Move ExecProgram to interpreter/ (#802)

Seems to make sense since it's the only interpreter/ dependency in syntax/ right now, so this feels like untangling deps.

Fixes #371

executable_semantics/interpreter/BUILD

@@ -2,7 +2,7 @@
 # Exceptions. See /LICENSE for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-package(default_visibility = ["//executable_semantics:__subpackages__"])
+package(default_visibility = ["//executable_semantics:__pkg__"])
 
 cc_library(
     name = "action",
@@ -36,6 +36,16 @@ cc_library(
     deps = ["//executable_semantics/common:arena"],
 )
 
+cc_library(
+    name = "exec_program",
+    srcs = ["exec_program.cpp"],
+    hdrs = ["exec_program.h"],
+    deps = [
+        ":interpreter",
+        ":type_checker",
+    ],
+)
+
 cc_library(
     name = "field_path",
     hdrs = ["field_path.h"],

executable_semantics/interpreter/exec_program.cpp

@@ -0,0 +1,69 @@
+// 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
+
+#include "executable_semantics/interpreter/exec_program.h"
+
+#include "common/check.h"
+#include "common/ostream.h"
+#include "executable_semantics/common/arena.h"
+#include "executable_semantics/common/tracing_flag.h"
+#include "executable_semantics/interpreter/interpreter.h"
+#include "executable_semantics/interpreter/type_checker.h"
+
+namespace Carbon {
+
+// Adds builtins, currently only Print(). Note Print() is experimental, not
+// standardized, but is made available for printing state in tests.
+static void AddIntrinsics(std::list<Ptr<const Declaration>>* fs) {
+  SourceLocation loc("<intrinsic>", 0);
+  std::vector<TuplePattern::Field> print_fields = {TuplePattern::Field(
+      "0", global_arena->New<BindingPattern>(
+               loc, "format_str",
+               global_arena->New<ExpressionPattern>(
+                   global_arena->New<StringTypeLiteral>(loc))))};
+  auto print_return =
+      global_arena->New<Return>(loc,
+                                global_arena->New<IntrinsicExpression>(
+                                    IntrinsicExpression::IntrinsicKind::Print),
+                                false);
+  auto print = global_arena->New<FunctionDeclaration>(
+      global_arena->New<FunctionDefinition>(
+          loc, "Print", std::vector<GenericBinding>(),
+          global_arena->New<TuplePattern>(loc, print_fields),
+          global_arena->New<ExpressionPattern>(
+              global_arena->New<TupleLiteral>(loc)),
+          /*is_omitted_return_type=*/false, print_return));
+  fs->insert(fs->begin(), print);
+}
+
+void ExecProgram(std::list<Ptr<const Declaration>> fs) {
+  AddIntrinsics(&fs);
+  if (tracing_output) {
+    llvm::outs() << "********** source program **********\n";
+    for (const auto decl : fs) {
+      llvm::outs() << *decl;
+    }
+    llvm::outs() << "********** type checking **********\n";
+  }
+  TypeChecker type_checker;
+  TypeChecker::TypeCheckContext p = type_checker.TopLevel(fs);
+  TypeEnv top = p.types;
+  Env ct_top = p.values;
+  std::list<Ptr<const Declaration>> new_decls;
+  for (const auto decl : fs) {
+    new_decls.push_back(type_checker.MakeTypeChecked(decl, top, ct_top));
+  }
+  if (tracing_output) {
+    llvm::outs() << "\n";
+    llvm::outs() << "********** type checking complete **********\n";
+    for (const auto decl : new_decls) {
+      llvm::outs() << *decl;
+    }
+    llvm::outs() << "********** starting execution **********\n";
+  }
+  int result = Interpreter().InterpProgram(new_decls);
+  llvm::outs() << "result: " << result << "\n";
+}
+
+}  // namespace Carbon

executable_semantics/interpreter/exec_program.h

@@ -0,0 +1,24 @@
+// 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
+
+// Helpers should be added here when logic in syntax.ypp is more than a single
+// statement. The intent is to minimize the amount of C++ in the .ypp file, to
+// improve ease of maintenance.
+
+#ifndef EXECUTABLE_SEMANTICS_INTERPRETER_EXEC_PROGRAM_H_
+#define EXECUTABLE_SEMANTICS_INTERPRETER_EXEC_PROGRAM_H_
+
+#include <list>
+
+#include "executable_semantics/ast/declaration.h"
+#include "executable_semantics/common/ptr.h"
+
+namespace Carbon {
+
+// Runs the top-level declaration list.
+void ExecProgram(std::list<Ptr<const Declaration>> fs);
+
+}  // namespace Carbon
+
+#endif  // EXECUTABLE_SEMANTICS_INTERPRETER_EXEC_PROGRAM_H_