libexpr: pass Exprs as references, not pointers

almost all places where Exprs are passed as pointers expect the pointers
to be non-null. pass them as references to encode this constraint in the
type system as well (and also communicate that Exprs must not be freed).

Change-Id: Ia98f166fec3c23151f906e13acb4a0954a5980a2

1 files changed, 10 insertions, 10 deletions

diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 24ab8acb9..99abbe44b 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -155,7 +155,7 @@ struct NixRepl
     void reloadFiles();
     void addAttrsToScope(Value & attrs);
     void addVarToScope(const Symbol name, Value & v);
-    Expr * parseString(std::string s);
+    Expr & parseString(std::string s);
     void evalString(std::string s, Value & v);
     void loadDebugTraceEnv(DebugTrace & dt);
 
@@ -428,9 +428,9 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
             auto expr = cur.substr(0, dot);
             auto cur2 = cur.substr(dot + 1);
 
-            Expr * e = parseString(expr);
+            Expr & e = parseString(expr);
             Value v;
-            e->eval(*state, *env, v);
+            e.eval(*state, *env, v);
             state->forceAttrs(v, noPos, "while evaluating an attrset for the purpose of completion (this error should not be displayed; file an issue?)");
 
             for (auto & i : *v.attrs) {
@@ -821,7 +821,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
             line[p + 1] != '=' &&
             isVarName(name = removeWhitespace(line.substr(0, p))))
         {
-            Expr * e = parseString(line.substr(p + 1));
+            Expr & e = parseString(line.substr(p + 1));
             Value & v(*state->allocValue());
             v.mkThunk(env, e);
             addVarToScope(state->symbols.create(name), v);
@@ -946,7 +946,7 @@ Value * NixRepl::getReplOverlaysEvalFunction()
     auto code =
         #include "repl-overlays.nix.gen.hh"
         ;
-    auto expr = state->parseExprFromString(
+    auto & expr = state->parseExprFromString(
         code,
         SourcePath(evalReplInitFilesPath),
         state->staticBaseEnv
@@ -1054,7 +1054,7 @@ Value * NixRepl::bindingsToAttrs()
 }
 
 
-Expr * NixRepl::parseString(std::string s)
+Expr & NixRepl::parseString(std::string s)
 {
     return state->parseExprFromString(std::move(s), state->rootPath(CanonPath::fromCwd()), staticEnv);
 }
@@ -1062,16 +1062,16 @@ Expr * NixRepl::parseString(std::string s)
 
 void NixRepl::evalString(std::string s, Value & v)
 {
-    Expr * e = parseString(s);
-    e->eval(*state, *env, v);
+    Expr & e = parseString(s);
+    e.eval(*state, *env, v);
     state->forceValue(v, v.determinePos(noPos));
 }
 
 Value * NixRepl::evalFile(SourcePath & path)
 {
-    auto expr = state->parseExprFromFile(path, staticEnv);
+    auto & expr = state->parseExprFromFile(path, staticEnv);
     Value * result(state->allocValue());
-    expr->eval(*state, *env, *result);
+    expr.eval(*state, *env, *result);
     state->forceValue(*result, result->determinePos(noPos));
     return result;
 }