[MOREL-36] In record pattern, make labels optional, and disallow "...…

…" anywhere but end

docs/reference.md

@@ -172,7 +172,7 @@ In Standard ML but not in Morel:
     | '<b>[</b>' <i>pat<sub>1</sub></i> <b>,</b> ... <b>,</b> <i>pat<sub>n</sub></i> '<b>]</b>' list (n &ge; 0)
 <i>patrow</i> &rarr; '<b>...</b>'                  wildcard
     | <i>lab</i> <b>=</b> <i>pat</i> [<b>,</b> <i>patrow</i>]      pattern
-    | <i>id</i> [<b>,</b> <i>patrow</i>]             variable
+    | <i>id</i> [<b>,</b> <i>patrow</i>]             label as variable
 </pre>
 
 ### Types

src/main/javacc/MorelParser.jj

@@ -1095,28 +1095,36 @@ Pat atomPat() :
   <LBRACE> {
     span = Span.of(getPos());
     final Map<String, Pat> map = new LinkedHashMap<>();
-    final boolean[] ellipsis = {false};
+    boolean ellipsis = false;
   }
-  recordPat(ellipsis, map)
-  (
-    <COMMA> recordPat(ellipsis, map)
-  )*
+  [
+    <ELLIPSIS> { ellipsis = true; }
+  |
+    recordPat(map)
+    (
+      LOOKAHEAD(2)
+      <COMMA> recordPat(map)
+    )*
+    [ <COMMA> <ELLIPSIS> { ellipsis = true; } ]
+  ]
   <RBRACE> {
-    return ast.recordPat(span.end(this), ellipsis[0], map);
+    return ast.recordPat(span.end(this), ellipsis, map);
   }
 }
 
 /** Parses a "label = pat" inside a record pattern. */
-void recordPat(boolean[] ellipsis, Map<String, Pat> map) :
+void recordPat(Map<String, Pat> map) :
 {
   final String id;
   final Ast.Pat pat;
 }
 {
-  <ELLIPSIS> { ellipsis[0] = true; }
-|
   ( <NON_NEGATIVE_INTEGER_LITERAL> | <IDENTIFIER> ) { id = token.image; }
-  <EQ> pat = pat() { map.put(id, pat); }
+  (
+    <EQ> pat = pat() { map.put(id, pat); }
+  |
+    { map.put(id, ast.idPat(getPos(), id)); }
+  )
 }
 
 /** Parses a type. */
@@ -1135,23 +1143,21 @@ Ast.Type atomicType() :
   <LPAREN> {
     span = Span.of(getPos());
   }
+  type = type()
   (
-    type = type()
+    <RPAREN> { return type; }
+  |
+    {
+      final List<Type> list = new ArrayList<>();
+      list.add(type);
+      Type type2;
+    }
     (
-      <RPAREN> { return type; }
-    |
-      {
-        final List<Type> list = new ArrayList<>();
-        list.add(type);
-        Type type2;
-      }
-      (
-        <COMMA> type2 = type() { list.add(type2); }
-      )+
-      <RPAREN> {
-        return ast.compositeType(span.end(this), list);
-      }
-    )
+      <COMMA> type2 = type() { list.add(type2); }
+    )+
+    <RPAREN> {
+      return ast.compositeType(span.end(this), list);
+    }
   )
 }
 

src/test/java/net/hydromatic/morel/MainTest.java

@@ -272,7 +272,7 @@ public void describeTo(Description description) {
     ml("case 1 of 0 => \"zero\" | _ => \"nonzero\"").assertParseSame();
     ml("case {a = 1, b = 2} of {a = 1, ...} => 1").assertParseSame();
     ml("case {a = 1, b = 2} of {...} => 1").assertParseSame();
-    ml("case {a = 1, b = 2} of {..., a = 3} => 1")
+    ml("case {a = 1, b = 2} of {a = 3, ...} => 1")
         .assertParse("case {a = 1, b = 2} of {a = 3, ...} => 1");
 
     // fn
@@ -346,6 +346,13 @@ public void describeTo(Description description) {
         .assertParseThrows(
             throwsA(IllegalArgumentException.class,
                 is("cannot derive label for expression b + c")));
+
+    ml("case x of {a = a, b} => a + b")
+        .assertParse("case x of {a = a, b = b} => a + b");
+    ml("case x of {a, b = 2, ...} => a + b")
+        .assertParse("case x of {a = a, b = 2, ...} => a + b");
+    ml("fn {a, b = 2, ...} => a + b")
+        .assertParse("fn {a = a, b = 2, ...} => a + b");
   }
 
   /** Tests the name of {@link TypeVar}. */
@@ -414,6 +421,8 @@ public void describeTo(Description description) {
         .assertType("int -> int * int -> int");
     ml("fn (x, y) => (x + 1, fn z => (x + z, y + z), y)")
         .assertType("int * int -> int * (int -> int * int) * int");
+    ml("fn {a = x, b = y, c} => x + y")
+        .assertType("{a:int, b:int, c:'a} -> int");
   }
 
   @Test public void testTypeLetRecFn() {
@@ -848,9 +857,19 @@ private <T extends Throwable> Matcher<Throwable> throwsA(Class<T> clazz,
   @Test public void testRecordMatch() {
     final String ml = "case {a=1, b=2, c=3}\n"
         + "  of {a=2, b=2, c=3} => 0\n"
-        + "   | {a=1, ..., c=x} => x\n"
+        + "   | {a=1, c=x, ...} => x\n"
         + "   | _ => ~1";
     ml(ml).assertEval(is(3));
+    ml("fn {} => 0").assertParseSame();
+    ml("fn {a=1, ..., c=2}")
+        .assertParseThrows(
+            throwsA(ParseException.class,
+                containsString("Encountered \" \",\" \", \"\" at line 1, "
+                    + "column 13.")));
+    ml("fn {...} => 0").assertParseSame();
+    ml("fn {a = a, ...} => 0").assertParseSame();
+    ml("fn {a, b = {c, d}, ...} => 0")
+        .assertParse("fn {a = a, b = {c = c, d = d}, ...} => 0");
   }
 
   @Test public void testRecordCase() {

src/test/resources/script/fixedPoint.sml

@@ -236,9 +236,9 @@ val edges =
 fun shortest_path edges =
   let
     val vertices =
-      from v in (from {source = s, target = _, weight = _} in edges yield s)
+      from v in (from {source, target, weight} in edges yield source)
           union
-          (from {source = _, target = t, weight = _} in edges yield t)
+          (from {source, target, weight} in edges yield target)
         group v
     val edges0 =
       from e in edges

src/test/resources/script/fixedPoint.sml.out

@@ -354,9 +354,9 @@ val edges =
 fun shortest_path edges =
   let
     val vertices =
-      from v in (from {source = s, target = _, weight = _} in edges yield s)
+      from v in (from {source, target, weight} in edges yield source)
           union
-          (from {source = _, target = t, weight = _} in edges yield t)
+          (from {source, target, weight} in edges yield target)
         group v
     val edges0 =
       from e in edges

src/test/resources/script/relational.sml

@@ -541,6 +541,7 @@ from (left, 2) in [(1, 2), (3, 4), (5, 2)]
 
 (*) Record pattern
 from {b = b, a = a} in [{a=1,b=2}];
+from {b, a} in [{a=1,b=2}];
 from {a = a, b = b} in [{a=1,b=2}];
 from {b = a, a = b} in [{a=1,b=2}];
 from {b = c, c = a, a = b} in [{a=1,b=2,c=3}];
@@ -555,8 +556,9 @@ from {a = c, b = true, c = a} in [{a=1,b=true,c=3}];
 from {a = c, b = true, c = a} in [{a=1,b=true,c=3},{a=1,b=true,c=4}] group c compute sum of a;
 from {a = a, b = b, c = _} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
 from {a = a, b = b, c = _} in [{a=1,b=true,c=3},{a=1,b=true,c=4}], d in ["a", "b"];
-from {a = a, ..., b = b} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
-from {a = a, ..., c = c} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
+from {a = a, b = b, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
+from {a = a, c = c, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
+from {a, c, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
 from {a = a, c = c, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
 from {b = y, ...} in [{a=1,b=2}];
 from {b = y, a = (p, q)} in [{a=(1,true),b=2}];
@@ -577,6 +579,13 @@ fun listFields lists =
 listFields [];
 listFields [{a = 1, b = 2}, {a = 3, b = 0}, {a = 4, b = 5}];
 
+(*) As above, using abbreviated record pattern
+fun listFields2 lists =
+  from {a, b} in lists
+  yield a + 1;
+listFields [];
+listFields [{a = 1, b = 2}, {a = 3, b = 0}, {a = 4, b = 5}];
+
 (*) Temporary functions
 let
   fun abbrev s =
@@ -638,7 +647,7 @@ from t in triples order t.foo 1; (* 1+2 < 2+6 = 3+5 *)
 from t in triples order t.foo 1, t.x; (* (1+2,1) < (2+6,2) < (3+5,3) *)
 from t in triples order t.foo 1, t.x desc; (* (1+2,~1) < (3+5,~3) < (2+6,~2) *)
 from t in triples order t.foo ~1, t.y; (* (~1+2,2) < (~3+5,5) < (~2+6,6) *)
-from {foo=foo,x=x,y=y} in triples
+from {foo,x,y} in triples
   order foo ~1, x; (* (~1+2,2) < (~3+5,5) < (~2+6,6) *)
 from t1 in triples, t2 in triples
   where t1.y = t2.y

src/test/resources/script/relational.sml.out

@@ -846,6 +846,9 @@ val it = [1,5] : int list
 from {b = b, a = a} in [{a=1,b=2}];
 val it = [{a=1,b=2}] : {a:int, b:int} list
 
+from {b, a} in [{a=1,b=2}];
+val it = [{a=1,b=2}] : {a:int, b:int} list
+
 from {a = a, b = b} in [{a=1,b=2}];
 val it = [{a=1,b=2}] : {a:int, b:int} list
 
@@ -886,10 +889,13 @@ val it =
   [{a=1,b=true,d="a"},{a=1,b=true,d="b"},{a=1,b=true,d="a"},{a=1,b=true,d="b"}]
   : {a:int, b:bool, d:string} list
 
-from {a = a, ..., b = b} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
+from {a = a, b = b, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
 val it = [{a=1,b=true},{a=1,b=true}] : {a:int, b:bool} list
 
-from {a = a, ..., c = c} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
+from {a = a, c = c, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
+val it = [{a=1,c=3},{a=1,c=4}] : {a:int, c:int} list
+
+from {a, c, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
 val it = [{a=1,c=3},{a=1,c=4}] : {a:int, c:int} list
 
 from {a = a, c = c, ...} in [{a=1,b=true,c=3},{a=1,b=true,c=4}];
@@ -938,6 +944,19 @@ listFields [{a = 1, b = 2}, {a = 3, b = 0}, {a = 4, b = 5}];
 val it = [2,4,5] : int list
 
 
+(*) As above, using abbreviated record pattern
+fun listFields2 lists =
+  from {a, b} in lists
+  yield a + 1;
+val listFields2 = fn : {a:int, b:'a} list -> int list
+
+listFields [];
+val it = [] : int list
+
+listFields [{a = 1, b = 2}, {a = 3, b = 0}, {a = 4, b = 5}];
+val it = [2,4,5] : int list
+
+
 (*) Temporary functions
 let
   fun abbrev s =
@@ -1057,7 +1076,7 @@ from t in triples order t.foo ~1, t.y;
 val it = [{foo=fn,x=1,y=2},{foo=fn,x=3,y=5},{foo=fn,x=2,y=6}]
   : {foo:int -> int, x:int, y:int} list
  (* (~1+2,2) < (~3+5,5) < (~2+6,6) *)
-from {foo=foo,x=x,y=y} in triples
+from {foo,x,y} in triples
   order foo ~1, x;
 val it = [{foo=fn,x=1,y=2},{foo=fn,x=3,y=5},{foo=fn,x=2,y=6}]
   : {foo:int -> int, x:int, y:int} list