remove obsolete special case logic

src/Module.js

@@ -397,34 +397,6 @@ export default class Module {
 
 			statement = name === 'default' ? this.exports.default.statement : this.definitions[ name ];
 			promise = statement && !statement.isIncluded ? statement.mark() : emptyArrayPromise;
-
-			// Special case - `export default foo; foo += 1` - need to be
-			// vigilant about maintaining the correct order of the export
-			// declaration. Otherwise, the export declaration will always
-			// go at the end of the expansion, because the expansion of
-			// `foo` will include statements *after* the declaration
-			if ( name === 'default' && this.exports.default.identifier && this.exports.default.isModified ) {
-				const defaultExportStatement = this.exports.default.statement;
-				promise = promise.then( statements => {
-					// remove the default export statement...
-					// TODO could this be statements.pop()?
-					statements.splice( statements.indexOf( defaultExportStatement ), 1 );
-
-					let i = statements.length;
-					let inserted = false;
-
-					while ( i-- ) {
-						if ( statements[i].module === this && statements[i].index < defaultExportStatement.index ) {
-							statements.splice( i + 1, 0, defaultExportStatement );
-							inserted = true;
-							break;
-						}
-					}
-
-					if ( !inserted ) statements.push( statement );
-					return statements;
-				});
-			}
 		}
 
 		this.definitionPromises[ name ] = promise || emptyArrayPromise;