parse and compile argumentless lambdas

eval/compile.go

@@ -600,10 +600,15 @@ func (cp *compiler) popScope() {
 
 func (cp *compiler) lambda(n *parse.Primary) valuesOp {
 	// Collect argument names
-	argNames := make([]string, len(n.List.Compounds))
-	for i, arg := range n.List.Compounds {
-		name := mustString(cp, arg, "expect string")
-		argNames[i] = name
+	var argNames []string
+	if n.List != nil {
+		argNames = make([]string, len(n.List.Compounds))
+		for i, arg := range n.List.Compounds {
+			name := mustString(cp, arg, "expect string")
+			argNames[i] = name
+		}
+	} else {
+		argNames = []string{}
 	}
 
 	// XXX The fiddlings with cp.capture is likely wrong.

parse/parse.go

@@ -475,21 +475,12 @@ func (pn *Primary) lbracket(ps *parser) {
 			ps.error = shouldBeRBracket
 			return
 		}
-		if !parseSep(pn, ps, '{') {
-			// List
+		if parseSep(pn, ps, '{') {
+			pn.lambda(ps)
+		} else {
 			pn.Type = List
-			return
-		}
-		pn.Type = Lambda
-		if !startsChunk(ps.peek(), nil) && ps.peek() != '}' {
-			ps.error = shouldBeChunk
-			return
-		}
-		pn.setChunk(parseChunk(ps, nil))
-		if !parseSep(pn, ps, '}') {
-			ps.error = shouldBeRBrace
-			return
 		}
+
 	case r == '&':
 		pn.Type = Map
 		// parseSep(pn, ps, '&')
@@ -527,9 +518,16 @@ var (
 
 // Braced = '{' Compound { (','|'-') Compounds } '}'
 // Comma = { Space } [ ',' ] { Space }
-func (pn *Primary) braced(ps *parser) {
-	pn.Type = Braced
+func (pn *Primary) lbrace(ps *parser) {
 	parseSep(pn, ps, '{')
+
+	if r := ps.peek(); r == ';' || r == '\n' || isSpace(r) {
+		pn.lambda(ps)
+		return
+	}
+
+	pn.Type = Braced
+
 	// XXX: we don't actually know what happens with an empty Compound.
 	pn.addToBraced(parseCompound(ps, isBracedSep))
 	for isBracedSep(ps.peek()) {
@@ -550,6 +548,19 @@ func (pn *Primary) braced(ps *parser) {
 	}
 }
 
+// lambda parses a lambda expression. The opening brace has been seen.
+func (pn *Primary) lambda(ps *parser) {
+	pn.Type = Lambda
+	if !startsChunk(ps.peek(), nil) && ps.peek() != '}' {
+		ps.error = shouldBeChunk
+		return
+	}
+	pn.setChunk(parseChunk(ps, nil))
+	if !parseSep(pn, ps, '}') {
+		ps.error = shouldBeRBrace
+	}
+}
+
 func startsPrimary(r rune, cut runePred) bool {
 	if cut.matches(r) {
 		return false
@@ -584,7 +595,7 @@ func (pn *Primary) parse(ps *parser, cut runePred) {
 	case '[':
 		pn.lbracket(ps)
 	case '{':
-		pn.braced(ps)
+		pn.lbrace(ps)
 	default:
 		pn.bareword(ps, cut)
 	}

parse/parse_test.go

@@ -126,7 +126,7 @@ var goodCases = []struct {
 		ast{"Compound/Indexing/Primary", fs{"Type": Map, "text": "[ & ]"}},
 	)},
 	// Lambda
-	{"a []{} [ ]{ } []{ echo 233 } [ $x $y ]{puts $x $y}", a(
+	{"a []{} [ ]{ } []{ echo 233 } [ $x $y ]{puts $x $y} { put $1}", a(
 		ast{"Compound/Indexing/Primary", fs{
 			"Type": Lambda,
 		}},
@@ -142,6 +142,10 @@ var goodCases = []struct {
 			"List":  "$x $y ",
 			"Chunk": "puts $x $y",
 		}},
+		ast{"Compound/Indexing/Primary", fs{
+			"Type":  Lambda,
+			"Chunk": " put $1",
+		}},
 	)},
 	// Output capture
 	{"a () (b;c)", a(