* Simplify @-patterns: only `{attrs}@name' or `name@{attrs}' are now

  allowed.  So `name1@name2', `{attrs1}@{attrs2}' and so on are now no
  longer legal.  This is no big loss because they were not useful
  anyway.

  This also changes the output of builtins.toXML for @-patterns
  slightly.

1 files changed, 38 insertions, 98 deletions

diff --git a/src/libexpr/eval-test.cc b/src/libexpr/eval-test.cc
index 27cf685f9de4..71b16384bec6 100644
--- a/src/libexpr/eval-test.cc
+++ b/src/libexpr/eval-test.cc
@@ -111,91 +111,6 @@ Env * allocEnv()
 }
 
 
-static bool patternIsStrict(Pattern pat)
-{
-    ATerm name, ellipsis, pat1, pat2;
-    ATermList formals;
-    if (matchVarPat(pat, name)) return false;
-    else if (matchAttrsPat(pat, formals, ellipsis)) return true;
-    else if (matchAtPat(pat, pat1, pat2))
-        return patternIsStrict(pat1) || patternIsStrict(pat2);
-    else abort();
-}
-
-
-static void bindVarPats(Pattern pat, Env & newEnv,
-    Env * argEnv, Expr argExpr, Value * & vArg)
-{
-    Pattern pat1, pat2;
-    if (matchAtPat(pat, pat1, pat2)) {
-        bindVarPats(pat1, newEnv, argEnv, argExpr, vArg);
-        bindVarPats(pat2, newEnv, argEnv, argExpr, vArg);
-        return;
-    }
-
-    ATerm name;
-    if (!matchVarPat(pat, name)) abort();
-
-    if (vArg) {
-        Value & v = newEnv.bindings[aterm2String(name)];
-        v.type = tCopy;
-        v.val = vArg;
-    } else {
-        vArg = &newEnv.bindings[aterm2String(name)];
-        vArg->type = tThunk;
-        vArg->thunk.env = argEnv;
-        vArg->thunk.expr = argExpr;
-    }
-}
-
-
-static void bindAttrPats(Pattern pat, Env & newEnv,
-    Value & vArg, Value * & vArgInEnv)
-{
-    Pattern pat1, pat2;
-    if (matchAtPat(pat, pat1, pat2)) {
-        bindAttrPats(pat1, newEnv, vArg, vArgInEnv);
-        bindAttrPats(pat2, newEnv, vArg, vArgInEnv);
-        return;
-    }
-    
-    ATerm name;
-    if (matchVarPat(pat, name)) {
-        if (vArgInEnv) {
-            Value & v = newEnv.bindings[aterm2String(name)];
-            v.type = tCopy;
-            v.val = vArgInEnv;
-        } else {
-            vArgInEnv = &newEnv.bindings[aterm2String(name)];
-            *vArgInEnv = vArg;
-        }
-        return;
-    }
-
-    ATerm ellipsis;
-    ATermList formals;
-    if (matchAttrsPat(pat, formals, ellipsis)) {
-        for (ATermIterator i(formals); i; ++i) {
-            Expr name, def;
-            DefaultValue def2;
-            if (!matchFormal(*i, name, def2)) abort(); /* can't happen */
-
-            Bindings::iterator j = vArg.attrs->find(aterm2String(name));
-            if (j == vArg.attrs->end())
-                throw TypeError(format("the argument named `%1%' required by the function is missing")
-                    % aterm2String(name));
-            
-            Value & v = newEnv.bindings[aterm2String(name)];
-            v.type = tCopy;
-            v.val = &j->second;
-        }
-        return;
-    }
-
-    abort();
-}
-
-
 static void eval(Env * env, Expr e, Value & v)
 {
     printMsg(lvlError, format("eval: %1%") % e);
@@ -279,16 +194,44 @@ static void eval(Env * env, Expr e, Value & v)
         Env * env2 = allocEnv();
         env2->up = env;
 
-        if (patternIsStrict(v.lambda.pat)) {
-            Value vArg;
-            eval(env, arg, vArg);
-            if (vArg.type != tAttrs) throw TypeError("expected attribute set");
-            Value * vArg2 = 0;
-            bindAttrPats(v.lambda.pat, *env2, vArg, vArg2);
-        } else {
-            Value * vArg = 0;
-            bindVarPats(v.lambda.pat, *env2, env, arg, vArg);
+        ATermList formals; ATerm ellipsis;
+
+        if (matchVarPat(v.lambda.pat, name)) {
+            Value & vArg = env2->bindings[aterm2String(name)];
+            vArg.type = tThunk;
+            vArg.thunk.env = env;
+            vArg.thunk.expr = arg;
+        }
+
+        else if (matchAttrsPat(v.lambda.pat, formals, ellipsis, name)) {
+            Value * vArg;
+            Value vArg_;
+
+            if (name == sNoAlias)
+                vArg = &vArg_;
+            else 
+                vArg = &env2->bindings[aterm2String(name)];
+
+            eval(env, arg, *vArg);
+            if (vArg->type != tAttrs) throw TypeError("expected attribute set");
+            
+            for (ATermIterator i(formals); i; ++i) {
+                Expr name, def;
+                DefaultValue def2;
+                if (!matchFormal(*i, name, def2)) abort(); /* can't happen */
+
+                Bindings::iterator j = vArg->attrs->find(aterm2String(name));
+                if (j == vArg->attrs->end())
+                    throw TypeError(format("the argument named `%1%' required by the function is missing")
+                    % aterm2String(name));
+            
+                Value & v = env2->bindings[aterm2String(name)];
+                v.type = tCopy;
+                v.val = &j->second;
+            }            
         }
+
+        else abort();
         
         eval(env2, v.lambda.body, v);
         return;
@@ -319,13 +262,10 @@ void run(Strings args)
     doTest("rec { x = 1; y = x; }.y");
     doTest("(x: x) 1");
     doTest("(x: y: y) 1 2");
-    doTest("(x@y: x) 1");
-    doTest("(x@y: y) 2");
-    doTest("(x@y@z: y) 3");
     doTest("x: x");
     doTest("({x, y}: x) { x = 1; y = 2; }");
     doTest("({x, y}@args: args.x) { x = 1; y = 2; }");
-    doTest("({x, y}@args@args2: args2.x) { x = 1; y = 2; }");
+    doTest("(args@{x, y}: args.x) { x = 1; y = 2; }");
     
     //Expr e = parseExprFromString(state, "let x = \"a\"; in x + \"b\"", "/");
     //Expr e = parseExprFromString(state, "(x: x + \"b\") \"a\"", "/");