statically check whether a contract always fails

codemix · Dec 4, 2015 · a3e4fb2 · a3e4fb2
1 parent a7e2997
commit a3e4fb2
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Showing 4 changed files with 30 additions and 10 deletions.
diff --git a/src/index.js b/src/index.js
@@ -80,7 +80,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
         message = t.stringLiteral(`Function ${name}precondition failed: ${generate(condition.node).code}`);
       }
       path.replaceWith(guard({
-        condition,
+        condition: staticCheck(condition),
         message
       }));
       return;
@@ -102,7 +102,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
           message = t.stringLiteral(`Function ${name}precondition failed: ${generate(condition.node).code}`);
         }
         statement.replaceWith(guard({
-          condition,
+          condition: staticCheck(condition),
           message
         }));
       }
@@ -135,7 +135,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
         message = t.stringLiteral(`Function ${name}postcondition failed: ${generate(condition.node).code}`);
       }
       conditions.push(guard({
-        condition,
+        condition: staticCheck(condition),
         message
       }));
     }
@@ -167,7 +167,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
             message = t.stringLiteral(`Function ${name}postcondition failed: ${generate(condition.node).code}`);
           }
           statement.replaceWith(guard({
-            condition,
+            condition: staticCheck(condition),
             message
           }));
         }
@@ -206,7 +206,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
         message = t.stringLiteral(`Assertion failed: ${generate(condition.node).code}`);
       }
       path.replaceWith(guard({
-        condition,
+        condition: staticCheck(condition),
         message
       }));
       return;
@@ -231,7 +231,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
           message = t.stringLiteral(`Assertion failed: ${generate(condition.node).code}`);
         }
         statement.replaceWith(guard({
-          condition,
+          condition: staticCheck(condition),
           message
         }));
       }
@@ -263,7 +263,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
         message = t.stringLiteral(`Function ${name}invariant failed: ${generate(condition.node).code}`);
       }
       conditions.push(guard({
-        condition,
+        condition: staticCheck(condition),
         message
       }));
     }
@@ -284,7 +284,7 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
             message = t.stringLiteral(`Function ${name}invariant failed: ${generate(condition.node).code}`);
           }
           statement.replaceWith(guard({
-            condition,
+            condition: staticCheck(condition),
             message
           }));
         }
@@ -311,6 +311,15 @@ export default function ({types: t, template, options}: PluginParams): Plugin {
     };
   }
 
+  function staticCheck (expression: NodePath): NodePath {
+    const {confident, value} = expression.evaluate();
+    if (confident && !value) {
+      throw expression.buildCodeFrameError(`Contract always fails.`);
+    }
+
+    return expression;
+  }
+
   return {
     visitor: {
       Function (fn: NodePath, {opts}): void {

diff --git a/test/fixtures/bad-assert-no-function.js b/test/fixtures/bad-assert-no-function.js
@@ -1,5 +1,9 @@
-assert: false;
+assert: fail();
 
 export default function demo (input) {
   assert: input.length > 0;
+}
+
+function fail () {
+  return false;
 }
diff --git a/test/fixtures/bad-precondition-always-false.js b/test/fixtures/bad-precondition-always-false.js
@@ -0,0 +1,6 @@
+export default function demo (input) {
+  pre: {
+    false;
+  }
+  return input.length;
+}
diff --git a/test/index.js b/test/index.js
@@ -12,6 +12,7 @@ else {
 }
 
 describe('Typecheck', function () {
+  failStatic('bad-precondition-always-false', 'foobar');
   ok('class', 'first', 'second');
   ok('old-value', 5, 5);
   failWith(`Function "add5" postcondition failed: input === old(input) + 5`, 'old-value', 5, 10);
@@ -33,7 +34,7 @@ describe('Typecheck', function () {
   ok('assert-with-message', 'hello');
   failWith(`input cannot be empty`, 'assert-with-message', '');
   ok('assert-no-function', 'hello');
-  failWith(`Assertion failed: false`, 'bad-assert-no-function', 'hello');
+  failWith(`Assertion failed: fail()`, 'bad-assert-no-function', 'hello');
   ok('example-2', 1, 2);
   ok('example-2', 1);
   ok('example-2', 0, 2);