[project @ 1998-06-08 11:45:09 by simonpj]

[ghc-hetmet.git] / ghc / compiler / parser / syntax.c

diff --git a/ghc/compiler/parser/syntax.c b/ghc/compiler/parser/syntax.c
index a48b119..4f8d661 100644 (file)
--- a/ghc/compiler/parser/syntax.c
+++ b/ghc/compiler/parser/syntax.c
@@ -127,6 +127,7 @@ expORpat(int wanted, tree e)
 
          case clitlit:
            error_if_patt_wanted(wanted, "``literal-literal'' in pattern");
+           break;
 
          default: /* the others only occur in pragmas */
            hsperror("not a valid literal pattern or expression");
@@ -317,6 +318,7 @@ lhs_is_patt(tree e)
       case llist:
       case tuple:
       case negate:
+      case record:
        expORpat(LEGIT_PATT, e);
        return TRUE;
 
@@ -326,13 +328,17 @@ lhs_is_patt(tree e)
       case ap:
        {
          tree f = function(e);
-         tree a = garg(e);       /* do not "unparen", otherwise the error
-                                      fromInteger ((x,y) {-no comma-} z)
-                                    will be missed.
-                                 */
 
-         /* definitions must have pattern arguments */
+/*  These lines appear to duplicate what's in function(e).
+    Nuked SLPJ May 97
+       
+         tree a = garg(e);       -- do not "unparen", otherwise the error
+                                 --     fromInteger ((x,y) {-no comma-} z)
+                                 --   will be missed.
+
+         -- definitions must have pattern arguments
          expORpat(LEGIT_PATT, a);
+*/
 
          if(ttree(f) == ident)
            return(isconstr(qid_to_string(gident(f))));
@@ -341,7 +347,7 @@ lhs_is_patt(tree e)
            return(lhs_is_patt(f));
 
          else
-           hsperror("Not a legal pattern binding in LHS");
+           hsperror("Syntax error: not a legal pattern binding in LHS");
        }
 
       case infixap:
@@ -362,7 +368,7 @@ lhs_is_patt(tree e)
 
       /* Anything else must be an illegal LHS */
       default:
-       hsperror("Not a valid LHS");
+       hsperror("Syntax error: not a valid LHS");
       }
 
   abort(); /* should never get here */
@@ -371,7 +377,8 @@ lhs_is_patt(tree e)
 
 
 /*
-  Return the function at the root of a series of applications.
+  Return the function at the root of a series of applications,
+  checking on the way that the arguments are patterns.
 */
 
 tree
@@ -533,9 +540,50 @@ checknobangs(app)
        hsperror("syntax error: unexpected ! in type");
 
       checknobangs(gtapp((struct Stapp *)app));
-    }    
+    }
+}
+
+
+/* Check that a type is of the form
+       C a1 a2 .. an
+   where n>=1, and the ai are all type variables
+   This is used to check that a class decl is well formed.
+*/
+void
+check_class_decl_head_help( app, n )
+  ttype app;
+  int n;       /* Number of args so far */
+{
+  switch (tttype(app)) {
+    case tapp:
+       /* Check the arg is a type variable */
+       switch (tttype (gtarg((struct Stapp *) app))) {
+               case namedtvar: break;
+               default: hsperror("Class declaration head must use only type variables");
+       }
+
+       /* Check the fun part */
+       check_class_decl_head_help( gtapp((struct Stapp *) app), n+1 );
+       break;
+
+    case tname:
+       /* Class name; check there is at least one argument */
+      if (n==0) {
+           hsperror("Class must have at least one argument");
+      }
+      break;
+
+    default:
+       hsperror("Illegal syntax in class declaration head");
+  }
 }
 
+void
+check_class_decl_head( app )
+  ttype app;
+{ check_class_decl_head_help( app, 0 ); }
+
+       
 
 /*
   Splits a tycon application into its constructor and a list of types.