handle pathological cycles

src/Bundle.js

@@ -68,7 +68,10 @@ export default class Bundle {
 				entryModule.getExports().forEach( name => {
 					const declaration = entryModule.traceExport( name );
 					declaration.isExported = true;
-					declaration.statement.mark();
+
+					if ( declaration.statement ) {
+						declaration.statement.mark();
+					}
 				});
 
 				this.markAllModifierStatements();

src/Module.js

@@ -254,9 +254,19 @@ export default class Module {
 
 		this.statements.forEach( statement => {
 			statement.references.forEach( reference => {
-				if ( reference.declaration && reference.declaration.statement ) {
-					const module = reference.declaration.statement.module;
+				const declaration = reference.declaration;
+
+				if ( declaration && declaration.statement ) {
+					const module = declaration.statement.module;
+					if ( module === this ) return;
+
 					weakDependencies[ module.id ] = module;
+
+					// TODO handle references inside IIFEs, and disregard
+					// function declarations
+					if ( !reference.scope.parent ) {
+						strongDependencies[ module.id ] = module;
+					}
 				}
 			});
 		});