaceholderExpression(placeholderPath) {
+          placeholderPath.replaceWith(argRef);
+        }
+      });
+
+      // add in ===, etc
+      transformMatchCaseTest(path.get("test"), argRef);
+
+      // add binding (and always use block bodies)
+      ensureBlockBody(path, "consequent");
+      if (path.node.binding) {
+        const bindingDecl = t.variableDeclaration("const", [
+          t.variableDeclarator(path.node.binding, argRef)
+        ]);
+        path.get("consequent").unshiftContainer("body", bindingDecl);
+      }
+
+      // handle `else`
+      if (path.node.test.type === "MatchElse") {
+        if (rootIf) {
+          return addAlternateToIfChain(rootIf, path.node.consequent);
+        } else {
+          // single match case with "else", weird. Just generate an anonymous block for now.
+          return path.node.consequent;
+        }
+      }
+
+      // generate `if` and append to if-else chain
+      const ifStmt = t.ifStatement(path.node.test, path.node.consequent);
+      if (!rootIf) {
+        return ifStmt;
+      } else {
+        return addAlternateToIfChain(rootIf, ifStmt);
+      }
+    }, null);
+  }
+
   // TYPE DEFINITIONS
   definePluginType("ForInArrayStatement", {
     visitor: ["idx", "elem", "array", "body"],
@@ -960,6 +1071,55 @@ export default function (babel) {
     aliases: ["MemberExpression", "Expression", "LVal"],
   });
 
+  definePluginType("MatchExpression", {
+    builder: ["discriminant", "cases"],
+    visitor: ["discriminant", "cases"],
+    aliases: ["Expression", "Conditional"],
+    fields: {
+      discriminant: {
+        validate: assertNodeType("Expression")
+      },
+      cases: {
+        validate: chain(assertValueType("array"), assertEach(assertNodeType("MatchCase")))
+      }
+    }
+  });
+
+  definePluginType("MatchStatement", {
+    builder: ["discriminant", "cases"],
+    visitor: ["discriminant", "cases"],
+    aliases: ["Statement", "Conditional"],
+    fields: {
+      discriminant: {
+        validate: assertNodeType("Expression")
+      },
+      cases: {
+        validate: chain(assertValueType("array"), assertEach(assertNodeType("MatchCase")))
+      }
+    }
+  });
+
+  definePluginType("MatchCase", {
+    builder: ["test", "consequent", "functional"],
+    visitor: ["test", "consequent"],
+    fields: {
+      test: {
+        validate: assertNodeType("Expression", "MatchElse")
+      },
+      consequent: {
+        validate: assertNodeType("BlockStatement", "ExpressionStatement")
+      }
+    }
+  });
+
+  definePluginType("MatchElse", {
+    // only allowed in MatchCase, so don't alias to Expression
+  });
+
+  definePluginType("PlaceholderExpression", {
+    aliases: ["Expression"]
+  });
+
   // traverse as top-level item so as to run before other babel plugins
   // (and avoid traversing any of their output)
   function Program(path, state) {
@@ -1258,6 +1418,35 @@ export default function (babel) {
         }
       },
 
+      MatchExpression(path) {
+        const { discriminant } = path.node;
+
+        const argRef = path.scope.generateUidIdentifier("it");
+        const matchBody = transformMatchCases(argRef, path.get("cases"));
+
+        const iife = t.callExpression(
+          t.arrowFunctionExpression([argRef], t.blockStatement([matchBody])),
+          [discriminant]
+        );
+        path.replaceWith(iife);
+      },
+
+      MatchStatement(path) {
+        const { discriminant } = path.node;
+
+        let argRef;
+        if (t.isIdentifier(discriminant)) {
+          argRef = discriminant;
+        } else {
+          argRef = path.scope.generateUidIdentifier("it");
+          path.insertBefore(t.variableDeclaration("const", [
+            t.variableDeclarator(argRef, discriminant)
+          ]));
+        }
+
+        const matchBody = transformMatchCases(argRef, path.get("cases"));
+        path.replaceWith(matchBody);
+      },
 
     });
 
diff --git a/test/fixtures/match/basic-placeholder/actual.js b/test/fixtures/match/basic-placeholder/actual.js
new file mode 100644
index 0000000..61c0908
--- /dev/null
+++ b/test/fixtures/match/basic-placeholder/actual.js
@@ -0,0 +1,7 @@
+match x:
+  | < 1: "lt one"
+  | + 1 == 1: "eq zero"
+  | == 2: "eq two"
+  | ~f(): "f(x) truthy"
+  | .prop: "has prop"
+  | .0: "has first child"
diff --git a/test/fixtures/match/basic-placeholder/expected.js b/test/fixtures/match/basic-placeholder/expected.js
new file mode 100644
index 0000000..d0d1511
--- /dev/null
+++ b/test/fixtures/match/basic-placeholder/expected.js
@@ -0,0 +1,13 @@
+if (x < 1) {
+    "lt one";
+  } else if (x + 1 === 1) {
+    "eq zero";
+  } else if (x === 2) {
+    "eq two";
+  } else if (f(x)) {
+    "f(x) truthy";
+  } else if (x.prop) {
+    "has prop";
+  } else if (x[0]) {
+    "has first child";
+  }
diff --git a/test/fixtures/match/basic-statement/actual.js b/test/fixtures/match/basic-statement/actual.js
new file mode 100644
index 0000000..338ac70
--- /dev/null
+++ b/test/fixtures/match/basic-statement/actual.js
@@ -0,0 +1,7 @@
+match x:
+  | 1:
+    "one"
+  | 2:
+    "two"
+  | else:
+    "idk"
diff --git a/test/fixtures/match/basic-statement/expected.js b/test/fixtures/match/basic-statement/expected.js
new file mode 100644
index 0000000..b4a04a2
--- /dev/null
+++ b/test/fixtures/match/basic-statement/expected.js
@@ -0,0 +1,7 @@
+if (x === 1) {
+  "one";
+} else if (x === 2) {
+  "two";
+} else {
+  "idk";
+}
diff --git a/test/fixtures/match/basic-value-checks/actual.js b/test/fixtures/match/basic-value-checks/actual.js
new file mode 100644
index 0000000..0a15e2b
--- /dev/null
+++ b/test/fixtures/match/basic-value-checks/actual.js
@@ -0,0 +1,7 @@
+match x:
+  | 1: "lt one"
+  | "hi": "eq zero"
+  | `there ${1 + 1}`: "eq two"
+  | ~f(): "f(x) truthy"
+  | .prop: "has prop"
+  | .0: "has first child"
diff --git a/test/fixtures/match/basic-value-checks/expected.js b/test/fixtures/match/basic-value-checks/expected.js
new file mode 100644
index 0000000..9cef0c8
--- /dev/null
+++ b/test/fixtures/match/basic-value-checks/expected.js
@@ -0,0 +1,13 @@
+if (x === 1) {
+    "lt one";
+  } else if (x === "hi") {
+    "eq zero";
+  } else if (x === `there ${ 1 + 1 }`) {
+    "eq two";
+  } else if (f(x)) {
+    "f(x) truthy";
+  } else if (x.prop) {
+    "has prop";
+  } else if (x[0]) {
+    "has first child";
+  }
diff --git a/test/fixtures/match/basic/actual.js b/test/fixtures/match/basic/actual.js
new file mode 100644
index 0000000..4f81cd7
--- /dev/null
+++ b/test/fixtures/match/basic/actual.js
@@ -0,0 +1,7 @@
+z = match x:
+  | 1:
+    "one"
+  | 2:
+    "two"
+  | else:
+    "idk"
diff --git a/test/fixtures/match/basic/expected.js b/test/fixtures/match/basic/expected.js
new file mode 100644
index 0000000..d1f0004
--- /dev/null
+++ b/test/fixtures/match/basic/expected.js
@@ -0,0 +1,9 @@
+const z = (_it => {
+  if (_it === 1) {
+    return "one";
+  } else if (_it === 2) {
+    return "two";
+  } else {
+    return "idk";
+  }
+})(x);
diff --git a/test/fixtures/match/no-else/actual.js b/test/fixtures/match/no-else/actual.js
new file mode 100644
index 0000000..348bdce
--- /dev/null
+++ b/test/fixtures/match/no-else/actual.js
@@ -0,0 +1,5 @@
+match x:
+  | 1:
+    "one"
+  | 2:
+    "two"
diff --git a/test/fixtures/match/no-else/expected.js b/test/fixtures/match/no-else/expected.js
new file mode 100644
index 0000000..4083116
--- /dev/null
+++ b/test/fixtures/match/no-else/expected.js
@@ -0,0 +1,5 @@
+if (x === 1) {
+  "one";
+} else if (x === 2) {
+  "two";
+}
diff --git a/test/fixtures/match/single-else-expr/actual.js b/test/fixtures/match/single-else-expr/actual.js
new file mode 100644
index 0000000..9715f57
--- /dev/null
+++ b/test/fixtures/match/single-else-expr/actual.js
@@ -0,0 +1,4 @@
+z = match x:
+  | else:
+    try {} finally {}
+    "idk"
diff --git a/test/fixtures/match/single-else-expr/expected.js b/test/fixtures/match/single-else-expr/expected.js
new file mode 100644
index 0000000..0c81fe4
--- /dev/null
+++ b/test/fixtures/match/single-else-expr/expected.js
@@ -0,0 +1,6 @@
+const z = (_it => {
+  {
+    try {} finally {}
+    return "idk";
+  }
+})(x);
diff --git a/test/fixtures/match/single-else-stmt/actual.js b/test/fixtures/match/single-else-stmt/actual.js
new file mode 100644
index 0000000..e850ffb
--- /dev/null
+++ b/test/fixtures/match/single-else-stmt/actual.js
@@ -0,0 +1,4 @@
+match x:
+  | else:
+    try {} finally {}
+    "idk"
diff --git a/test/fixtures/match/single-else-stmt/expected.js b/test/fixtures/match/single-else-stmt/expected.js
new file mode 100644
index 0000000..d1febc5
--- /dev/null
+++ b/test/fixtures/match/single-else-stmt/expected.js
@@ -0,0 +1,4 @@
+{
+  try {} finally {}
+  "idk";
+}

From a4f700cf95c1271aa9a97e68ad001e59819eebd1 Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Thu, 8 Jun 2017 15:24:53 -0700
Subject: [PATCH 2/7] wip

---
 src/index.js                                | 145 ++++++++++++++++++--
 src/stdlib.js                               |  21 +++
 test/fixtures/match/arr-pattern/actual.js   |  18 +++
 test/fixtures/match/arr-pattern/exec.js     |  92 +++++++++++++
 test/fixtures/match/arr-pattern/expected.js |  27 ++++
 test/fixtures/match/obj-pattern/actual.js   |  14 ++
 test/fixtures/match/obj-pattern/exec.js     |  36 +++++
 test/fixtures/match/obj-pattern/expected.js |  31 +++++
 8 files changed, 376 insertions(+), 8 deletions(-)
 create mode 100644 test/fixtures/match/arr-pattern/actual.js
 create mode 100644 test/fixtures/match/arr-pattern/exec.js
 create mode 100644 test/fixtures/match/arr-pattern/expected.js
 create mode 100644 test/fixtures/match/obj-pattern/actual.js
 create mode 100644 test/fixtures/match/obj-pattern/exec.js
 create mode 100644 test/fixtures/match/obj-pattern/expected.js

diff --git a/src/index.js b/src/index.js
index 5365e68..c225454 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,5 +1,5 @@
 import { parse } from "babylon-lightscript";
-import { defaultImports, lightscriptImports, lodashImports } from "./stdlib";
+import { defaultImports, lightscriptImports, lodashImports, runtimeHelpers } from "./stdlib";
 
 export default function (babel) {
   const { types: t } = babel;
@@ -580,6 +580,15 @@ export default function (babel) {
     }
   }
 
+  function collectRuntimeHelper(path, helperName) {
+    const programScope = path.scope.getProgramParent();
+    const helpers = programScope.lscRuntimeHelpers;
+    if (!helpers[helperName]) {
+      helpers[helperName] = programScope.generateUidIdentifier(helperName);
+    }
+    return helpers[helperName];
+  }
+
   function makeInlineStdlibFn(inlineFnName) {
     const fnId = t.identifier(inlineFnName);
     const aParam = t.identifier("a");
@@ -608,6 +617,16 @@ export default function (babel) {
     ]));
   }
 
+  function insertAfterImports(path, nodes) {
+    // insert inline fns before the first statement which isn't an import statement
+    for (const p of path.get("body")) {
+      if (!p.isImportDeclaration()) {
+        p.insertBefore(nodes);
+        break;
+      }
+    }
+  }
+
   function insertStdlibImports(path, imports: Imports, useRequire) {
     const declarations = [];
     const inlines = [];
@@ -653,14 +672,21 @@ export default function (babel) {
       for (const inlineFnName of inlines) {
         inlineDeclarations.push(makeInlineStdlibFn(inlineFnName));
       }
-      // insert inline fns before the first statement which isn't an import statement
-      for (const p of path.get("body")) {
-        if (!p.isImportDeclaration()) {
-          p.insertBefore(inlineDeclarations);
-          break;
-        }
-      }
+      insertAfterImports(path, inlineDeclarations);
+    }
+  }
+
+  function insertRuntimeHelpers(path) {
+    const helpers = [];
+    for (const helperName in path.scope.lscRuntimeHelpers) {
+      const fn = runtimeHelpers[helperName];
+      const uid = path.scope.lscRuntimeHelpers[helperName];
+      const fnAST = babel.template(fn.toString())({
+        [helperName]: uid,
+      });
+      helpers.push(fnAST);
     }
+    insertAfterImports(path, helpers);
   }
 
   function generateForInIterator(path, type: "array" | "object") {
@@ -827,6 +853,103 @@ export default function (babel) {
     }
   }
 
+  function extendAndChain(andChainPath, condition) {
+    if (!andChainPath.node) {
+      andChainPath.replaceWith(condition);
+    } else {
+      andChainPath.replaceWith(t.logicalExpression("&&", andChainPath.node, condition));
+    }
+  }
+
+  function buildAnd(left, right) {
+    if (left && right) {
+      return t.logicalExpression("&&", left, right);
+    } else if (left) {
+      return left;
+    } else if (right) {
+      return right;
+    } else {
+      return t.booleanLiteral(true);
+    }
+  }
+
+  function buildTestForBinding(test, bindingPath, argRef) {
+    if (bindingPath.isObjectPattern()) {
+      const isObjUid = collectRuntimeHelper(bindingPath, "hasProps");
+
+      const propsToCheck = [];
+      const childPatterns = [];  // list of [propName, path] tuples
+      for (const propPath of bindingPath.get("properties")) {
+        const propName = propPath.get("key").node.name;
+
+        if (propPath.get("value").isAssignmentPattern()) {
+          if (propPath.get("value.left").isPattern()) {
+            childPatterns.push([propName, propPath.get("value.left"), propPath.get("value.right").node]);
+          }
+        } else {
+          const propStr = t.stringLiteral(propName);
+          propsToCheck.push(propStr);
+
+          if (propPath.get("value").isPattern()) {
+            childPatterns.push([propName, propPath.get("value")]);
+          }
+        }
+      }
+
+      const isObjCall = t.callExpression(isObjUid, [argRef, t.arrayExpression(propsToCheck)]);
+      test = buildAnd(test, isObjCall);
+
+      for (const [ propName, childPatternPath, defaultObj = null ] of childPatterns) {
+        const propertyArgRef = t.memberExpression(argRef, t.identifier(propName));
+
+        if (defaultObj) {
+          test = buildAnd(test, t.logicalExpression("||",
+            buildTestForBinding(null, childPatternPath, propertyArgRef),
+            buildTestForBinding(null, childPatternPath, defaultObj)
+          ));
+        } else {
+          test = buildTestForBinding(test, childPatternPath, propertyArgRef);
+        }
+      }
+    } else if (bindingPath.isArrayPattern()) {
+      const hasLengthUid = collectRuntimeHelper(bindingPath, "hasLength");
+
+      const childPatterns = []; // list of [index, path] tuples.
+      let minLength = 0;
+      let maxLength = 0;
+      bindingPath.get("elements").forEach((elemPath, i) => {
+        if (elemPath.isAssignmentPattern()) {
+          ++maxLength;
+          if (elemPath.get("left").isPattern()) {
+            childPatterns.push([i, elemPath.get("left")]);
+          }
+        } else if (elemPath.isRestElement()) {
+          maxLength = null;
+        } else {
+          ++minLength;
+          ++maxLength;
+          if (elemPath.isPattern()) {
+            childPatterns.push([i, elemPath]);
+          }
+        }
+      });
+
+      const hasLengthCall = t.callExpression(hasLengthUid, [
+        argRef,
+        t.numericLiteral(minLength),
+        maxLength === null ? null : t.numericLiteral(maxLength)
+      ].filter(x => x !== null));
+      test = buildAnd(test, hasLengthCall);
+
+      for (const [index, childPatternPath] of childPatterns) {
+        const elementArgRef = t.memberExpression(argRef, t.numericLiteral(index), true);
+        test = buildTestForBinding(test, childPatternPath, elementArgRef);
+      }
+    } else throw new TypeError(`Expected Pattern, got ${bindingPath.node.type}`);
+
+    return test;
+  }
+
   function transformMatchCases(argRef, cases) {
     return cases.reduce((rootIf, path) => {
 
@@ -843,6 +966,10 @@ export default function (babel) {
       // add binding (and always use block bodies)
       ensureBlockBody(path, "consequent");
       if (path.node.binding) {
+        const bindingTest = buildTestForBinding(null, path.get("binding"), argRef);
+        const testWithBindingTest = buildAnd(path.get("test").node, bindingTest)
+        path.get("test").replaceWith(testWithBindingTest);
+
         const bindingDecl = t.variableDeclaration("const", [
           t.variableDeclarator(path.node.binding, argRef)
         ]);
@@ -1128,6 +1255,7 @@ export default function (babel) {
     const stdlib: Stdlib = initializeStdlib(state.opts);
     const useRequire = state.opts.stdlib && state.opts.stdlib.require === true;
     const imports: Imports = {};
+    path.scope.lscRuntimeHelpers = {};
 
     path.traverse({
 
@@ -1451,6 +1579,7 @@ export default function (babel) {
     });
 
     insertStdlibImports(path, imports, useRequire);
+    insertRuntimeHelpers(path);
   }
 
   return {
diff --git a/src/stdlib.js b/src/stdlib.js
index 42197c2..434342e 100644
--- a/src/stdlib.js
+++ b/src/stdlib.js
@@ -11,6 +11,27 @@ export const lightscriptImports = {
   "bitwiseZeroFillRightShift": "inline",
 };
 
+export const runtimeHelpers = {
+  hasProps: function hasProps(obj, props) {
+    return (
+      obj != null &&
+      (typeof obj === "object" || typeof obj === "function") &&
+      props.filter(prop => prop in obj).length === props.length
+    );
+  },
+  hasLength: function hasLength(arr, minLength, maxLength) {
+    minLength = minLength || 0;
+    maxLength = maxLength != null ? maxLength : Number.MAX_SAFE_INTEGER;
+    return (
+      arr != null &&
+      typeof arr !== "function" &&
+      arr.length === arr.length|0 &&
+      arr.length >= minLength &&
+      arr.length <= maxLength
+    );
+  },
+};
+
 export const everyLodashMethod = [
   "add",
   "after",
diff --git a/test/fixtures/match/arr-pattern/actual.js b/test/fixtures/match/arr-pattern/actual.js
new file mode 100644
index 0000000..8a4c92d
--- /dev/null
+++ b/test/fixtures/match/arr-pattern/actual.js
@@ -0,0 +1,18 @@
+match x:
+  | []:
+    "empty"
+  | [ a, b ]:
+    a - b
+  | [ a, b = 2 ]:
+    a + b - 2
+  | [ a, ...b ]:
+    b.concat(a)
+  | [
+      [
+        b
+        d = 'e'
+      ]
+      [ g, , h ]
+      ...j
+  ]:
+    [b, d, g, ...j].join('')
diff --git a/test/fixtures/match/arr-pattern/exec.js b/test/fixtures/match/arr-pattern/exec.js
new file mode 100644
index 0000000..db39428
--- /dev/null
+++ b/test/fixtures/match/arr-pattern/exec.js
@@ -0,0 +1,92 @@
+assert.equal(
+  "empty",
+  match []:
+    | []:
+      "empty"
+)
+assert.equal(
+  "empty",
+  match []:
+    | []:
+      "empty"
+)
+assert.equal(
+  undefined,
+  match []:
+    | [a]:
+      a + 1
+)
+assert.equal(
+  undefined,
+  match [1]:
+    | [a, b]:
+      a + b
+)
+assert.equal(
+  5,
+  match [1]:
+    | [a, b = 4]:
+      a + b
+)
+assert.equal(
+  3,
+  match [1, 2]:
+    | [a, b]:
+      a + b
+)
+assert.equal(
+  4,
+  match [1, 2, 3]:
+    | [a,, b]:
+      a + b
+)
+assert.equal(
+  undefined,
+  match [1, 2]:
+    | [a,, b]:
+      a + b
+)
+assert.deepEqual(
+  [2, 3, 1],
+  match [1, 2, 3]:
+    | [a, ...b]:
+      b.concat(a)
+)
+assert.deepEqual(
+  [1, 4],
+  match [4]:
+    | [a, b = 1, ...c]:
+      c.concat([b, a])
+)
+assert.deepEqual(
+  [6, 7, 5, 4],
+  match [4, 5, 6, 7]:
+    | [a, b = 1, ...c]:
+      c.concat([b, a])
+)
+assert.deepEqual(
+  [1, 2, 4, 6, 7, 8],
+  match [[1], [4, 5, 6], 7, 8]:
+    | [
+        [
+          b
+          d = 2
+        ]
+        [ g, , h ]
+        ...j
+    ]:
+      [b, d, g, h, ...j]
+)
+assert.deepEqual(
+  undefined,
+  match [[1], [4, 5], 7, 8]:
+    | [
+        [
+          b
+          d = 2
+        ]
+        [ g, , h ]
+        ...j
+    ]:
+      [b, d, g, h, ...j]
+)
diff --git a/test/fixtures/match/arr-pattern/expected.js b/test/fixtures/match/arr-pattern/expected.js
new file mode 100644
index 0000000..97e2a6c
--- /dev/null
+++ b/test/fixtures/match/arr-pattern/expected.js
@@ -0,0 +1,27 @@
+function _hasLength(arr, minLength, maxLength) {
+  minLength = minLength || 0;
+  maxLength = maxLength != null ? maxLength : Number.MAX_SAFE_INTEGER;
+  return arr != null && typeof arr !== "function" && arr.length === arr.length | 0 && arr.length >= minLength && arr.length <= maxLength;
+}
+
+if (_hasLength(x, 0, 0)) {
+  const [] = x;
+
+  "empty";
+} else if (_hasLength(x, 2, 2)) {
+  const [a, b] = x;
+
+  a - b;
+} else if (_hasLength(x, 1, 2)) {
+  const [a, b = 2] = x;
+
+  a + b - 2;
+} else if (_hasLength(x, 1)) {
+  const [a, ...b] = x;
+
+  b.concat(a);
+} else if (_hasLength(x, 2) && _hasLength(x[0], 1, 2) && _hasLength(x[1], 3, 3)) {
+  const [[b, d = 'e'], [g,, h], ...j] = x;
+
+  [b, d, g, ...j].join('');
+}
diff --git a/test/fixtures/match/obj-pattern/actual.js b/test/fixtures/match/obj-pattern/actual.js
new file mode 100644
index 0000000..5ca3636
--- /dev/null
+++ b/test/fixtures/match/obj-pattern/actual.js
@@ -0,0 +1,14 @@
+match x:
+  | { a }:
+    a
+  | { a, b }:
+    a + b
+  | { a, b = 1 }:
+    a + b
+  | { a, b: { ba, bb = 1 }, c: { ca, cb: { cba } } }:
+    a + ba + bb + ca + cba
+  | 1 or 2 with { a, b: { c } }:
+    a + c
+  | { a: { b: { c } } = otherObj }:
+    c
+  //TODO: | { a, ...b }: b
diff --git a/test/fixtures/match/obj-pattern/exec.js b/test/fixtures/match/obj-pattern/exec.js
new file mode 100644
index 0000000..65fbdb6
--- /dev/null
+++ b/test/fixtures/match/obj-pattern/exec.js
@@ -0,0 +1,36 @@
+assert.equal(
+  1,
+  match { a: 1 }:
+    | { a }:
+      a
+)
+assert.equal(
+  undefined,
+  match { b: 1 }:
+    | { a }:
+      a
+)
+assert.equal(
+  3,
+  match { a: 1 }:
+    | { a, b = 2 }:
+      a + b
+)
+assert.equal(
+  undefined,
+  match { b: 1 }:
+    | { a, b = 2 }:
+      a + b
+)
+assert.equal(
+  3,
+  match { a: 1, b: { c: 2 } }:
+    | { a, b: { c } }:
+      a + c
+)
+assert.equal(
+  undefined,
+  match { a: 1 }:
+    | { a, b: { c } }:
+      a + c
+)
diff --git a/test/fixtures/match/obj-pattern/expected.js b/test/fixtures/match/obj-pattern/expected.js
new file mode 100644
index 0000000..2302b8c
--- /dev/null
+++ b/test/fixtures/match/obj-pattern/expected.js
@@ -0,0 +1,31 @@
+function _hasProps(obj, props) {
+  return obj != null && (typeof obj === "object" || typeof obj === "function") && props.filter(function (prop) {
+    return prop in obj;
+  }).length === props.length;
+}
+
+if (_hasProps(x, ["a"])) {
+  const { a } = x;
+
+  a;
+} else if (_hasProps(x, ["a", "b"])) {
+  const { a, b } = x;
+
+  a + b;
+} else if (_hasProps(x, ["a"])) {
+  const { a, b = 1 } = x;
+
+  a + b;
+} else if (_hasProps(x, ["a", "b", "c"]) && _hasProps(x.b, ["ba"]) && _hasProps(x.c, ["ca", "cb"]) && _hasProps(x.c.cb, ["cba"])) {
+  const { a, b: { ba, bb = 1 }, c: { ca, cb: { cba } } } = x;
+
+  a + ba + bb + ca + cba;
+} else if ((x === 1 || x === 2) && _hasProps(x, ["a", "b"]) && _hasProps(x.b, ["c"])) {
+  const { a, b: { c } } = x;
+
+  a + c;
+} else if (_hasProps(x, []) && (_hasProps(x.a, ["b"]) && _hasProps(x.a.b, ["c"]) || _hasProps(otherObj, ["b"]) && _hasProps(otherObj.b, ["c"]))) {
+  const { a: { b: { c } } = otherObj } = x;
+
+  c;
+} //TODO: | { a, ...b }: b

From 4c3d2df95adec550f6c449348a86aa9d846eaa47 Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Thu, 8 Jun 2017 22:15:04 -0700
Subject: [PATCH 3/7] wip more tests

---
 .../match/basic-value-checks/actual.js        | 24 ++++++++++----
 .../match/basic-value-checks/expected.js      | 32 +++++++++++--------
 test/fixtures/match/not/actual.js             |  5 +++
 test/fixtures/match/not/expected.js           |  5 +++
 4 files changed, 47 insertions(+), 19 deletions(-)
 create mode 100644 test/fixtures/match/not/actual.js
 create mode 100644 test/fixtures/match/not/expected.js

diff --git a/test/fixtures/match/basic-value-checks/actual.js b/test/fixtures/match/basic-value-checks/actual.js
index 0a15e2b..8a68ae6 100644
--- a/test/fixtures/match/basic-value-checks/actual.js
+++ b/test/fixtures/match/basic-value-checks/actual.js
@@ -1,7 +1,19 @@
 match x:
-  | 1: "lt one"
-  | "hi": "eq zero"
-  | `there ${1 + 1}`: "eq two"
-  | ~f(): "f(x) truthy"
-  | .prop: "has prop"
-  | .0: "has first child"
+  | 1 or 0.1 or 0x11 or +1 or -1:
+    it
+  | "hi":
+    it
+  | `there ${1 + 1}`:
+    it
+  | /\s+/:
+    it
+  | Number or Boolean or String:
+    it
+  | Array or Object or Map or Foo:
+    it
+  | null or undefined:
+    it
+  | x or +x:
+    it
+  | not 1 or not x:
+    it
diff --git a/test/fixtures/match/basic-value-checks/expected.js b/test/fixtures/match/basic-value-checks/expected.js
index 9cef0c8..6dec644 100644
--- a/test/fixtures/match/basic-value-checks/expected.js
+++ b/test/fixtures/match/basic-value-checks/expected.js
@@ -1,13 +1,19 @@
-if (x === 1) {
-    "lt one";
-  } else if (x === "hi") {
-    "eq zero";
-  } else if (x === `there ${ 1 + 1 }`) {
-    "eq two";
-  } else if (f(x)) {
-    "f(x) truthy";
-  } else if (x.prop) {
-    "has prop";
-  } else if (x[0]) {
-    "has first child";
-  }
+if (x === 1 || x === 0.1 || x === 0x11 || x === +1 || x === -1) {
+  it;
+} else if (x === "hi") {
+  it;
+} else if (x === `there ${ 1 + 1 }`) {
+  it;
+} else if (/\s+/.test(x)) {
+  it;
+} else if (typeof x === "number" || typeof x === "boolean" || typeof x === "string") {
+  it;
+} else if (x instanceof Array || x instanceof Object || x instanceof Map || x instanceof Foo) {
+  it;
+} else if (x === null || x === undefined) {
+  it;
+} else if (x || +x) {
+  it;
+} else if (!(x === 1) || !x) {
+  it;
+}
diff --git a/test/fixtures/match/not/actual.js b/test/fixtures/match/not/actual.js
new file mode 100644
index 0000000..6148821
--- /dev/null
+++ b/test/fixtures/match/not/actual.js
@@ -0,0 +1,5 @@
+match x:
+  | not 1 or not Number or not "hi":
+    it
+  | not x or not 1 + 1 or not foo(bar):
+    it
diff --git a/test/fixtures/match/not/expected.js b/test/fixtures/match/not/expected.js
new file mode 100644
index 0000000..8cb3a7c
--- /dev/null
+++ b/test/fixtures/match/not/expected.js
@@ -0,0 +1,5 @@
+if (!(x === 1) || !(typeof x === "number") || !(x === "hi")) {
+  it;
+} else if (!x || !1 + 1 || !foo(bar)) {
+  it;
+}
\ No newline at end of file

From 53951930236b6248da388f5ca95af51d93a78e37 Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Fri, 9 Jun 2017 12:46:33 -0700
Subject: [PATCH 4/7] Replace PlaceholderExpression with it

---
 src/index.js                                  | 32 +++++++++++--------
 test/fixtures/match/arr-pattern/actual.js     | 10 +++---
 test/fixtures/match/arr-pattern/exec.js       | 26 +++++++--------
 .../match/as-call-expression/actual.js        |  7 ++++
 .../match/as-call-expression/expected.js      | 15 +++++++++
 .../match/as-call-statement/actual.js         |  7 ++++
 .../match/as-call-statement/expected.js       | 15 +++++++++
 .../match/as-identifier-expression/actual.js  |  7 ++++
 .../as-identifier-expression/expected.js      | 15 +++++++++
 .../actual.js                                 |  3 ++
 .../expected.js                               |  7 ++++
 .../actual.js                                 |  3 ++
 .../expected.js                               |  5 +++
 .../match/as-identifier-statement/actual.js   |  7 ++++
 .../match/as-identifier-statement/expected.js | 15 +++++++++
 .../match/as-it-call-expression/actual.js     |  7 ++++
 .../match/as-it-call-expression/expected.js   | 15 +++++++++
 .../match/as-it-call-statement/actual.js      |  7 ++++
 .../match/as-it-call-statement/expected.js    | 15 +++++++++
 .../as-it-identifier-expression/actual.js     |  7 ++++
 .../as-it-identifier-expression/expected.js   | 15 +++++++++
 .../as-it-identifier-statement/actual.js      |  7 ++++
 .../as-it-identifier-statement/expected.js    | 15 +++++++++
 .../match/basic-placeholder/actual.js         |  7 ----
 .../match/basic-placeholder/expected.js       | 13 --------
 .../match/basic-statement-call/actual.js      |  7 ++++
 .../match/basic-statement-call/expected.js    |  9 ++++++
 .../match/basic-value-checks/expected.js      | 20 ++++++------
 test/fixtures/match/basic/expected.js         |  6 ++--
 test/fixtures/match/not/actual.js             |  2 +-
 test/fixtures/match/not/expected.js           |  6 ++--
 test/fixtures/match/obj-pattern/actual.js     | 12 +++----
 test/fixtures/match/obj-pattern/exec.js       | 12 +++----
 test/fixtures/match/obj-pattern/expected.js   |  2 +-
 .../match/single-else-expr/expected.js        |  2 +-
 35 files changed, 279 insertions(+), 81 deletions(-)
 create mode 100644 test/fixtures/match/as-call-expression/actual.js
 create mode 100644 test/fixtures/match/as-call-expression/expected.js
 create mode 100644 test/fixtures/match/as-call-statement/actual.js
 create mode 100644 test/fixtures/match/as-call-statement/expected.js
 create mode 100644 test/fixtures/match/as-identifier-expression/actual.js
 create mode 100644 test/fixtures/match/as-identifier-expression/expected.js
 create mode 100644 test/fixtures/match/as-identifier-statement-body-reference/actual.js
 create mode 100644 test/fixtures/match/as-identifier-statement-body-reference/expected.js
 create mode 100644 test/fixtures/match/as-identifier-statement-not-referenced/actual.js
 create mode 100644 test/fixtures/match/as-identifier-statement-not-referenced/expected.js
 create mode 100644 test/fixtures/match/as-identifier-statement/actual.js
 create mode 100644 test/fixtures/match/as-identifier-statement/expected.js
 create mode 100644 test/fixtures/match/as-it-call-expression/actual.js
 create mode 100644 test/fixtures/match/as-it-call-expression/expected.js
 create mode 100644 test/fixtures/match/as-it-call-statement/actual.js
 create mode 100644 test/fixtures/match/as-it-call-statement/expected.js
 create mode 100644 test/fixtures/match/as-it-identifier-expression/actual.js
 create mode 100644 test/fixtures/match/as-it-identifier-expression/expected.js
 create mode 100644 test/fixtures/match/as-it-identifier-statement/actual.js
 create mode 100644 test/fixtures/match/as-it-identifier-statement/expected.js
 delete mode 100644 test/fixtures/match/basic-placeholder/actual.js
 delete mode 100644 test/fixtures/match/basic-placeholder/expected.js
 create mode 100644 test/fixtures/match/basic-statement-call/actual.js
 create mode 100644 test/fixtures/match/basic-statement-call/expected.js

diff --git a/src/index.js b/src/index.js
index c225454..dffb331 100644
--- a/src/index.js
+++ b/src/index.js
@@ -950,16 +950,22 @@ export default function (babel) {
     return test;
   }
 
+  function containsAliasReference(path, alias) {
+    let containsAlias = false;
+    path.traverse({
+      ReferencedIdentifier(refPath) {
+        if (refPath.node.name === alias.name) {
+          containsAlias = true;
+          refPath.stop();
+        }
+      }
+    });
+    return containsAlias;
+  }
+
   function transformMatchCases(argRef, cases) {
     return cases.reduce((rootIf, path) => {
 
-      // fill in placeholders
-      path.get("test").traverse({
-        PlaceholderExpression(placeholderPath) {
-          placeholderPath.replaceWith(argRef);
-        }
-      });
-
       // add in ===, etc
       transformMatchCaseTest(path.get("test"), argRef);
 
@@ -1243,9 +1249,6 @@ export default function (babel) {
     // only allowed in MatchCase, so don't alias to Expression
   });
 
-  definePluginType("PlaceholderExpression", {
-    aliases: ["Expression"]
-  });
 
   // traverse as top-level item so as to run before other babel plugins
   // (and avoid traversing any of their output)
@@ -1547,9 +1550,9 @@ export default function (babel) {
       },
 
       MatchExpression(path) {
-        const { discriminant } = path.node;
+        const { discriminant, alias = null } = path.node;
 
-        const argRef = path.scope.generateUidIdentifier("it");
+        const argRef = alias || t.identifier("it");
         const matchBody = transformMatchCases(argRef, path.get("cases"));
 
         const iife = t.callExpression(
@@ -1561,12 +1564,13 @@ export default function (babel) {
 
       MatchStatement(path) {
         const { discriminant } = path.node;
+        const alias = path.node.alias || t.identifier("it");
 
         let argRef;
-        if (t.isIdentifier(discriminant)) {
+        if (t.isIdentifier(discriminant) && !containsAliasReference(path, alias)) {
           argRef = discriminant;
         } else {
-          argRef = path.scope.generateUidIdentifier("it");
+          argRef = alias;
           path.insertBefore(t.variableDeclaration("const", [
             t.variableDeclarator(argRef, discriminant)
           ]));
diff --git a/test/fixtures/match/arr-pattern/actual.js b/test/fixtures/match/arr-pattern/actual.js
index 8a4c92d..86e8508 100644
--- a/test/fixtures/match/arr-pattern/actual.js
+++ b/test/fixtures/match/arr-pattern/actual.js
@@ -1,13 +1,13 @@
 match x:
-  | []:
+  | with []:
     "empty"
-  | [ a, b ]:
+  | with [ a, b ]:
     a - b
-  | [ a, b = 2 ]:
+  | with [ a, b = 2 ]:
     a + b - 2
-  | [ a, ...b ]:
+  | with [ a, ...b ]:
     b.concat(a)
-  | [
+  | with [
       [
         b
         d = 'e'
diff --git a/test/fixtures/match/arr-pattern/exec.js b/test/fixtures/match/arr-pattern/exec.js
index db39428..685bb45 100644
--- a/test/fixtures/match/arr-pattern/exec.js
+++ b/test/fixtures/match/arr-pattern/exec.js
@@ -1,73 +1,73 @@
 assert.equal(
   "empty",
   match []:
-    | []:
+    | with []:
       "empty"
 )
 assert.equal(
   "empty",
   match []:
-    | []:
+    | with []:
       "empty"
 )
 assert.equal(
   undefined,
   match []:
-    | [a]:
+    | with [a]:
       a + 1
 )
 assert.equal(
   undefined,
   match [1]:
-    | [a, b]:
+    | with [a, b]:
       a + b
 )
 assert.equal(
   5,
   match [1]:
-    | [a, b = 4]:
+    | with [a, b = 4]:
       a + b
 )
 assert.equal(
   3,
   match [1, 2]:
-    | [a, b]:
+    | with [a, b]:
       a + b
 )
 assert.equal(
   4,
   match [1, 2, 3]:
-    | [a,, b]:
+    | with [a,, b]:
       a + b
 )
 assert.equal(
   undefined,
   match [1, 2]:
-    | [a,, b]:
+    | with [a,, b]:
       a + b
 )
 assert.deepEqual(
   [2, 3, 1],
   match [1, 2, 3]:
-    | [a, ...b]:
+    | with [a, ...b]:
       b.concat(a)
 )
 assert.deepEqual(
   [1, 4],
   match [4]:
-    | [a, b = 1, ...c]:
+    | with [a, b = 1, ...c]:
       c.concat([b, a])
 )
 assert.deepEqual(
   [6, 7, 5, 4],
   match [4, 5, 6, 7]:
-    | [a, b = 1, ...c]:
+    | with [a, b = 1, ...c]:
       c.concat([b, a])
 )
 assert.deepEqual(
   [1, 2, 4, 6, 7, 8],
   match [[1], [4, 5, 6], 7, 8]:
-    | [
+    | with [
         [
           b
           d = 2
@@ -80,7 +80,7 @@ assert.deepEqual(
 assert.deepEqual(
   undefined,
   match [[1], [4, 5], 7, 8]:
-    | [
+    | with [
         [
           b
           d = 2
diff --git a/test/fixtures/match/as-call-expression/actual.js b/test/fixtures/match/as-call-expression/actual.js
new file mode 100644
index 0000000..3022db5
--- /dev/null
+++ b/test/fixtures/match/as-call-expression/actual.js
@@ -0,0 +1,7 @@
+z = match foo.bar() as y:
+  | y < 1: "lt one"
+  | y + 1 == 1: "eq zero"
+  | y == 2: "eq two"
+  | y~f(): "f(x) truthy"
+  | y.prop: "has prop"
+  | y.0: "has first child"
diff --git a/test/fixtures/match/as-call-expression/expected.js b/test/fixtures/match/as-call-expression/expected.js
new file mode 100644
index 0000000..9c3eb0f
--- /dev/null
+++ b/test/fixtures/match/as-call-expression/expected.js
@@ -0,0 +1,15 @@
+const z = (y => {
+  if (y < 1) {
+      return "lt one";
+    } else if (y + 1 === 1) {
+      return "eq zero";
+    } else if (y === 2) {
+      return "eq two";
+    } else if (f(y)) {
+      return "f(x) truthy";
+    } else if (y.prop) {
+      return "has prop";
+    } else if (y[0]) {
+      return "has first child";
+    }
+})(foo.bar());
diff --git a/test/fixtures/match/as-call-statement/actual.js b/test/fixtures/match/as-call-statement/actual.js
new file mode 100644
index 0000000..fa39259
--- /dev/null
+++ b/test/fixtures/match/as-call-statement/actual.js
@@ -0,0 +1,7 @@
+match foo() as y:
+  | y < 1: "lt one"
+  | y + 1 == 1: "eq zero"
+  | y == 2: "eq two"
+  | y~f(): "f(y) truthy"
+  | y.prop: "has prop"
+  | y.0: "has first child"
diff --git a/test/fixtures/match/as-call-statement/expected.js b/test/fixtures/match/as-call-statement/expected.js
new file mode 100644
index 0000000..2495206
--- /dev/null
+++ b/test/fixtures/match/as-call-statement/expected.js
@@ -0,0 +1,15 @@
+const y = foo();
+
+if (y < 1) {
+    "lt one";
+  } else if (y + 1 === 1) {
+    "eq zero";
+  } else if (y === 2) {
+    "eq two";
+  } else if (f(y)) {
+    "f(y) truthy";
+  } else if (y.prop) {
+    "has prop";
+  } else if (y[0]) {
+    "has first child";
+  }
diff --git a/test/fixtures/match/as-identifier-expression/actual.js b/test/fixtures/match/as-identifier-expression/actual.js
new file mode 100644
index 0000000..b0a69e6
--- /dev/null
+++ b/test/fixtures/match/as-identifier-expression/actual.js
@@ -0,0 +1,7 @@
+z = match x as y:
+  | y < 1: "lt one"
+  | y + 1 == 1: "eq zero"
+  | y == 2: "eq two"
+  | y~f(): "f(x) truthy"
+  | y.prop: "has prop"
+  | y.0: "has first child"
diff --git a/test/fixtures/match/as-identifier-expression/expected.js b/test/fixtures/match/as-identifier-expression/expected.js
new file mode 100644
index 0000000..7ad5dd7
--- /dev/null
+++ b/test/fixtures/match/as-identifier-expression/expected.js
@@ -0,0 +1,15 @@
+const z = (y => {
+  if (y < 1) {
+      return "lt one";
+    } else if (y + 1 === 1) {
+      return "eq zero";
+    } else if (y === 2) {
+      return "eq two";
+    } else if (f(y)) {
+      return "f(x) truthy";
+    } else if (y.prop) {
+      return "has prop";
+    } else if (y[0]) {
+      return "has first child";
+    }
+})(x);
diff --git a/test/fixtures/match/as-identifier-statement-body-reference/actual.js b/test/fixtures/match/as-identifier-statement-body-reference/actual.js
new file mode 100644
index 0000000..51b13d9
--- /dev/null
+++ b/test/fixtures/match/as-identifier-statement-body-reference/actual.js
@@ -0,0 +1,3 @@
+match x:
+  | 1: "foo"
+  | "1": it
diff --git a/test/fixtures/match/as-identifier-statement-body-reference/expected.js b/test/fixtures/match/as-identifier-statement-body-reference/expected.js
new file mode 100644
index 0000000..0d3448c
--- /dev/null
+++ b/test/fixtures/match/as-identifier-statement-body-reference/expected.js
@@ -0,0 +1,7 @@
+const it = x;
+
+if (it === 1) {
+    "foo";
+  } else if (it === "1") {
+    it;
+  }
diff --git a/test/fixtures/match/as-identifier-statement-not-referenced/actual.js b/test/fixtures/match/as-identifier-statement-not-referenced/actual.js
new file mode 100644
index 0000000..de807c5
--- /dev/null
+++ b/test/fixtures/match/as-identifier-statement-not-referenced/actual.js
@@ -0,0 +1,3 @@
+match x:
+  | 1: "foo"
+  | "1": "bar"
diff --git a/test/fixtures/match/as-identifier-statement-not-referenced/expected.js b/test/fixtures/match/as-identifier-statement-not-referenced/expected.js
new file mode 100644
index 0000000..eb590d2
--- /dev/null
+++ b/test/fixtures/match/as-identifier-statement-not-referenced/expected.js
@@ -0,0 +1,5 @@
+if (x === 1) {
+    "foo";
+  } else if (x === "1") {
+    "bar";
+  }
diff --git a/test/fixtures/match/as-identifier-statement/actual.js b/test/fixtures/match/as-identifier-statement/actual.js
new file mode 100644
index 0000000..c9c7d02
--- /dev/null
+++ b/test/fixtures/match/as-identifier-statement/actual.js
@@ -0,0 +1,7 @@
+match x as y:
+  | y < 1: "lt one"
+  | y + 1 == 1: "eq zero"
+  | y == 2: "eq two"
+  | y~f(): "f(x) truthy"
+  | y.prop: "has prop"
+  | y.0: "has first child"
diff --git a/test/fixtures/match/as-identifier-statement/expected.js b/test/fixtures/match/as-identifier-statement/expected.js
new file mode 100644
index 0000000..ab33968
--- /dev/null
+++ b/test/fixtures/match/as-identifier-statement/expected.js
@@ -0,0 +1,15 @@
+const y = x;
+
+if (y < 1) {
+    "lt one";
+  } else if (y + 1 === 1) {
+    "eq zero";
+  } else if (y === 2) {
+    "eq two";
+  } else if (f(y)) {
+    "f(x) truthy";
+  } else if (y.prop) {
+    "has prop";
+  } else if (y[0]) {
+    "has first child";
+  }
diff --git a/test/fixtures/match/as-it-call-expression/actual.js b/test/fixtures/match/as-it-call-expression/actual.js
new file mode 100644
index 0000000..6b68dac
--- /dev/null
+++ b/test/fixtures/match/as-it-call-expression/actual.js
@@ -0,0 +1,7 @@
+z = match foo.bar():
+  | it < 1: "lt one"
+  | it + 1 == 1: "eq zero"
+  | it == 2: "eq two"
+  | it~f(): "f(x) truthy"
+  | it.prop: "has prop"
+  | it.0: "has first child"
diff --git a/test/fixtures/match/as-it-call-expression/expected.js b/test/fixtures/match/as-it-call-expression/expected.js
new file mode 100644
index 0000000..0b417c8
--- /dev/null
+++ b/test/fixtures/match/as-it-call-expression/expected.js
@@ -0,0 +1,15 @@
+const z = (it => {
+  if (it < 1) {
+      return "lt one";
+    } else if (it + 1 === 1) {
+      return "eq zero";
+    } else if (it === 2) {
+      return "eq two";
+    } else if (f(it)) {
+      return "f(x) truthy";
+    } else if (it.prop) {
+      return "has prop";
+    } else if (it[0]) {
+      return "has first child";
+    }
+})(foo.bar());
diff --git a/test/fixtures/match/as-it-call-statement/actual.js b/test/fixtures/match/as-it-call-statement/actual.js
new file mode 100644
index 0000000..0097bbb
--- /dev/null
+++ b/test/fixtures/match/as-it-call-statement/actual.js
@@ -0,0 +1,7 @@
+match foo():
+  | it < 1: "lt one"
+  | it + 1 == 1: "eq zero"
+  | it == 2: "eq two"
+  | it~f(): "f(x) truthy"
+  | it.prop: "has prop"
+  | it.0: "has first child"
diff --git a/test/fixtures/match/as-it-call-statement/expected.js b/test/fixtures/match/as-it-call-statement/expected.js
new file mode 100644
index 0000000..9215777
--- /dev/null
+++ b/test/fixtures/match/as-it-call-statement/expected.js
@@ -0,0 +1,15 @@
+const it = foo();
+
+if (it < 1) {
+    "lt one";
+  } else if (it + 1 === 1) {
+    "eq zero";
+  } else if (it === 2) {
+    "eq two";
+  } else if (f(it)) {
+    "f(x) truthy";
+  } else if (it.prop) {
+    "has prop";
+  } else if (it[0]) {
+    "has first child";
+  }
diff --git a/test/fixtures/match/as-it-identifier-expression/actual.js b/test/fixtures/match/as-it-identifier-expression/actual.js
new file mode 100644
index 0000000..c7779e8
--- /dev/null
+++ b/test/fixtures/match/as-it-identifier-expression/actual.js
@@ -0,0 +1,7 @@
+z = match x:
+  | it < 1: "lt one"
+  | it + 1 == 1: "eq zero"
+  | it == 2: "eq two"
+  | it~f(): "f(x) truthy"
+  | it.prop: "has prop"
+  | it.0: "has first child"
diff --git a/test/fixtures/match/as-it-identifier-expression/expected.js b/test/fixtures/match/as-it-identifier-expression/expected.js
new file mode 100644
index 0000000..2382825
--- /dev/null
+++ b/test/fixtures/match/as-it-identifier-expression/expected.js
@@ -0,0 +1,15 @@
+const z = (it => {
+  if (it < 1) {
+      return "lt one";
+    } else if (it + 1 === 1) {
+      return "eq zero";
+    } else if (it === 2) {
+      return "eq two";
+    } else if (f(it)) {
+      return "f(x) truthy";
+    } else if (it.prop) {
+      return "has prop";
+    } else if (it[0]) {
+      return "has first child";
+    }
+})(x);
diff --git a/test/fixtures/match/as-it-identifier-statement/actual.js b/test/fixtures/match/as-it-identifier-statement/actual.js
new file mode 100644
index 0000000..b778a3f
--- /dev/null
+++ b/test/fixtures/match/as-it-identifier-statement/actual.js
@@ -0,0 +1,7 @@
+match x:
+  | it < 1: "lt one"
+  | it + 1 == 1: "eq zero"
+  | it == 2: "eq two"
+  | it~f(): "f(x) truthy"
+  | it.prop: "has prop"
+  | it.0: "has first child"
diff --git a/test/fixtures/match/as-it-identifier-statement/expected.js b/test/fixtures/match/as-it-identifier-statement/expected.js
new file mode 100644
index 0000000..2187c8c
--- /dev/null
+++ b/test/fixtures/match/as-it-identifier-statement/expected.js
@@ -0,0 +1,15 @@
+const it = x;
+
+if (it < 1) {
+    "lt one";
+  } else if (it + 1 === 1) {
+    "eq zero";
+  } else if (it === 2) {
+    "eq two";
+  } else if (f(it)) {
+    "f(x) truthy";
+  } else if (it.prop) {
+    "has prop";
+  } else if (it[0]) {
+    "has first child";
+  }
diff --git a/test/fixtures/match/basic-placeholder/actual.js b/test/fixtures/match/basic-placeholder/actual.js
deleted file mode 100644
index 61c0908..0000000
--- a/test/fixtures/match/basic-placeholder/actual.js
+++ /dev/null
@@ -1,7 +0,0 @@
-match x:
-  | < 1: "lt one"
-  | + 1 == 1: "eq zero"
-  | == 2: "eq two"
-  | ~f(): "f(x) truthy"
-  | .prop: "has prop"
-  | .0: "has first child"
diff --git a/test/fixtures/match/basic-placeholder/expected.js b/test/fixtures/match/basic-placeholder/expected.js
deleted file mode 100644
index d0d1511..0000000
--- a/test/fixtures/match/basic-placeholder/expected.js
+++ /dev/null
@@ -1,13 +0,0 @@
-if (x < 1) {
-    "lt one";
-  } else if (x + 1 === 1) {
-    "eq zero";
-  } else if (x === 2) {
-    "eq two";
-  } else if (f(x)) {
-    "f(x) truthy";
-  } else if (x.prop) {
-    "has prop";
-  } else if (x[0]) {
-    "has first child";
-  }
diff --git a/test/fixtures/match/basic-statement-call/actual.js b/test/fixtures/match/basic-statement-call/actual.js
new file mode 100644
index 0000000..5de670d
--- /dev/null
+++ b/test/fixtures/match/basic-statement-call/actual.js
@@ -0,0 +1,7 @@
+match foo():
+  | 1:
+    "one"
+  | 2:
+    "two"
+  | else:
+    "idk"
diff --git a/test/fixtures/match/basic-statement-call/expected.js b/test/fixtures/match/basic-statement-call/expected.js
new file mode 100644
index 0000000..de54b42
--- /dev/null
+++ b/test/fixtures/match/basic-statement-call/expected.js
@@ -0,0 +1,9 @@
+const it = foo();
+
+if (it === 1) {
+  "one";
+} else if (it === 2) {
+  "two";
+} else {
+  "idk";
+}
diff --git a/test/fixtures/match/basic-value-checks/expected.js b/test/fixtures/match/basic-value-checks/expected.js
index 6dec644..4dae010 100644
--- a/test/fixtures/match/basic-value-checks/expected.js
+++ b/test/fixtures/match/basic-value-checks/expected.js
@@ -1,19 +1,21 @@
-if (x === 1 || x === 0.1 || x === 0x11 || x === +1 || x === -1) {
+const it = x;
+
+if (it === 1 || it === 0.1 || it === 0x11 || it === +1 || it === -1) {
   it;
-} else if (x === "hi") {
+} else if (it === "hi") {
   it;
-} else if (x === `there ${ 1 + 1 }`) {
+} else if (it === `there ${ 1 + 1 }`) {
   it;
-} else if (/\s+/.test(x)) {
+} else if (/\s+/.test(it)) {
   it;
-} else if (typeof x === "number" || typeof x === "boolean" || typeof x === "string") {
+} else if (typeof it === "number" || typeof it === "boolean" || typeof it === "string") {
   it;
-} else if (x instanceof Array || x instanceof Object || x instanceof Map || x instanceof Foo) {
+} else if (it instanceof Array || it instanceof Object || it instanceof Map || it instanceof Foo) {
   it;
-} else if (x === null || x === undefined) {
+} else if (it === null || it === undefined) {
   it;
 } else if (x || +x) {
   it;
-} else if (!(x === 1) || !x) {
+} else if (!(it === 1) || !x) {
   it;
-}
+}
\ No newline at end of file
diff --git a/test/fixtures/match/basic/expected.js b/test/fixtures/match/basic/expected.js
index d1f0004..6c0a0db 100644
--- a/test/fixtures/match/basic/expected.js
+++ b/test/fixtures/match/basic/expected.js
@@ -1,7 +1,7 @@
-const z = (_it => {
-  if (_it === 1) {
+const z = (it => {
+  if (it === 1) {
     return "one";
-  } else if (_it === 2) {
+  } else if (it === 2) {
     return "two";
   } else {
     return "idk";
diff --git a/test/fixtures/match/not/actual.js b/test/fixtures/match/not/actual.js
index 6148821..91a9037 100644
--- a/test/fixtures/match/not/actual.js
+++ b/test/fixtures/match/not/actual.js
@@ -1,5 +1,5 @@
 match x:
   | not 1 or not Number or not "hi":
     it
-  | not x or not 1 + 1 or not foo(bar):
+  | not it or not 1 + 1 or not foo(bar):
     it
diff --git a/test/fixtures/match/not/expected.js b/test/fixtures/match/not/expected.js
index 8cb3a7c..ed7793b 100644
--- a/test/fixtures/match/not/expected.js
+++ b/test/fixtures/match/not/expected.js
@@ -1,5 +1,7 @@
-if (!(x === 1) || !(typeof x === "number") || !(x === "hi")) {
+const it = x;
+
+if (!(it === 1) || !(typeof it === "number") || !(it === "hi")) {
   it;
-} else if (!x || !1 + 1 || !foo(bar)) {
+} else if (!it || !1 + 1 || !foo(bar)) {
   it;
 }
\ No newline at end of file
diff --git a/test/fixtures/match/obj-pattern/actual.js b/test/fixtures/match/obj-pattern/actual.js
index 5ca3636..8ec8e06 100644
--- a/test/fixtures/match/obj-pattern/actual.js
+++ b/test/fixtures/match/obj-pattern/actual.js
@@ -1,14 +1,14 @@
 match x:
-  | { a }:
+  | with { a }:
     a
-  | { a, b }:
+  | with { a, b }:
     a + b
-  | { a, b = 1 }:
+  | with { a, b = 1 }:
     a + b
-  | { a, b: { ba, bb = 1 }, c: { ca, cb: { cba } } }:
+  | with { a, b: { ba, bb = 1 }, c: { ca, cb: { cba } } }:
     a + ba + bb + ca + cba
   | 1 or 2 with { a, b: { c } }:
     a + c
-  | { a: { b: { c } } = otherObj }:
+  | with { a: { b: { c } } = otherObj }:
     c
-  //TODO: | { a, ...b }: b
+  //TODO: test `| { a, ...b }: b`
diff --git a/test/fixtures/match/obj-pattern/exec.js b/test/fixtures/match/obj-pattern/exec.js
index 65fbdb6..a3b272b 100644
--- a/test/fixtures/match/obj-pattern/exec.js
+++ b/test/fixtures/match/obj-pattern/exec.js
@@ -1,36 +1,36 @@
 assert.equal(
   1,
   match { a: 1 }:
-    | { a }:
+    | with { a }:
       a
 )
 assert.equal(
   undefined,
   match { b: 1 }:
-    | { a }:
+    | with { a }:
       a
 )
 assert.equal(
   3,
   match { a: 1 }:
-    | { a, b = 2 }:
+    | with { a, b = 2 }:
       a + b
 )
 assert.equal(
   undefined,
   match { b: 1 }:
-    | { a, b = 2 }:
+    | with { a, b = 2 }:
       a + b
 )
 assert.equal(
   3,
   match { a: 1, b: { c: 2 } }:
-    | { a, b: { c } }:
+    | with { a, b: { c } }:
       a + c
 )
 assert.equal(
   undefined,
   match { a: 1 }:
-    | { a, b: { c } }:
+    | with { a, b: { c } }:
       a + c
 )
diff --git a/test/fixtures/match/obj-pattern/expected.js b/test/fixtures/match/obj-pattern/expected.js
index 2302b8c..f9a9691 100644
--- a/test/fixtures/match/obj-pattern/expected.js
+++ b/test/fixtures/match/obj-pattern/expected.js
@@ -28,4 +28,4 @@ if (_hasProps(x, ["a"])) {
   const { a: { b: { c } } = otherObj } = x;
 
   c;
-} //TODO: | { a, ...b }: b
+} //TODO: test `| { a, ...b }: b`
diff --git a/test/fixtures/match/single-else-expr/expected.js b/test/fixtures/match/single-else-expr/expected.js
index 0c81fe4..80f4483 100644
--- a/test/fixtures/match/single-else-expr/expected.js
+++ b/test/fixtures/match/single-else-expr/expected.js
@@ -1,4 +1,4 @@
-const z = (_it => {
+const z = (it => {
   {
     try {} finally {}
     return "idk";

From 8cebb95822bb321a8d94601bc1d1d905c263aeb9 Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Fri, 9 Jun 2017 16:32:32 -0700
Subject: [PATCH 5/7] Disallow object and array literals, cleanup hasProps

---
 src/index.js                                  |  9 +++++-
 src/stdlib.js                                 | 14 ++++++----
 test/fixtures/match/arr-pattern/expected.js   |  8 ++----
 .../fixtures/match/illegal-arr-expr/actual.js |  2 ++
 .../match/illegal-arr-expr/options.json       |  3 ++
 .../fixtures/match/illegal-obj-expr/actual.js |  2 ++
 .../match/illegal-obj-expr/options.json       |  3 ++
 .../match/obj-arr-pattern-mixed/actual.js     |  3 ++
 .../match/obj-arr-pattern-mixed/exec.js       | 28 +++++++++++++++++++
 .../match/obj-arr-pattern-mixed/expected.js   |  9 ++++++
 test/fixtures/match/obj-pattern/expected.js   | 20 ++++++-------
 11 files changed, 76 insertions(+), 25 deletions(-)
 create mode 100644 test/fixtures/match/illegal-arr-expr/actual.js
 create mode 100644 test/fixtures/match/illegal-arr-expr/options.json
 create mode 100644 test/fixtures/match/illegal-obj-expr/actual.js
 create mode 100644 test/fixtures/match/illegal-obj-expr/options.json
 create mode 100644 test/fixtures/match/obj-arr-pattern-mixed/actual.js
 create mode 100644 test/fixtures/match/obj-arr-pattern-mixed/exec.js
 create mode 100644 test/fixtures/match/obj-arr-pattern-mixed/expected.js

diff --git a/src/index.js b/src/index.js
index dffb331..2def571 100644
--- a/src/index.js
+++ b/src/index.js
@@ -684,6 +684,8 @@ export default function (babel) {
       const fnAST = babel.template(fn.toString())({
         [helperName]: uid,
       });
+      fnAST._compact = true;
+      fnAST._generated = true;
       helpers.push(fnAST);
     }
     insertAfterImports(path, helpers);
@@ -850,6 +852,11 @@ export default function (babel) {
     } else if (path.isLiteral() || isUndefined(path) || isSignedNumber(path)) {
       const isEq = t.binaryExpression("===", argRef, path.node);
       path.replaceWith(isEq);
+    } else if (path.isObjectExpression() || path.isArrayExpression()) {
+      throw path.buildCodeFrameError(
+        "LightScript does not yet support matching on object or array literals. " +
+        "To destructure, use `with` (eg; `| with { foo, bar }: foo + bar`)."
+      );
     }
   }
 
@@ -896,7 +903,7 @@ export default function (babel) {
         }
       }
 
-      const isObjCall = t.callExpression(isObjUid, [argRef, t.arrayExpression(propsToCheck)]);
+      const isObjCall = t.callExpression(isObjUid, [argRef, ...propsToCheck]);
       test = buildAnd(test, isObjCall);
 
       for (const [ propName, childPatternPath, defaultObj = null ] of childPatterns) {
diff --git a/src/stdlib.js b/src/stdlib.js
index 434342e..fecdb00 100644
--- a/src/stdlib.js
+++ b/src/stdlib.js
@@ -12,12 +12,14 @@ export const lightscriptImports = {
 };
 
 export const runtimeHelpers = {
-  hasProps: function hasProps(obj, props) {
-    return (
-      obj != null &&
-      (typeof obj === "object" || typeof obj === "function") &&
-      props.filter(prop => prop in obj).length === props.length
-    );
+  hasProps: function hasProps(obj) {
+    if (obj == null) return false;
+    if (typeof obj !== "object" && typeof obj !== "function") return false;
+    let i = arguments.length;
+    while (--i > 0) {
+      if (!(arguments[i] in obj)) return false;
+    }
+    return true;
   },
   hasLength: function hasLength(arr, minLength, maxLength) {
     minLength = minLength || 0;
diff --git a/test/fixtures/match/arr-pattern/expected.js b/test/fixtures/match/arr-pattern/expected.js
index 97e2a6c..dd49872 100644
--- a/test/fixtures/match/arr-pattern/expected.js
+++ b/test/fixtures/match/arr-pattern/expected.js
@@ -1,8 +1,4 @@
-function _hasLength(arr, minLength, maxLength) {
-  minLength = minLength || 0;
-  maxLength = maxLength != null ? maxLength : Number.MAX_SAFE_INTEGER;
-  return arr != null && typeof arr !== "function" && arr.length === arr.length | 0 && arr.length >= minLength && arr.length <= maxLength;
-}
+function _hasLength(arr, minLength, maxLength) { minLength = minLength || 0; maxLength = maxLength != null ? maxLength : Number.MAX_SAFE_INTEGER; return arr != null && typeof arr !== "function" && arr.length === arr.length | 0 && arr.length >= minLength && arr.length <= maxLength; }
 
 if (_hasLength(x, 0, 0)) {
   const [] = x;
@@ -24,4 +20,4 @@ if (_hasLength(x, 0, 0)) {
   const [[b, d = 'e'], [g,, h], ...j] = x;
 
   [b, d, g, ...j].join('');
-}
+}
\ No newline at end of file
diff --git a/test/fixtures/match/illegal-arr-expr/actual.js b/test/fixtures/match/illegal-arr-expr/actual.js
new file mode 100644
index 0000000..cc430b1
--- /dev/null
+++ b/test/fixtures/match/illegal-arr-expr/actual.js
@@ -0,0 +1,2 @@
+match x:
+  | 1 or [a, b]: "not allowed"
diff --git a/test/fixtures/match/illegal-arr-expr/options.json b/test/fixtures/match/illegal-arr-expr/options.json
new file mode 100644
index 0000000..ebbcb4a
--- /dev/null
+++ b/test/fixtures/match/illegal-arr-expr/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "LightScript does not yet support matching on object or array literals. To destructure, use `with` (eg; `| with { foo, bar }: foo + bar`)."
+}
diff --git a/test/fixtures/match/illegal-obj-expr/actual.js b/test/fixtures/match/illegal-obj-expr/actual.js
new file mode 100644
index 0000000..b5d9aab
--- /dev/null
+++ b/test/fixtures/match/illegal-obj-expr/actual.js
@@ -0,0 +1,2 @@
+match x:
+  | 1 or { a, b: 1 }: "not allowed"
diff --git a/test/fixtures/match/illegal-obj-expr/options.json b/test/fixtures/match/illegal-obj-expr/options.json
new file mode 100644
index 0000000..ebbcb4a
--- /dev/null
+++ b/test/fixtures/match/illegal-obj-expr/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "LightScript does not yet support matching on object or array literals. To destructure, use `with` (eg; `| with { foo, bar }: foo + bar`)."
+}
diff --git a/test/fixtures/match/obj-arr-pattern-mixed/actual.js b/test/fixtures/match/obj-arr-pattern-mixed/actual.js
new file mode 100644
index 0000000..215ea74
--- /dev/null
+++ b/test/fixtures/match/obj-arr-pattern-mixed/actual.js
@@ -0,0 +1,3 @@
+match x:
+  | with { a, aa: [b, { c = 1 }, ...d] }:
+    d.concat(a + b + c)
diff --git a/test/fixtures/match/obj-arr-pattern-mixed/exec.js b/test/fixtures/match/obj-arr-pattern-mixed/exec.js
new file mode 100644
index 0000000..1601ab2
--- /dev/null
+++ b/test/fixtures/match/obj-arr-pattern-mixed/exec.js
@@ -0,0 +1,28 @@
+m(x) -> match x:
+  | with { a, aa: [b, { c = 1 }, ...d] }:
+    d.concat(a + b + c)
+
+assert.equal(
+  undefined,
+  m()
+)
+assert.equal(
+  undefined,
+  m({ a: 1 })
+)
+assert.equal(
+  undefined,
+  m({ a: 1, aa: [ 2 ] })
+)
+assert.deepEqual(
+  [4],
+  m({ a: 1, aa: [ 2, [ 3 ] ] })  // womp, arrays are objects
+)
+assert.deepEqual(
+  [5],
+  m({ a: 1, aa: [ 2, { c: 2 } ] })
+)
+assert.deepEqual(
+  [7, 5],
+  m({ a: 1, aa: [ 2, { c: 2 }, 7 ] })
+)
diff --git a/test/fixtures/match/obj-arr-pattern-mixed/expected.js b/test/fixtures/match/obj-arr-pattern-mixed/expected.js
new file mode 100644
index 0000000..71e95db
--- /dev/null
+++ b/test/fixtures/match/obj-arr-pattern-mixed/expected.js
@@ -0,0 +1,9 @@
+function _hasProps(obj) { if (obj == null) return false; if (typeof obj !== "object" && typeof obj !== "function") return false; var i = arguments.length; while (--i > 0) { if (!(arguments[i] in obj)) return false; } return true; }
+
+function _hasLength(arr, minLength, maxLength) { minLength = minLength || 0; maxLength = maxLength != null ? maxLength : Number.MAX_SAFE_INTEGER; return arr != null && typeof arr !== "function" && arr.length === arr.length | 0 && arr.length >= minLength && arr.length <= maxLength; }
+
+if (_hasProps(x, "a", "aa") && _hasLength(x.aa, 2) && _hasProps(x.aa[1])) {
+  const { a, aa: [b, { c = 1 }, ...d] } = x;
+
+  d.concat(a + b + c);
+}
\ No newline at end of file
diff --git a/test/fixtures/match/obj-pattern/expected.js b/test/fixtures/match/obj-pattern/expected.js
index f9a9691..5b13690 100644
--- a/test/fixtures/match/obj-pattern/expected.js
+++ b/test/fixtures/match/obj-pattern/expected.js
@@ -1,31 +1,27 @@
-function _hasProps(obj, props) {
-  return obj != null && (typeof obj === "object" || typeof obj === "function") && props.filter(function (prop) {
-    return prop in obj;
-  }).length === props.length;
-}
+function _hasProps(obj) { if (obj == null) return false; if (typeof obj !== "object" && typeof obj !== "function") return false; var i = arguments.length; while (--i > 0) { if (!(arguments[i] in obj)) return false; } return true; }
 
-if (_hasProps(x, ["a"])) {
+if (_hasProps(x, "a")) {
   const { a } = x;
 
   a;
-} else if (_hasProps(x, ["a", "b"])) {
+} else if (_hasProps(x, "a", "b")) {
   const { a, b } = x;
 
   a + b;
-} else if (_hasProps(x, ["a"])) {
+} else if (_hasProps(x, "a")) {
   const { a, b = 1 } = x;
 
   a + b;
-} else if (_hasProps(x, ["a", "b", "c"]) && _hasProps(x.b, ["ba"]) && _hasProps(x.c, ["ca", "cb"]) && _hasProps(x.c.cb, ["cba"])) {
+} else if (_hasProps(x, "a", "b", "c") && _hasProps(x.b, "ba") && _hasProps(x.c, "ca", "cb") && _hasProps(x.c.cb, "cba")) {
   const { a, b: { ba, bb = 1 }, c: { ca, cb: { cba } } } = x;
 
   a + ba + bb + ca + cba;
-} else if ((x === 1 || x === 2) && _hasProps(x, ["a", "b"]) && _hasProps(x.b, ["c"])) {
+} else if ((x === 1 || x === 2) && _hasProps(x, "a", "b") && _hasProps(x.b, "c")) {
   const { a, b: { c } } = x;
 
   a + c;
-} else if (_hasProps(x, []) && (_hasProps(x.a, ["b"]) && _hasProps(x.a.b, ["c"]) || _hasProps(otherObj, ["b"]) && _hasProps(otherObj.b, ["c"]))) {
+} else if (_hasProps(x) && (_hasProps(x.a, "b") && _hasProps(x.a.b, "c") || _hasProps(otherObj, "b") && _hasProps(otherObj.b, "c"))) {
   const { a: { b: { c } } = otherObj } = x;
 
   c;
-} //TODO: test `| { a, ...b }: b`
+} //TODO: test `| { a, ...b }: b`
\ No newline at end of file

From 350454b3a39a2c36dba613126a97f56ee295bf9b Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Sat, 10 Jun 2017 00:25:56 -0700
Subject: [PATCH 6/7] Prevent sibling 'it'

---
 src/index.js                                   | 15 ++++++++++++---
 .../match/illegal-sibling-no-as/actual.js      |  5 +++++
 .../match/illegal-sibling-no-as/options.json   |  3 +++
 test/fixtures/match/nested-it/actual.js        |  7 +++++++
 test/fixtures/match/nested-it/expected.js      | 18 ++++++++++++++++++
 test/fixtures/match/sibling-as/actual.js       |  5 +++++
 test/fixtures/match/sibling-as/expected.js     | 11 +++++++++++
 7 files changed, 61 insertions(+), 3 deletions(-)
 create mode 100644 test/fixtures/match/illegal-sibling-no-as/actual.js
 create mode 100644 test/fixtures/match/illegal-sibling-no-as/options.json
 create mode 100644 test/fixtures/match/nested-it/actual.js
 create mode 100644 test/fixtures/match/nested-it/expected.js
 create mode 100644 test/fixtures/match/sibling-as/actual.js
 create mode 100644 test/fixtures/match/sibling-as/expected.js

diff --git a/src/index.js b/src/index.js
index 2def571..c45a717 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1009,6 +1009,14 @@ export default function (babel) {
     }, null);
   }
 
+  function prependDeclaration(path, id, init, kind = "const") {
+    path.insertBefore(t.variableDeclaration(kind, [
+      t.variableDeclarator(id, init)
+    ]));
+    const constPath = path.getSibling(path.key - 1);
+    path.scope.registerBinding(kind, constPath);
+  }
+
   // TYPE DEFINITIONS
   definePluginType("ForInArrayStatement", {
     visitor: ["idx", "elem", "array", "body"],
@@ -1578,9 +1586,10 @@ export default function (babel) {
           argRef = discriminant;
         } else {
           argRef = alias;
-          path.insertBefore(t.variableDeclaration("const", [
-            t.variableDeclarator(argRef, discriminant)
-          ]));
+          if (path.scope.hasOwnBinding(argRef.name)) {
+            throw path.buildCodeFrameError("Cannot re-use `it` binding in the same scope. Try a new shorthand name (eg; `match foo as x:`).");
+          }
+          prependDeclaration(path, argRef, discriminant);
         }
 
         const matchBody = transformMatchCases(argRef, path.get("cases"));
diff --git a/test/fixtures/match/illegal-sibling-no-as/actual.js b/test/fixtures/match/illegal-sibling-no-as/actual.js
new file mode 100644
index 0000000..00273c1
--- /dev/null
+++ b/test/fixtures/match/illegal-sibling-no-as/actual.js
@@ -0,0 +1,5 @@
+match foo():
+  | 1: "ok"
+
+match bar():
+  | 2: "oops"
diff --git a/test/fixtures/match/illegal-sibling-no-as/options.json b/test/fixtures/match/illegal-sibling-no-as/options.json
new file mode 100644
index 0000000..1eea700
--- /dev/null
+++ b/test/fixtures/match/illegal-sibling-no-as/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "Cannot re-use `it` binding in the same scope. Try a new shorthand name (eg; `match foo as x:`)."
+}
diff --git a/test/fixtures/match/nested-it/actual.js b/test/fixtures/match/nested-it/actual.js
new file mode 100644
index 0000000..5770bbd
--- /dev/null
+++ b/test/fixtures/match/nested-it/actual.js
@@ -0,0 +1,7 @@
+match foo():
+  | 1:
+    match it:
+      | 2: it
+  | with { x }:
+    match x:
+      | 2: it
diff --git a/test/fixtures/match/nested-it/expected.js b/test/fixtures/match/nested-it/expected.js
new file mode 100644
index 0000000..83dfd10
--- /dev/null
+++ b/test/fixtures/match/nested-it/expected.js
@@ -0,0 +1,18 @@
+function _hasProps(obj) { if (obj == null) return false; if (typeof obj !== "object" && typeof obj !== "function") return false; var i = arguments.length; while (--i > 0) { if (!(arguments[i] in obj)) return false; } return true; }
+
+const it = foo();
+
+if (it === 1) {
+  const it = it;
+
+  if (it === 2) {
+      it;
+    }
+} else if (_hasProps(it, "x")) {
+  const { x } = it;
+  const it = x;
+
+  if (it === 2) {
+      it;
+    }
+}
\ No newline at end of file
diff --git a/test/fixtures/match/sibling-as/actual.js b/test/fixtures/match/sibling-as/actual.js
new file mode 100644
index 0000000..8e8e8b4
--- /dev/null
+++ b/test/fixtures/match/sibling-as/actual.js
@@ -0,0 +1,5 @@
+match foo():
+  | 1: "ok"
+
+match bar() as x:
+  | 2: "ok 2"
diff --git a/test/fixtures/match/sibling-as/expected.js b/test/fixtures/match/sibling-as/expected.js
new file mode 100644
index 0000000..721faba
--- /dev/null
+++ b/test/fixtures/match/sibling-as/expected.js
@@ -0,0 +1,11 @@
+const it = foo();
+
+if (it === 1) {
+    "ok";
+  }
+
+const x = bar();
+
+if (x === 2) {
+    "ok 2";
+  }
\ No newline at end of file

From 1e720c158804b725d5eee440ff4cbd104e74390a Mon Sep 17 00:00:00 2001
From: Alex Rattray <rattray.alex@gmail.com>
Date: Sat, 10 Jun 2017 12:05:11 -0700
Subject: [PATCH 7/7] Allow sibling matches to use it

---
 src/index.js                                  | 28 +++++++++++--------
 .../match/illegal-sibling-no-as/options.json  |  3 --
 test/fixtures/match/implicit-return/actual.js |  9 ++++++
 .../match/implicit-return/expected.js         | 16 +++++++++++
 test/fixtures/match/nested-it/expected.js     | 20 +++++++------
 test/fixtures/match/shadow-it/actual.js       |  6 ++++
 test/fixtures/match/shadow-it/exec.js         |  8 ++++++
 test/fixtures/match/shadow-it/expected.js     | 12 ++++++++
 .../sibling-no-as-implicit-returns/actual.js  |  6 ++++
 .../expected.js                               | 15 ++++++++++
 .../actual.js                                 |  0
 test/fixtures/match/sibling-no-as/expected.js | 13 +++++++++
 12 files changed, 113 insertions(+), 23 deletions(-)
 delete mode 100644 test/fixtures/match/illegal-sibling-no-as/options.json
 create mode 100644 test/fixtures/match/implicit-return/actual.js
 create mode 100644 test/fixtures/match/implicit-return/expected.js
 create mode 100644 test/fixtures/match/shadow-it/actual.js
 create mode 100644 test/fixtures/match/shadow-it/exec.js
 create mode 100644 test/fixtures/match/shadow-it/expected.js
 create mode 100644 test/fixtures/match/sibling-no-as-implicit-returns/actual.js
 create mode 100644 test/fixtures/match/sibling-no-as-implicit-returns/expected.js
 rename test/fixtures/match/{illegal-sibling-no-as => sibling-no-as}/actual.js (100%)
 create mode 100644 test/fixtures/match/sibling-no-as/expected.js

diff --git a/src/index.js b/src/index.js
index c45a717..e4659d0 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1009,7 +1009,7 @@ export default function (babel) {
     }, null);
   }
 
-  function prependDeclaration(path, id, init, kind = "const") {
+  function insertDeclarationBefore(path, id, init, kind = "const") {
     path.insertBefore(t.variableDeclaration(kind, [
       t.variableDeclarator(id, init)
     ]));
@@ -1581,19 +1581,23 @@ export default function (babel) {
         const { discriminant } = path.node;
         const alias = path.node.alias || t.identifier("it");
 
-        let argRef;
-        if (t.isIdentifier(discriminant) && !containsAliasReference(path, alias)) {
-          argRef = discriminant;
-        } else {
-          argRef = alias;
-          if (path.scope.hasOwnBinding(argRef.name)) {
-            throw path.buildCodeFrameError("Cannot re-use `it` binding in the same scope. Try a new shorthand name (eg; `match foo as x:`).");
-          }
-          prependDeclaration(path, argRef, discriminant);
-        }
-
+        const argRef = t.isIdentifier(discriminant) && !containsAliasReference(path, alias)
+          ? discriminant
+          : alias;
         const matchBody = transformMatchCases(argRef, path.get("cases"));
+
         path.replaceWith(matchBody);
+
+        // insert eg; `const it = foo()` above the body,
+        // possibly wrapping both in an anonymous block.
+        if (argRef !== discriminant) {
+          if (path.scope.hasBinding(alias.name)) {
+            // wrap in anonymous block
+            path.replaceWith(t.blockStatement([path.node]));
+            path = path.get("body.0");
+          }
+          insertDeclarationBefore(path, argRef, discriminant);
+        }
       },
 
     });
diff --git a/test/fixtures/match/illegal-sibling-no-as/options.json b/test/fixtures/match/illegal-sibling-no-as/options.json
deleted file mode 100644
index 1eea700..0000000
--- a/test/fixtures/match/illegal-sibling-no-as/options.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "throws": "Cannot re-use `it` binding in the same scope. Try a new shorthand name (eg; `match foo as x:`)."
-}
diff --git a/test/fixtures/match/implicit-return/actual.js b/test/fixtures/match/implicit-return/actual.js
new file mode 100644
index 0000000..21be344
--- /dev/null
+++ b/test/fixtures/match/implicit-return/actual.js
@@ -0,0 +1,9 @@
+f() ->
+  match foo():
+    | 1:
+      "ok"
+    | 2:
+      bar()
+      match baz():
+        | 3:
+          qux()
diff --git a/test/fixtures/match/implicit-return/expected.js b/test/fixtures/match/implicit-return/expected.js
new file mode 100644
index 0000000..d859902
--- /dev/null
+++ b/test/fixtures/match/implicit-return/expected.js
@@ -0,0 +1,16 @@
+function f() {
+  const it = foo();
+
+  if (it === 1) {
+    return "ok";
+  } else if (it === 2) {
+    bar();
+    {
+      const it = baz();
+
+      if (it === 3) {
+        return qux();
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/fixtures/match/nested-it/expected.js b/test/fixtures/match/nested-it/expected.js
index 83dfd10..16efb21 100644
--- a/test/fixtures/match/nested-it/expected.js
+++ b/test/fixtures/match/nested-it/expected.js
@@ -3,16 +3,20 @@ function _hasProps(obj) { if (obj == null) return false; if (typeof obj !== "obj
 const it = foo();
 
 if (it === 1) {
-  const it = it;
+  {
+    const it = it;
 
-  if (it === 2) {
-      it;
-    }
+    if (it === 2) {
+        it;
+      }
+  }
 } else if (_hasProps(it, "x")) {
   const { x } = it;
-  const it = x;
+  {
+    const it = x;
 
-  if (it === 2) {
-      it;
-    }
+    if (it === 2) {
+        it;
+      }
+  }
 }
\ No newline at end of file
diff --git a/test/fixtures/match/shadow-it/actual.js b/test/fixtures/match/shadow-it/actual.js
new file mode 100644
index 0000000..0295238
--- /dev/null
+++ b/test/fixtures/match/shadow-it/actual.js
@@ -0,0 +1,6 @@
+it = "good"
+f() ->
+  match "bad":
+    | true: true
+
+  it
diff --git a/test/fixtures/match/shadow-it/exec.js b/test/fixtures/match/shadow-it/exec.js
new file mode 100644
index 0000000..3911e73
--- /dev/null
+++ b/test/fixtures/match/shadow-it/exec.js
@@ -0,0 +1,8 @@
+it = "good"
+f() ->
+  match "bad":
+    | true: true
+
+  it
+
+assert.equal("good", f())
diff --git a/test/fixtures/match/shadow-it/expected.js b/test/fixtures/match/shadow-it/expected.js
new file mode 100644
index 0000000..ac23c90
--- /dev/null
+++ b/test/fixtures/match/shadow-it/expected.js
@@ -0,0 +1,12 @@
+const it = "good";
+
+function f() {
+  {
+    const it = "bad";
+
+    if (it === true) {
+        true;
+      }
+  }
+  return it;
+}
\ No newline at end of file
diff --git a/test/fixtures/match/sibling-no-as-implicit-returns/actual.js b/test/fixtures/match/sibling-no-as-implicit-returns/actual.js
new file mode 100644
index 0000000..995b453
--- /dev/null
+++ b/test/fixtures/match/sibling-no-as-implicit-returns/actual.js
@@ -0,0 +1,6 @@
+f() ->
+  match foo():
+    | 1: "ok"
+
+  match bar():
+    | 2: "oops"
diff --git a/test/fixtures/match/sibling-no-as-implicit-returns/expected.js b/test/fixtures/match/sibling-no-as-implicit-returns/expected.js
new file mode 100644
index 0000000..41827b9
--- /dev/null
+++ b/test/fixtures/match/sibling-no-as-implicit-returns/expected.js
@@ -0,0 +1,15 @@
+function f() {
+  const it = foo();
+
+  if (it === 1) {
+      "ok";
+    }
+
+  {
+    const it = bar();
+
+    if (it === 2) {
+        return "oops";
+      }
+  }
+}
diff --git a/test/fixtures/match/illegal-sibling-no-as/actual.js b/test/fixtures/match/sibling-no-as/actual.js
similarity index 100%
rename from test/fixtures/match/illegal-sibling-no-as/actual.js
rename to test/fixtures/match/sibling-no-as/actual.js
diff --git a/test/fixtures/match/sibling-no-as/expected.js b/test/fixtures/match/sibling-no-as/expected.js
new file mode 100644
index 0000000..934e5c4
--- /dev/null
+++ b/test/fixtures/match/sibling-no-as/expected.js
@@ -0,0 +1,13 @@
+const it = foo();
+
+if (it === 1) {
+    "ok";
+  }
+
+{
+  const it = bar();
+
+  if (it === 2) {
+      "oops";
+    }
+}
\ No newline at end of file