Merge pull request #9370 from hercules-ci/add-value-types

refactor: Add `Value` types, use `std::span` for list iteration

src/libexpr/value.hh

@@ -3,6 +3,7 @@
 
 #include <cassert>
 #include <climits>
+#include <span>
 
 #include "symbol-table.hh"
 #include "value/context.hh"
@@ -158,64 +159,72 @@ public:
  inline bool isPrimOp() const { return internalType == tPrimOp; };
  inline bool isPrimOpApp() const { return internalType == tPrimOpApp; };
 
- union
- {
- NixInt integer;
- bool boolean;
+ /**
+ * Strings in the evaluator carry a so-called `context` which
+ * is a list of strings representing store paths. This is to
+ * allow users to write things like
+ *
+ * "--with-freetype2-library=" + freetype + "/lib"
+ *
+ * where `freetype` is a derivation (or a source to be copied
+ * to the store). If we just concatenated the strings without
+ * keeping track of the referenced store paths, then if the
+ * string is used as a derivation attribute, the derivation
+ * will not have the correct dependencies in its inputDrvs and
+ * inputSrcs.
+
+ * The semantics of the context is as follows: when a string
+ * with context C is used as a derivation attribute, then the
+ * derivations in C will be added to the inputDrvs of the
+ * derivation, and the other store paths in C will be added to
+ * the inputSrcs of the derivations.
+
+ * For canonicity, the store paths should be in sorted order.
+ */
+ struct StringWithContext {
+ const char * c_str;
+ const char * * context; // must be in sorted order
+ };
 
-  /**
- * Strings in the evaluator carry a so-called `context` which
-  * is a list of strings representing store paths. This is to
-  * allow users to write things like
+ struct Path {
+ InputAccessor * accessor;
+ const char * path;
+ };
 
- * "--with-freetype2-library=" + freetype + "/lib"
+ struct ClosureThunk {
+ Env * env;
+ Expr * expr;
+ };
 
- * where `freetype` is a derivation (or a source to be copied
- * to the store). If we just concatenated the strings without
- * keeping track of the referenced store paths, then if the
- * string is used as a derivation attribute, the derivation
- * will not have the correct dependencies in its inputDrvs and
- * inputSrcs.
+ struct FunctionApplicationThunk {
+ Value * left, * right;
+ };
 
- * The semantics of the context is as follows: when a string
- * with context C is used as a derivation attribute, then the
- * derivations in C will be added to the inputDrvs of the
- * derivation, and the other store paths in C will be added to
- * the inputSrcs of the derivations.
+ struct Lambda {
+ Env * env;
+ ExprLambda * fun;
+ };
 
- * For canonicity, the store paths should be in sorted order.
- */
- struct {
- const char * c_str;
- const char * * context; // must be in sorted order
- } string;
+ union
+ {
+ NixInt integer;
+ bool boolean;
 
- struct {
- InputAccessor * accessor;
- const char * path;
- } _path;
+ StringWithContext string;
+
+ Path _path;
 
  Bindings * attrs;
  struct {
  size_t size;
  Value * * elems;
  } bigList;
  Value * smallList[2];
- struct {
- Env * env;
- Expr * expr;
- } thunk;
- struct {
- Value * left, * right;
- } app;
- struct {
- Env * env;
- ExprLambda * fun;
- } lambda;
+ ClosureThunk thunk;
+ FunctionApplicationThunk app;
+ Lambda lambda;
  PrimOp * primOp;
- struct {
- Value * left, * right;
- } primOpApp;
+ FunctionApplicationThunk primOpApp;
  ExternalValueBase * external;
  NixFloat fpoint;
  };
@@ -387,7 +396,13 @@ public:
  return internalType == tList1 || internalType == tList2 ? smallList : bigList.elems;
  }
 
- const Value * const * listElems() const
+ std::span<Value * const> listItems() const
+ {
+ assert(isList());
+ return std::span<Value * const>(listElems(), listSize());
+ }
+
+ Value * const * listElems() const
  {
  return internalType == tList1 || internalType == tList2 ? smallList : bigList.elems;
  }
@@ -406,34 +421,6 @@ public:
  */
  bool isTrivial() const;
 
- auto listItems()
- {
- struct ListIterable
- {
- typedef Value * const * iterator;
- iterator _begin, _end;
- iterator begin() const { return _begin; }
- iterator end() const { return _end; }
- };
- assert(isList());
- auto begin = listElems();
- return ListIterable { begin, begin + listSize() };
- }
-
- auto listItems() const
- {
- struct ConstListIterable
- {
- typedef const Value * const * iterator;
- iterator _begin, _end;
- iterator begin() const { return _begin; }
- iterator end() const { return _end; }
- };
- assert(isList());
- auto begin = listElems();
- return ConstListIterable { begin, begin + listSize() };
- }
-
  SourcePath path() const
  {
  assert(internalType == tPath);

src/nix-env/nix-env.cc

@@ -172,7 +172,7 @@ static void loadSourceExpr(EvalState & state, const SourcePath & path, Value & v
  directory). */
  else if (st.type == InputAccessor::tDirectory) {
  auto attrs = state.buildBindings(maxAttrs);
- attrs.alloc("_combineChannels").mkList(0);
+ state.mkList(attrs.alloc("_combineChannels"), 0);
  StringSet seen;
  getAllExprs(state, path, seen, attrs);
  v.mkAttrs(attrs);