Support casting coalesce funcs (sqlc-dev#62)

Author: kyleconroy

internal/dinosql/parser.go

@@ -445,6 +445,9 @@ func outputColumns(c core.Catalog, node nodes.Node) ([]core.Column, error) {
 			if ref, ok := n.Arg.(nodes.ColumnRef); ok {
 				name = join(ref.Fields, "_")
 			}
+			if res.Name != nil {
+				name = *res.Name
+			}
 			// TODO Validate column names
 			col := catalog.ToColumn(n.TypeName)
 			col.Name = name

internal/dinosql/query_test.go

@@ -518,6 +518,20 @@ func TestQueries(t *testing.T) {
 				},
 			},
 		},
+		{
+			"cast coalesce",
+			`
+			CREATE TABLE foo (bar text);
+
+			SELECT coalesce(bar, '')::text as login
+			FROM foo;
+			`,
+			Query{
+				Columns: []core.Column{
+					{Name: "login", DataType: "text", NotNull: true},
+				},
+			},
+		},
 	} {
 		test := tc
 		t.Run(test.name, func(t *testing.T) {