Error conditions for flexible doc strings
-----
<?php

<<<A
 @@{ "\t" }@@A;

<<<A
    FooBar
 @@{ "\t" }@@A;

echo <<<END
@@{ "\t" }@@   X
@@{ "\t\t" }@@END;

echo <<<END
      a
     b
    c
     END;

<<<END
\ta
@@{ "\t" }@@END;

<<<TEST
  Foo
$var
  TEST;

<<<TEST
$var
 TEST;

echo <<<END
 a
$a
 END;
-----
Invalid indentation - tabs and spaces cannot be mixed from 4:1 to 4:3
Invalid indentation - tabs and spaces cannot be mixed from 8:1 to 8:3
Invalid indentation - tabs and spaces cannot be mixed from 10:6 to 12:5
Invalid body indentation level (expecting an indentation level of at least 5) from 14:6 to 18:8
Invalid body indentation level (expecting an indentation level of at least 1) from 20:1 to 22:4
Invalid body indentation level (expecting an indentation level of at least 2) from 25:1 to 26:0
Invalid body indentation level (expecting an indentation level of at least 1) from 30:1 to 30:4
Invalid body indentation level (expecting an indentation level of at least 1) from 34:1 to 35:0
array(
    0: Stmt_Expression(
        expr: Scalar_String(
            value:
        )
    )
    1: Stmt_Expression(
        expr: Scalar_String(
            value:     FooBar
        )
    )
    2: Stmt_Echo(
        exprs: array(
            0: Scalar_String(
                value:   X
            )
        )
    )
    3: Stmt_Echo(
        exprs: array(
            0: Scalar_String(
                value:  a
                b
                c
            )
        )
    )
    4: Stmt_Expression(
        expr: Scalar_String(
            value: 	a
        )
    )
    5: Stmt_Expression(
        expr: Scalar_InterpolatedString(
            parts: array(
                0: InterpolatedStringPart(
                    value: Foo

                )
                1: Expr_Variable(
                    name: var
                )
            )
        )
    )
    6: Stmt_Expression(
        expr: Scalar_InterpolatedString(
            parts: array(
                0: Expr_Variable(
                    name: var
                )
            )
        )
    )
    7: Stmt_Echo(
        exprs: array(
            0: Scalar_InterpolatedString(
                parts: array(
                    0: InterpolatedStringPart(
                        value: a

                    )
                    1: Expr_Variable(
                        name: a
                    )
                )
            )
        )
    )
)