Put preceding statements for class fields in the constructor instead of file scope (#1209)

Perryvw · web-flow · commit 61bfff3eea55 · 2022-01-13T22:01:28.000+01:00
diff --git a/src/transformation/visitors/class/members/constructor.ts b/src/transformation/visitors/class/members/constructor.ts
@@ -2,6 +2,7 @@ import * as ts from "typescript";
 import * as lua from "../../../../LuaAST";
 import { TransformationContext } from "../../../context";
 import { createSelfIdentifier } from "../../../utils/lua-ast";
+import { transformInPrecedingStatementScope } from "../../../utils/preceding-statements";
 import { popScope, pushScope, ScopeType } from "../../../utils/scope";
 import { transformFunctionBodyContent, transformFunctionBodyHeader, transformParameters } from "../../function";
 import { transformIdentifier } from "../../identifier";
@@ -43,7 +44,9 @@ export function transformConstructorDeclaration(
     // Check for field declarations in constructor
     const constructorFieldsDeclarations = statement.parameters.filter(p => p.modifiers !== undefined);
 
-    const classInstanceFields = transformClassInstanceFields(context, instanceFields);
+    const [fieldsPrecedingStatements, classInstanceFields] = transformInPrecedingStatementScope(context, () =>
+        transformClassInstanceFields(context, instanceFields)
+    );
 
     // If there are field initializers and the first statement is a super call,
     // move super call between default assignments and initializers
@@ -78,6 +81,7 @@ export function transformConstructorDeclaration(
         // else { TypeScript error: A parameter property may not be declared using a binding pattern }
     }
 
+    bodyWithFieldInitializers.push(...fieldsPrecedingStatements);
     bodyWithFieldInitializers.push(...classInstanceFields);
 
     bodyWithFieldInitializers.push(...body);
diff --git a/test/unit/precedingStatements.spec.ts b/test/unit/precedingStatements.spec.ts
@@ -623,3 +623,15 @@ test("else if", () => {
         return i;
     `.expectToMatchJsResult();
 });
+
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1208
+test("class member initializers", () => {
+    util.testFunction`
+        class MyClass {
+            myField = false ?? true;
+            constructor(public foo: number = 0 ?? 5) {}
+        }
+        const inst = new MyClass();
+        return [inst.myField, inst.foo];
+    `.expectToMatchJsResult();
+});
