Enforce strict field initialization (#1349)

BREAKING CHANGE: Instance fields not definitely assigned within the constructor now yield an error, unless the field's name is annotated with a trailing `!` (checked at runtime), is of a nullable or is of a value type (initialized to zero). Fields of non-nullable reference types must be assigned before `this` is either implicitly or explicitly returned from the constructor, passed to another function or another instance method is called on `this`. Overall the behavior is similar to, but not exactly the same as `--strictPropertyInitialization` in TypeScript.

Author: dcodeIO

src/ast.ts

@@ -748,15 +748,27 @@ export abstract class Node {
     return false;
   }
 
-  /** Checks if this is a call calling a method on super. */
-  get isCallOnSuper(): bool {
-    if (this.kind != NodeKind.CALL) return false;
-    var expression = changetype<CallExpression>(this).expression;
-    if (expression.kind != NodeKind.PROPERTYACCESS) return false;
-    var target = (<PropertyAccessExpression>expression).expression;
-    if (target.kind == NodeKind.SUPER) return true;
+  private isAccessOn(kind: NodeKind): bool {
+    let node = changetype<Node>(this);
+    if (node.kind == NodeKind.CALL) {
+      node = (<CallExpression>node).expression;
+    }
+    if (node.kind == NodeKind.PROPERTYACCESS) {
+      let target = (<PropertyAccessExpression>node).expression;
+      if (target.kind == kind) return true;
+    }
     return false;
   }
+
+  /** Checks if this node accesses a method or property on `this`. */
+  get isAccessOnThis(): bool {
+    return this.isAccessOn(NodeKind.THIS);
+  }
+
+  /** Checks if this node accesses a method or property on `super`. */
+  get isAccessOnSuper(): bool {
+    return this.isAccessOn(NodeKind.SUPER);
+  }
 }
 
 // types
@@ -1518,12 +1530,12 @@ export class Source extends Node {
     /** Full source text. */
     public text: string
   ) {
-    super(NodeKind.SOURCE, changetype<Range>(0)); // ¯\(ツ)/¯
-    this.range = new Range(this, 0, text.length);
+    super(NodeKind.SOURCE, new Range(0, text.length));
     var internalPath = mangleInternalPath(normalizedPath);
     this.internalPath = internalPath;
     var pos = internalPath.lastIndexOf(PATH_DELIMITER);
     this.simplePath = pos >= 0 ? internalPath.substring(pos + 1) : internalPath;
+    this.range.source = this;
   }
 
   /** Path used internally. */

src/builtins.ts

@@ -2894,7 +2894,9 @@ function builtin_instantiate(ctx: BuiltinContext): ExpressionRef {
     return module.unreachable();
   }
   compiler.currentType = classInstance.type;
-  return compiler.compileInstantiate(classInstance, operands, Constraints.NONE, ctx.reportNode);
+  var ctor = compiler.ensureConstructor(classInstance, ctx.reportNode);
+  compiler.checkFieldInitialization(classInstance, ctx.reportNode);
+  return compiler.compileInstantiate(ctor, operands, Constraints.NONE, ctx.reportNode);
 }
 builtins.set(BuiltinNames.instantiate, builtin_instantiate);
 

src/common.ts

@@ -37,7 +37,7 @@ export enum CommonFlags {
   /** Has a `set` modifier. */
   SET = 1 << 12,
   /** Has a definite assignment assertion `!` as in `x!: i32;`. */
-  DEFINITE_ASSIGNMENT = 1 << 13,
+  DEFINITELY_ASSIGNED = 1 << 13,
 
   // Extended modifiers usually derived from basic modifiers