Increase test coverage (#175)

* Increase test coverage

* Test for error when binding `this` in destructuring pattern

* Ignore coverage of inAsync check in parseAwait - already checked externally

* Ignore coverage of default case in checkPropClash

* Remove unused parameter isAsync from parseParenAndDistinguishExpression

* Ignore coverage of an `else` branch in flowParseTypeParameterDeclaration

* Flow: remove unused parameters to flowParseTypeAnnotatableIdentifier

* Flow: ignore coverage of pass-through throw statement in parseConditional

* Flow: Add test for error on property with type param

* Flow: ignore coverage of pass-through throw statements in parseMaybeAssign, parseArrow

* Add test for error on XML-style comment in module code

* Update test for error on method in object pattern

* Test for error: "Only '=' operator can be used for specifying default value"

src/parser/expression.js

@@ -45,6 +45,7 @@ pp.checkPropClash = function (prop, propHash) {
       name = String(key.value);
       break;
 
+    // istanbul ignore next: non-computed property keys are always one of the above
     default:
       return;
   }
@@ -555,7 +556,7 @@ pp.parseParenExpression = function () {
   return val;
 };
 
-pp.parseParenAndDistinguishExpression = function (startPos, startLoc, canBeArrow, isAsync) {
+pp.parseParenAndDistinguishExpression = function (startPos, startLoc, canBeArrow) {
   startPos = startPos || this.state.start;
   startLoc = startLoc || this.state.startLoc;
 
@@ -597,15 +598,11 @@ pp.parseParenAndDistinguishExpression = function (startPos, startLoc, canBeArrow
       if (param.extra && param.extra.parenthesized) this.unexpected(param.extra.parenStart);
     }
 
-    return this.parseArrowExpression(arrowNode, exprList, isAsync);
+    return this.parseArrowExpression(arrowNode, exprList);
   }
 
   if (!exprList.length) {
-    if (isAsync) {
-      return;
-    } else {
-      this.unexpected(this.state.lastTokStart);
-    }
+    this.unexpected(this.state.lastTokStart);
   }
   if (optionalCommaStart) this.unexpected(optionalCommaStart);
   if (spreadStart) this.unexpected(spreadStart);
@@ -1025,6 +1022,7 @@ pp.parseIdentifier = function (liberal) {
 // Parses await expression inside async function.
 
 pp.parseAwait = function (node) {
+  // istanbul ignore next: this condition is checked at the call site so won't be hit here
   if (!this.state.inAsync) {
     this.unexpected();
   }

src/parser/statement.js

@@ -670,7 +670,6 @@ pp.parseClassBody = function (node) {
 
     method.static = isMaybeStatic && !this.match(tt.parenL);
     if (method.static) {
-      if (isGenerator) this.unexpected();
       isGenerator = this.eat(tt.star);
       this.parsePropertyName(method);
     }

src/plugins/flow.js

@@ -207,7 +207,7 @@ pp.flowParseTypeParameter = function () {
 
   let variance = this.flowParseVariance();
 
-  let ident = this.flowParseTypeAnnotatableIdentifier(false, false);
+  let ident = this.flowParseTypeAnnotatableIdentifier();
   node.name = ident.name;
   node.variance = variance;
   node.bound = ident.typeAnnotation;
@@ -227,6 +227,7 @@ pp.flowParseTypeParameterDeclaration = function () {
 
   this.state.inType = true;
 
+  // istanbul ignore else: this condition is already checked at all call sites
   if (this.isRelational("<") || this.match(tt.jsxTagStart)) {
     this.next();
   } else {
@@ -705,26 +706,12 @@ pp.flowParseTypeAnnotation = function () {
   return this.finishNode(node, "TypeAnnotation");
 };
 
-pp.flowParseTypeAnnotatableIdentifier = function (requireTypeAnnotation, canBeOptionalParam) {
-
+pp.flowParseTypeAnnotatableIdentifier = function () {
   let ident = this.parseIdentifier();
-  let isOptionalParam = false;
-
-  if (canBeOptionalParam && this.eat(tt.question)) {
-    this.expect(tt.question);
-    isOptionalParam = true;
-  }
-
-  if (requireTypeAnnotation || this.match(tt.colon)) {
+  if (this.match(tt.colon)) {
     ident.typeAnnotation = this.flowParseTypeAnnotation();
     this.finishNode(ident, ident.type);
   }
-
-  if (isOptionalParam) {
-    ident.optional = true;
-    this.finishNode(ident, ident.type);
-  }
-
   return ident;
 };
 
@@ -824,6 +811,7 @@ export default function (instance) {
             refNeedsArrowPos.start = err.pos || this.state.start;
             return expr;
           } else {
+            // istanbul ignore next: no such error is expected
             throw err;
           }
         }
@@ -1208,6 +1196,7 @@ export default function (instance) {
             this.state = state;
             jsxError = err;
           } else {
+            // istanbul ignore next: no such error is expected
             throw err;
           }
         }
@@ -1262,6 +1251,7 @@ export default function (instance) {
           if (err instanceof SyntaxError) {
             this.state = state;
           } else {
+            // istanbul ignore next: no such error is expected
             throw err;
           }
         }

src/plugins/jsx/index.js

@@ -365,6 +365,7 @@ pp.jsxParseElementAt = function(startPos, startLoc) {
 
           break;
 
+        // istanbul ignore next - should never happen
         default:
           this.unexpected();
       }