Report error for block scope function declaration in ES5

Author: sheetalkamat

src/compiler/binder.ts

@@ -1125,6 +1125,35 @@ namespace ts {
  }
  }
 
+ function getStrictModeBlockScopeFunctionDeclarationMessage(node: Node) {
+ // Provide specialized messages to help the user understand why we think they're in
+ // strict mode.
+ if (getContainingClass(node)) {
+ return Diagnostics.In_ES5_or_lower_function_declarations_are_not_allowed_in_block_scope_Class_definitions_are_automatically_in_strict_mode;
+ }
+
+ if (file.externalModuleIndicator) {
+ return Diagnostics.In_ES5_or_lower_function_declarations_are_not_allowed_in_block_scope_Modules_are_automatically_in_strict_mode;
+ }
+
+ return Diagnostics.In_ES5_or_lower_function_declarations_are_not_allowed_in_block_scope_in_strict_mode;
+ }
+
+ function checkStrictModeFunctionDeclaration(node: FunctionDeclaration) {
+ if (getEmitScriptTarget(options) < ScriptTarget.ES6) {
+ // Report error if function is not top level function declaration
+ if (blockScopeContainer.kind !== SyntaxKind.SourceFile &&
+ blockScopeContainer.kind !== SyntaxKind.ModuleDeclaration &&
+ !isFunctionLike(blockScopeContainer)) {
+ // We check first if the name is inside class declaration or class expression; if so give explicit message
+ // otherwise report generic error message.
+ const errorSpan = getErrorSpanForNode(file, node);
+ file.bindDiagnostics.push(createFileDiagnostic(file, errorSpan.start, errorSpan.length,
+ getStrictModeBlockScopeFunctionDeclarationMessage(node)));
+ }
+ }
+ }
+
  function checkStrictModeNumericLiteral(node: LiteralExpression) {
  if (inStrictMode && node.isOctalLiteral) {
  file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Octal_literals_are_not_allowed_in_strict_mode));
@@ -1641,6 +1670,7 @@ namespace ts {
 
  checkStrictModeFunctionName(<FunctionDeclaration>node);
  if (inStrictMode) {
+ checkStrictModeFunctionDeclaration(node);
  bindBlockScopedDeclaration(node, SymbolFlags.Function, SymbolFlags.FunctionExcludes);
  }
  else {

src/compiler/diagnosticMessages.json

@@ -811,6 +811,18 @@
  "category": "Error",
  "code": 1249
  },
+ "In ES5 or lower, function declarations are not allowed in block scope in strict mode.": {
+ "category": "Error",
+ "code": 1250
+ },
+ "In ES5 or lower, function declarations are not allowed in block scope. Class definitions are automatically in strict mode.": {
+ "category": "Error",
+ "code": 1251
+ },
+ "In ES5 or lower, function declarations are not allowed in block scope. Modules are automatically in strict mode.": {
+ "category": "Error",
+ "code": 1252
+ },
  "'with' statements are not allowed in an async function block.": {
  "category": "Error",
  "code": 1300

tests/baselines/reference/blockScopedFunctionDeclarationStrictES5.errors.txt

@@ -1,10 +1,13 @@
+tests/cases/compiler/blockScopedFunctionDeclarationStrictES5.ts(3,14): error TS1250: In ES5 or lower, function declarations are not allowed in block scope in strict mode.
 tests/cases/compiler/blockScopedFunctionDeclarationStrictES5.ts(6,1): error TS2304: Cannot find name 'foo'.
 
 
-==== tests/cases/compiler/blockScopedFunctionDeclarationStrictES5.ts (1 errors) ====
+==== tests/cases/compiler/blockScopedFunctionDeclarationStrictES5.ts (2 errors) ====
  "use strict";
  if (true) {
  function foo() { } // Error to declare function in block scope
+ ~~~
+!!! error TS1250: In ES5 or lower, function declarations are not allowed in block scope in strict mode.
  foo(); // This call should be ok
  }
  foo(); // Error to find name foo