fix expr parsing in brackets

Author: pfitzseb

src/components/operators.jl

@@ -243,7 +243,7 @@ function parse_unary_colon(ps::ParseState, op::EXPR)
         ret = op
     else
         prev_errored = ps.errored
-        arg = @precedence ps 20 parse_expression(ps)
+        arg = @precedence ps 20 @nocloser ps :inref parse_expression(ps)
         if isbracketed(arg) && headof(arg.args[1]) === :errortoken && errorof(arg.args[1]) === UnexpectedAssignmentOp
             ps.errored = prev_errored
             arg.args[1] = arg.args[1].args[1]

test/parser.jl

@@ -1270,4 +1270,23 @@ end
             @test test_expr("0x111111111111111111111111111111111")
         end
     end
+
+    @testset "#302" begin
+        str = """
+        const _examples = PlotExample[
+        PlotExample( # 1
+            "Lines",
+            "A simple line plot of the columns.",
+            [:(
+                begin
+                    plot(Plots.fakedata(50, 5), w = 3)
+                end
+            )],
+        ),
+        ]
+        """
+        @test test_expr(str)
+        x, ps = CSTParser.parse(CSTParser.ParseState(str), true)
+        @test ps.errored == false
+    end
 end