Bind the standard library to a $std variable and use it in desugared expressions. (#1158)

This keeps redefining `std` from breaking expressions that desugar to calls to standard library functions by redefining `std`.

Author: eduardosm

core/desugarer.cpp

@@ -100,6 +100,7 @@ static constexpr char STD_CODE[] = {
  */
 class Desugarer {
     Allocator *alloc;
+    bool isStdlib;
 
     template <class T, class... Args>
     T *make(Args &&... args)
@@ -139,7 +140,10 @@ class Desugarer {
 
     Var *std(void)
     {
-        return var(id(U"std"));
+        // In most places, there is a "$std" variable inserted by
+        // the desugarer. On the standard library itself there isn't,
+        // so use "std" instead.
+        return var(id(isStdlib ? U"std" : U"$std"));
     }
 
     Local::Bind bind(const Identifier *id, AST *body)
@@ -219,7 +223,7 @@ class Desugarer {
     }
 
    public:
-    Desugarer(Allocator *alloc) : alloc(alloc) {}
+    Desugarer(Allocator *alloc, bool isStdlib = false) : alloc(alloc), isStdlib(isStdlib) {}
 
     void desugarParams(ArgParams &params, unsigned obj_level)
     {
@@ -999,13 +1003,17 @@ class Desugarer {
                                               make<Var>(E, line_end, body)));
         }
 
-        // local std = (std.jsonnet stuff); ast
-        ast = make<Local>(ast->location, EF, singleBind(id(U"std"), std_obj), ast);
+        // local $std = (std.jsonnet stuff); std = $std; ast
+        // The standard library is bound to $std, which cannot be overriden,
+        // so redefining std won't break expressions that desugar to calls
+        // to standard library functions.
+        ast = make<Local>(ast->location, EF, singleBind(id(U"std"), std()), ast);
+        ast = make<Local>(ast->location, EF, singleBind(id(U"$std"), std_obj), ast);
     }
 };
 
 DesugaredObject *makeStdlibAST(Allocator *alloc, std::string filename) {
-    Desugarer desugarer(alloc);
+    Desugarer desugarer(alloc, true);
     return desugarer.stdlibAST(filename);
 }
 

doc/ref/spec.html

@@ -1125,7 +1125,7 @@ <h3 id="desugaring">Desugaring</h3>
         </p>
         <div class="desugar-rule">
           \[
-            desugar(e) =  desugar_{expr}(\local{\texttt{std} = e_{std}}{e}, false)
+            desugar(e) =  desugar_{expr}(\local{\texttt{\$std} = e_{std}}{\local{\texttt{std} = \texttt{\$std}}{e}}, false)
           \]
         </div>
       </div>
@@ -1287,7 +1287,7 @@ <h3 id="desugaring">Desugaring</h3>
         <div class="desugar-rule">
           \[
             desugar_{expr}(e[e':e'':e'''], b) =
-                desugar_{expr}(\texttt{std.slice}(e, e', e'', e'''), b)
+                desugar_{expr}(\texttt{\$std.slice}(e, e', e'', e'''), b)
           \]
         </div>
 
@@ -1318,27 +1318,27 @@ <h3 id="desugaring">Desugaring</h3>
 
         <div class="desugar-rule">
           \[
-            desugar_{expr}(e \mathop{==} e', b) = desugar_{expr}(\texttt{std.equals}(e, e'), b)
+            desugar_{expr}(e \mathop{==} e', b) = desugar_{expr}(\texttt{\$std.equals}(e, e'), b)
           \]
         </div>
 
         <div class="desugar-rule">
           \[
-            desugar_{expr}(e \mathop{\%} e', b) = desugar_{expr}(\texttt{std.mod}(e, e'), b)
+            desugar_{expr}(e \mathop{\%} e', b) = desugar_{expr}(\texttt{\$std.mod}(e, e'), b)
           \]
         </div>
 
         <div class="desugar-rule">
           \[
             desugar_{expr}(e \mathop{\texttt{in}} e', b) =
-                desugar_{expr}(\texttt{std.objectHasEx}(e', e, \texttt{true}), b)
+                desugar_{expr}(\texttt{\$std.objectHasEx}(e', e, \texttt{true}), b)
           \]
         </div>
 
         <div class="desugar-rule">
           \[
             desugar_{expr}(e \mathop{\texttt{in}} \texttt{super}, b) =
-                desugar_{expr}(\texttt{std.objectHasEx}(\texttt{super}, e, \texttt{true}), b)
+                desugar_{expr}(\texttt{\$std.objectHasEx}(\texttt{super}, e, \texttt{true}), b)
           \]
         </div>
       </div>
@@ -1484,8 +1484,8 @@ <h3 id="desugaring">Desugaring</h3>
             \hspace{10mm}\textrm{Let }arr, i\textrm{ fresh} \\
             \hspace{10mm}desugar_{expr}(
                 \local{arr = e'}{
-                    \texttt{std.join}(\\\hspace{20mm}[\ ], \texttt{std.makeArray}(
-                        \texttt{std.length}(arr),
+                    \texttt{\$std.join}(\\\hspace{20mm}[\ ], \texttt{\$std.makeArray}(
+                        \texttt{\$std.length}(arr),
                         \function{i}{\local{x = arr[i]}{desugar_{arrcomp}(e, compspec, b)}}
                     ))
                 },
@@ -1499,8 +1499,8 @@ <h3 id="desugaring">Desugaring</h3>
             \hspace{10mm}\textrm{Let }arr, i\textrm{ fresh} \\
             \hspace{10mm}desugar_{expr}(
                 \local{arr = e'}{
-                    \texttt{std.join}(\\\hspace{20mm}[\ ], \texttt{std.makeArray}(
-                        \texttt{std.length}(arr),
+                    \texttt{\$std.join}(\\\hspace{20mm}[\ ], \texttt{\$std.makeArray}(
+                        \texttt{\$std.length}(arr),
                         \function{i}{\local{x = arr[i]}{[e]}}
                     ))
                 },