Add comments

src/compiler/checker.ts

@@ -11119,6 +11119,7 @@ module ts {
                     ? Diagnostics.An_ambient_module_declaration_is_only_allowed_at_the_top_level_in_a_file
                     : Diagnostics.A_namespace_declaration_is_only_allowed_in_a_namespace_or_module;
                 if (checkGrammarModuleElementContext(node, contextErrorMessage)) {
+                    // If we hit a module declaration in an illegal context, just bail out to avoid cascading errors.
                     return;
                 }
 
@@ -11235,6 +11236,7 @@ module ts {
 
         function checkImportDeclaration(node: ImportDeclaration) {
             if (checkGrammarModuleElementContext(node, Diagnostics.An_import_declaration_can_only_be_used_in_a_namespace_or_module)) {
+                // If we hit an import declaration in an illegal context, just bail out to avoid cascading errors.
                 return;
             }
             if (!checkGrammarImportDeclarationNameInStrictMode(node) && !checkGrammarDecorators(node) && !checkGrammarModifiers(node) && (node.flags & NodeFlags.Modifier)) {
@@ -11260,6 +11262,7 @@ module ts {
 
         function checkImportEqualsDeclaration(node: ImportEqualsDeclaration) {
             if (checkGrammarModuleElementContext(node, Diagnostics.An_import_declaration_can_only_be_used_in_a_namespace_or_module)) {
+                // If we hit an import declaration in an illegal context, just bail out to avoid cascading errors.
                 return;
             }
 
@@ -11295,6 +11298,7 @@ module ts {
 
         function checkExportDeclaration(node: ExportDeclaration) {
             if (checkGrammarModuleElementContext(node, Diagnostics.An_export_declaration_can_only_be_used_in_a_module)) {
+                // If we hit an export in an illegal context, just bail out to avoid cascading errors.
                 return;
             }
 
@@ -11338,6 +11342,7 @@ module ts {
 
         function checkExportAssignment(node: ExportAssignment) {
             if (checkGrammarModuleElementContext(node, Diagnostics.An_export_assignment_can_only_be_used_in_a_module)) {
+                // If we hit an export assignment in an illegal context, just bail out to avoid cascading errors.
                 return;
             }
 

src/compiler/parser.ts

@@ -1770,25 +1770,25 @@ module ts {
         }
 
         function parseRightSideOfDot(allowIdentifierNames: boolean): Identifier {
-            // Technically a keyword is valid here as all keywords are identifier names.
+            // Technically a keyword is valid here as all identifiers and keywords are identifier names.
-            // However, often we'll encounter this in error situations when the keyword
+            // However, often we'll encounter this in error situations when the identifier or keyword
             // is actually starting another valid construct.
             //
             // So, we check for the following specific case:
             //
             //      name.
-            //      keyword identifierNameOrKeyword
+            //      identifierOrKeyword identifierNameOrKeyword
             //
             // Note: the newlines are important here.  For example, if that above code
             // were rewritten into:
             //
-            //      name.keyword
+            //      name.identifierOrKeyword
             //      identifierNameOrKeyword
             //
             // Then we would consider it valid.  That's because ASI would take effect and
-            // the code would be implicitly: "name.keyword; identifierNameOrKeyword".
+            // the code would be implicitly: "name.identifierOrKeyword; identifierNameOrKeyword".
             // In the first case though, ASI will not take effect because there is not a
-            // line terminator after the keyword.
+            // line terminator after the identifier or keyword.
             if (scanner.hasPrecedingLineBreak() && isIdentifierOrKeyword()) {
                 let matchesPattern = lookAhead(nextTokenIsIdentifierOrKeywordOnSameLine);