chore: split creating a new Signature into separate methods when having

a single vs multiple return types

Author: JairusSW

src/compiler.ts

@@ -6800,7 +6800,7 @@ export class Compiler extends DiagnosticEmitter {
     let usizeType = this.options.usizeType;
     let sizeTypeRef = usizeType.toRef();
     let parameterTypes = instance.signature.parameterTypes;
-    let returnType = instance.signature.returnType;
+    let resultRefs = instance.signature.resultRefs;
     let hasReturnValue = instance.signature.numReturnTypes > 0;
     let numParameters = parameterTypes.length;
     let tempIndex = 1 + parameterTypes.length; // incl. `this`
@@ -6904,7 +6904,7 @@ export class Compiler extends DiagnosticEmitter {
     let body: ExpressionRef;
     let instanceClass = instance.getBoundClassOrInterface();
     if (!instance.is(CommonFlags.Abstract) && !(instanceClass && instanceClass.kind == ElementKind.Interface)) {
-      let paramExprs = new Array<ExpressionRef>(numParameters);
+      let paramExprs = new Array<ExpressionRef>(numParameters + 1);
       paramExprs[0] = module.local_get(0, sizeTypeRef); // this
       for (let i = 0, k = parameterTypes.length; i < k; ++i) {
         paramExprs[1 + i] = module.local_get(1 + i, parameterTypes[i].toRef());
@@ -6927,7 +6927,7 @@ export class Compiler extends DiagnosticEmitter {
       module.block(null, [
         builder.render(tempIndex),
         body
-      ], resultRefs)
+      ], stub.signature.resultRefs)
     );
     stub.set(CommonFlags.Compiled);
   }