Added checking for switch statements with multiple default clauses.

Author: DanielRosenwasser

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:
+ }
+}