Support for if ... then ... else following #911. (#944)

executable_semantics/testdata/if_expression/if_then_else.carbon

@@ -0,0 +1,21 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// RUN: %{executable_semantics} %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes=false %s
+// RUN: %{executable_semantics} --trace %s 2>&1 | \
+// RUN:   %{FileCheck} --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: %{executable_semantics} %s
+// CHECK: result: 12
+
+package ExecutableSemanticsTest api;
+
+fn Main() -> i32 {
+  var cond: if true then Bool else i32 = true;
+  if (if cond then true else false) {}
+  while (if cond then false else true) {}
+  return if if cond then true or false else false and true
+         then if not cond then 1 + 2 else 3 * 4
+         else if not cond then 5 + 6 else 7 * 8;
+}