Merge commit '6e92d2345e8231a44556ce7d416451f5f3e6c398' as 'engine262'

engine262/src/runtime-semantics/IfStatement.mts

@@ -0,0 +1,49 @@
+import { Evaluate } from '../evaluator.mts';
+import {
+  Completion,
+  EnsureCompletion,
+  NormalCompletion,
+  Q,
+  UpdateEmpty,
+} from '../completion.mts';
+import { Value } from '../value.mts';
+import type { ParseNode } from '../parser/ParseNode.mts';
+import {
+  GetValue,
+  ToBoolean,
+} from '#self';
+
+/** https://tc39.es/ecma262/#sec-if-statement-runtime-semantics-evaluation */
+// IfStatement :
+//   `if` `(` Expression `)` Statement `else` Statement
+//   `if` `(` Expression `)` Statement
+export function* Evaluate_IfStatement({ Expression, Statement_a, Statement_b }: ParseNode.IfStatement) {
+  // 1. Let exprRef be the result of evaluating Expression.
+  const exprRef = Q(yield* Evaluate(Expression));
+  // 2. Let exprValue be ! ToBoolean(? GetValue(exprRef)).
+  const exprValue = ToBoolean(Q(yield* GetValue(exprRef)));
+  if (Statement_b) {
+    let stmtCompletion;
+    // 3. If exprValue is true, then
+    if (exprValue === Value.true) {
+      // a. Let stmtCompletion be the result of evaluating the first Statement.
+      stmtCompletion = yield* Evaluate(Statement_a);
+    } else { // 4. Else,
+      // a. Let stmtCompletion be the result of evaluating the second Statement.
+      stmtCompletion = yield* Evaluate(Statement_b);
+    }
+    // 5. Return Completion(UpdateEmpty(stmtCompletion, undefined)).
+    return Completion(UpdateEmpty(EnsureCompletion(stmtCompletion), Value.undefined));
+  } else {
+    // 3. If exprValue is false, then
+    if (exprValue === Value.false) {
+      // a. Return NormalCompletion(undefined).
+      return NormalCompletion(Value.undefined);
+    } else { // 4. Else,
+      // a. Let stmtCompletion be the result of evaluating Statement.
+      const stmtCompletion = yield* Evaluate(Statement_a);
+      // b. Return Completion(UpdateEmpty(stmtCompletion, undefined)).
+      return Completion(UpdateEmpty(EnsureCompletion(stmtCompletion), Value.undefined));
+    }
+  }
+}