[Decompiler] Replace type hint system and improve variable types. (#320)

* get gkernel and gkernel-h at least somewhat working in the offline tests

* strip comments from json

* switch hints to casts. online tests passing, offline passing up to gkernel

* variable retyping is added

* fix up casts in lets

* update

common/util/json_util.cpp

@@ -0,0 +1,100 @@
+#include <cassert>
+#include "json_util.h"
+
+/*!
+ * Strip out // and / * comments
+ * Does not strip comments from within a string.
+ * Assumes \" is used to escape quotes inside of a string.
+ */
+std::string strip_cpp_style_comments(const std::string& input) {
+  std::string output;
+
+  enum State { NORMAL, BLOCK_COMMENT, LINE_COMMENT, STRING } state = NORMAL;
+
+  for (size_t i = 0; i < input.size(); i++) {
+    char c = input[i];
+    char next = i < (input.size() - 1) ? input[i + 1] : '\0';
+    char prev = i > 0 ? input[i - 1] : '\0';
+
+    switch (state) {
+      case NORMAL:
+        if (c == '/' && next == '*') {
+          // Normal -> block
+          state = BLOCK_COMMENT;
+          i++;  // skip over *
+        } else if (c == '/' && next == '/') {
+          // Normal -> line
+          state = LINE_COMMENT;
+          i++;
+        } else if (c == '"') {
+          // Normal -> string
+          state = STRING;
+          output.push_back(c);
+        } else {
+          // Normal -> normal
+          output.push_back(c);
+        }
+        break;
+      case BLOCK_COMMENT:
+        if (c == '*' && next == '/') {
+          // Block -> normal
+          state = NORMAL;
+          i++;
+        }
+        // otherwise stay in block comment
+        break;
+      case LINE_COMMENT:
+        if (c == '\n') {
+          state = NORMAL;
+          output.push_back(c);
+        }
+        break;
+      case STRING:
+        if (c == '"' && prev != '\\') {
+          state = NORMAL;
+        }
+        output.push_back(c);
+        break;
+      default:
+        assert(false);
+    }
+  }
+
+  if (state == BLOCK_COMMENT) {
+    throw std::runtime_error("strip_cpp_style_comments ended in a block comment");
+  }
+
+  if (state == STRING) {
+    throw std::runtime_error("strip_cpp_style_comments ended in a string.");
+  }
+
+  return output;
+}
+
+/*!
+ * Parse JSON file with comments stripped. Unlike the default comment stripping feature
+ * of nlohmann::json, this allows you to have multiple comments in a row!
+ */
+nlohmann::json parse_commented_json(const std::string& input) {
+  return nlohmann::json::parse(strip_cpp_style_comments(input));
+}
+
+/*!
+ * Parse something like:
+ * 2 -> Range(2, 3)
+ * [2, 3] -> Range(2, 3)
+ * [2, 10] -> Range(2, 10)
+ */
+Range<int> parse_json_optional_integer_range(const nlohmann::json& json) {
+  if (json.is_number_integer()) {
+    auto first = json.get<int>();
+    return Range<int>(first, first + 1);
+  } else if (json.is_array()) {
+    if (json.size() != 2) {
+      throw std::runtime_error("Invalid array size in parse_json_optional_integer_range");
+    }
+    return {json[0].get<int>(), json[1].get<int>()};
+  } else {
+    throw std::runtime_error("Invalid json as input to parse_json_optional_integer_range");
+  }
+}