diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 20a586f60..4a81eaa47 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -233,7 +233,7 @@ struct ExprSelect : Expr
     PosIdx pos;
     Expr * e, * def;
     AttrPath attrPath;
-    ExprSelect(const PosIdx & pos, Expr * e, const AttrPath & attrPath, Expr * def) : pos(pos), e(e), def(def), attrPath(attrPath) { };
+    ExprSelect(const PosIdx & pos, Expr * e, const AttrPath && attrPath, Expr * def) : pos(pos), e(e), def(def), attrPath(std::move(attrPath)) { };
     ExprSelect(const PosIdx & pos, Expr * e, Symbol name) : pos(pos), e(e), def(0) { attrPath.push_back(AttrName(name)); };
     PosIdx getPos() const override { return pos; }
     COMMON_METHODS
@@ -243,7 +243,7 @@ struct ExprOpHasAttr : Expr
 {
     Expr * e;
     AttrPath attrPath;
-    ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
+    ExprOpHasAttr(Expr * e, const AttrPath && attrPath) : e(e), attrPath(std::move(attrPath)) { };
     PosIdx getPos() const override { return e->getPos(); }
     COMMON_METHODS
 };
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 1dd4a801f..dec5818fc 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -90,7 +90,7 @@ static void dupAttr(const EvalState & state, Symbol attr, const PosIdx pos, cons
 }
 
 
-static void addAttr(ExprAttrs * attrs, AttrPath & attrPath,
+static void addAttr(ExprAttrs * attrs, AttrPath && attrPath,
     Expr * e, const PosIdx pos, const nix::EvalState & state)
 {
     AttrPath::iterator i;
@@ -188,7 +188,7 @@ static Formals * toFormals(ParseData & data, ParserFormals * formals,
 
 
 static Expr * stripIndentation(const PosIdx pos, SymbolTable & symbols,
-    std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken>>> & es)
+    std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken>>> && es)
 {
     if (es.empty()) return new ExprString("");
 
@@ -408,7 +408,7 @@ expr_op
   | expr_op OR expr_op { $$ = new ExprOpOr(makeCurPos(@2, data), $1, $3); }
   | expr_op IMPL expr_op { $$ = new ExprOpImpl(makeCurPos(@2, data), $1, $3); }
   | expr_op UPDATE expr_op { $$ = new ExprOpUpdate(makeCurPos(@2, data), $1, $3); }
-  | expr_op '?' attrpath { $$ = new ExprOpHasAttr($1, *$3); }
+  | expr_op '?' attrpath { $$ = new ExprOpHasAttr($1, std::move(*$3)); delete $3; }
   | expr_op '+' expr_op
     { $$ = new ExprConcatStrings(makeCurPos(@2, data), false, new std::vector<std::pair<PosIdx, Expr *> >({{makeCurPos(@1, data), $1}, {makeCurPos(@3, data), $3}})); }
   | expr_op '-' expr_op { $$ = new ExprCall(makeCurPos(@2, data), new ExprVar(data->symbols.create("__sub")), {$1, $3}); }
@@ -431,9 +431,9 @@ expr_app
 
 expr_select
   : expr_simple '.' attrpath
-    { $$ = new ExprSelect(CUR_POS, $1, *$3, 0); }
+    { $$ = new ExprSelect(CUR_POS, $1, std::move(*$3), nullptr); delete $3; }
   | expr_simple '.' attrpath OR_KW expr_select
-    { $$ = new ExprSelect(CUR_POS, $1, *$3, $5); }
+    { $$ = new ExprSelect(CUR_POS, $1, std::move(*$3), $5); delete $3; }
   | /* Backwards compatibility: because Nixpkgs has a rarely used
        function named ‘or’, allow stuff like ‘map or [...]’. */
     expr_simple OR_KW
@@ -453,7 +453,8 @@ expr_simple
   | FLOAT { $$ = new ExprFloat($1); }
   | '"' string_parts '"' { $$ = $2; }
   | IND_STRING_OPEN ind_string_parts IND_STRING_CLOSE {
-      $$ = stripIndentation(CUR_POS, data->symbols, *$2);
+      $$ = stripIndentation(CUR_POS, data->symbols, std::move(*$2));
+      delete $2;
   }
   | path_start PATH_END
   | path_start string_parts_interpolated PATH_END {
@@ -533,7 +534,7 @@ ind_string_parts
   ;
 
 binds
-  : binds attrpath '=' expr ';' { $$ = $1; addAttr($$, *$2, $4, makeCurPos(@2, data), data->state); }
+  : binds attrpath '=' expr ';' { $$ = $1; addAttr($$, std::move(*$2), $4, makeCurPos(@2, data), data->state); delete $2; }
   | binds INHERIT attrs ';'
     { $$ = $1;
       for (auto & i : *$3) {
@@ -542,6 +543,7 @@ binds
           auto pos = makeCurPos(@3, data);
           $$->attrs.emplace(i.symbol, ExprAttrs::AttrDef(new ExprVar(CUR_POS, i.symbol), pos, true));
       }
+      delete $3;
     }
   | binds INHERIT '(' expr ')' attrs ';'
     { $$ = $1;
@@ -551,6 +553,7 @@ binds
               dupAttr(data->state, i.symbol, makeCurPos(@6, data), $$->attrs[i.symbol].pos);
           $$->attrs.emplace(i.symbol, ExprAttrs::AttrDef(new ExprSelect(CUR_POS, $4, i.symbol), makeCurPos(@6, data)));
       }
+      delete $6;
     }
   | { $$ = new ExprAttrs(makeCurPos(@0, data)); }
   ;
@@ -612,9 +615,9 @@ expr_list
 
 formals
   : formal ',' formals
-    { $$ = $3; $$->formals.push_back(*$1); }
+    { $$ = $3; $$->formals.emplace_back(*$1); delete $1; }
   | formal
-    { $$ = new ParserFormals; $$->formals.push_back(*$1); $$->ellipsis = false; }
+    { $$ = new ParserFormals; $$->formals.emplace_back(*$1); $$->ellipsis = false; delete $1; }
   |
     { $$ = new ParserFormals; $$->ellipsis = false; }
   | ELLIPSIS