Analyze match expression default cases

analyzer/control-flow_test.go

@@ -33,6 +33,16 @@ U: (| Int F64)
 `)
 }
 
+func TestMatchDefault (test *testing.T) {
+testString (test,
+`
+U: (| Int F64)
+[isInt u:U]:Bool = match u
+	| u:Int [return true]
+	* false
+`)
+}
+
 func TestMatchUnionUnderComplete (test *testing.T) {
 testString (test,
 `

analyzer/expression.go

@@ -759,7 +759,21 @@ func (this *Tree) analyzeMatch (
 		match.CaseMap[hash] = cas
 	}
 
-	if into != nil && len(match.Cases) < len(rawUnion.Allowed) {
+	if match.Default != nil {
+		this.pushScope(match.Default)
+		expression, err := this.analyzeExpression (
+			into, mode,
+			match.Default.Expression)
+		this.popScope()
+		
+		if err != nil { return nil, err }
+		match.Default.Expression = expression
+	}
+
+	allCasesCovered :=
+		len(match.Cases) == len(rawUnion.Allowed) ||
+		match.Default != nil
+	if into != nil && !allCasesCovered {
 		return nil, errors.Errorf (
 			match.Position(),
 			"match does not cover all types within %v",
@@ -772,7 +786,7 @@ func (this *Tree) analyzeMatch (
 }
 
 func (this *Tree) assembleMatchMap (match *entity.Match) (*entity.Match, error) {
-	match.CaseMap   = make(map[entity.Hash] *entity.Case)
+	match.CaseMap   = make(map[entity.Hash] *entity.MatchCase)
 	match.CaseOrder = make([]entity.Hash, len(match.Cases))
 	for index, cas := range match.Cases {
 		hash := cas.Declaration.Ty.Hash()