Added checking for switch statements with multiple default clauses.

src/compiler/core.ts

@@ -19,7 +19,9 @@ module ts {
         if (array) {
             var len = array.length;
             for (var i = 0; i < len; i++) {
-                if (array[i] === value) return true;
+                if (array[i] === value) {
+                    return true;
+                }
             }
         }
         return false;
@@ -29,7 +31,9 @@ module ts {
         if (array) {
             var len = array.length;
             for (var i = 0; i < len; i++) {
-                if (array[i] === value) return i;
+                if (array[i] === value) {
+                    return i;
+                }
             }
         }
         return -1;
@@ -41,7 +45,9 @@ module ts {
             result = [];
             for (var i = 0, len = array.length; i < len; i++) {
                 var item = array[i];
-                if (f(item)) result.push(item);
+                if (f(item)) {
+                    result.push(item);
+                }
             }
         }
         return result;

src/compiler/diagnosticInformationMap.generated.ts

@@ -98,6 +98,7 @@ module ts {
         Type_expected: { code: -9999999, category: DiagnosticCategory.Error, key: "Type expected." },
         A_constructor_implementation_cannot_be_declared_in_an_ambient_context: { code: 1111, category: DiagnosticCategory.Error, key: "A constructor implementation cannot be declared in an ambient context." },
         A_class_member_cannot_be_declared_optional: { code: 1112, category: DiagnosticCategory.Error, key: "A class member cannot be declared optional." },
+        A_default_clause_cannot_appear_more_than_once_in_a_switch_statement: { code: 1113, category: DiagnosticCategory.Error, key: "A 'default' clause cannot appear more than once in a 'switch' statement." },
         Duplicate_identifier_0: { code: 2000, category: DiagnosticCategory.Error, key: "Duplicate identifier '{0}'." },
         new_T_cannot_be_used_to_create_an_array_Use_new_Array_T_instead: { code: 2068, category: DiagnosticCategory.Error, key: "'new T[]' cannot be used to create an array. Use 'new Array<T>()' instead." },
         Multiple_constructor_implementations_are_not_allowed: { code: 2070, category: DiagnosticCategory.Error, key: "Multiple constructor implementations are not allowed." },

src/compiler/diagnosticMessages.json

@@ -384,7 +384,10 @@
         "category": "Error",
         "code": 1112
     },
-    
+    "A 'default' clause cannot appear more than once in a 'switch' statement.": {
+        "category": "Error",
+        "code": 1113
+    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",

src/compiler/parser.ts

@@ -766,7 +766,7 @@ module ts {
             return false;
         }
 
-        // Parses a list of elements
+        // Parses a semicolon-delimited list of elements
         function parseList<T extends Node>(kind: ParsingContext, parseElement: () => T): NodeArray<T> {
             var saveParsingContext = parsingContext;
             parsingContext |= 1 << kind;
@@ -789,7 +789,7 @@ module ts {
             return result;
         }
 
-        // Parses a comma delimited list of elements
+        // Parses a comma-delimited list of elements
         function parseDelimitedList<T extends Node>(kind: ParsingContext, parseElement: () => T, trailingCommaBehavior: TrailingCommaBehavior): NodeArray<T> {
             var saveParsingContext = parsingContext;
             parsingContext |= 1 << kind;
@@ -2063,6 +2063,13 @@ module ts {
             parseExpected(SyntaxKind.OpenBraceToken);
             node.clauses = parseList(ParsingContext.SwitchClauses, parseCaseOrDefaultClause);
             parseExpected(SyntaxKind.CloseBraceToken);
+
+            // Error on duplicate 'default' clauses.
+            var defaultClauses = filter(node.clauses, clause => clause.kind === SyntaxKind.DefaultClause);
+            for (var i = 1, len = defaultClauses.length; i < len; i++) {
+                grammarErrorOnNode(defaultClauses[i], Diagnostics.A_default_clause_cannot_appear_more_than_once_in_a_switch_statement);
+            }
+
             return finishNode(node);
         }
 

tests/baselines/reference/switchStatementsWithMultipleDefaults.errors.txt

@@ -0,0 +1,37 @@
+==== tests/cases/compiler/switchStatementsWithMultipleDefaults.ts (4 errors) ====
+    
+    var x = 10;
+    
+    switch (x) {
+        case 1:
+        case 2:
+        default:    // No issues.
+            break;
+        default:    // Error; second 'default' clause.
+        ~~~~~~~~
+!!! A 'default' clause cannot appear more than once in a 'switch' statement.
+        default:    // Error; third 'default' clause.
+        ~~~~~~~~
+!!! A 'default' clause cannot appear more than once in a 'switch' statement.
+        case 3:
+            x *= x;
+    }
+    
+    switch (x) {
+        default:    // No issues.
+            break;
+        case 100:
+            switch (x * x) {
+                default:    // No issues.
+                default:    // Error; second 'default' clause.
+                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+                    break;
+    ~~~~~~~~~~~~~~~~~~~~~~
+!!! A 'default' clause cannot appear more than once in a 'switch' statement.
+                case 10000:
+                    x /= x;
+                default:
+                ~~~~~~~~
+!!! A 'default' clause cannot appear more than once in a 'switch' statement.
+            }
+    }

tests/cases/compiler/switchStatementsWithMultipleDefaults.ts

@@ -0,0 +1,27 @@
+
+var x = 10;
+
+switch (x) {
+    case 1:
+    case 2:
+    default:    // No issues.
+        break;
+    default:    // Error; second 'default' clause.
+    default:    // Error; third 'default' clause.
+    case 3:
+        x *= x;
+}
+
+switch (x) {
+    default:    // No issues.
+        break;
+    case 100:
+        switch (x * x) {
+            default:    // No issues.
+            default:    // Error; second 'default' clause.
+                break;
+            case 10000:
+                x /= x;
+            default:
+        }
+}