Switch executable semantics to use ErrorBuilder directly and relocate macros (#1184)

executable_semantics/common/error_builders.h

@@ -0,0 +1,44 @@
+// 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
+
+#ifndef EXECUTABLE_SEMANTICS_COMMON_ERROR_BUILDERS_H_
+#define EXECUTABLE_SEMANTICS_COMMON_ERROR_BUILDERS_H_
+
+#include "common/error.h"
+#include "executable_semantics/common/source_location.h"
+
+namespace Carbon {
+
+// Builds an Error instance with the specified message. This should be used for
+// non-recoverable errors with user input.
+//
+// For example:
+//   return ProgramError(line_num) << "Line is bad!";
+//   return ProgramError() << "Application is bad!";
+//
+// Where possible, try to identify the error as a compilation or runtime error.
+// Use CHECK/FATAL for internal errors. The generic program error option is
+// provided as a fallback for cases that don't fit those classifications.
+
+inline auto CompilationError(SourceLocation loc) -> ErrorBuilder {
+  ErrorBuilder builder;
+  (void)(builder << "COMPILATION ERROR: " << loc << ": ");
+  return builder;
+}
+
+inline auto ProgramError(SourceLocation loc) -> ErrorBuilder {
+  ErrorBuilder builder;
+  (void)(builder << "PROGRAM ERROR: " << loc << ": ");
+  return builder;
+}
+
+inline auto RuntimeError(SourceLocation loc) -> ErrorBuilder {
+  ErrorBuilder builder;
+  (void)(builder << "RUNTIME ERROR: " << loc << ": ");
+  return builder;
+}
+
+}  // namespace Carbon
+
+#endif  // EXECUTABLE_SEMANTICS_COMMON_ERROR_BUILDERS_H_