/****************************************************************************
**
** Copyright (C) 2019 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Creator documentation.
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
**
****************************************************************************/

/*!
    \previouspage creator-highlighting.html
    \page creator-checking-code-syntax.html
    \nextpage creator-completing-code.html

    \title Checking Code Syntax

    As you write code, \QC checks code syntax. When \QC spots a syntax error in
    your code it underlines it and shows error details when you move the mouse
    pointer over the error. Similarly, when you are working on an instance of a
    JavaScript object notation (JSON) entity, \QC underlines errors in JSON data
    structure.

    \if defined(qtcreator)
    In the following screenshot, \QC points out an error, because a semicolon is
    missing at the end of the line:

    \image qtcreator-syntaxerror.png

    In the following screenshot, \QC issues a warning, because the variable is
    not used:

    \image qtcreator-semanticerror.png

    To modify the colors used for underlining errors and warnings, select
    \uicontrol Tools > \uicontrol Options > \uicontrol {Text Editor} >
    \uicontrol {Font & Colors} > \uicontrol Copy, and select new colors for
    \uicontrol Error and \uicontrol Warning.

    \section1 Viewing Annotations

    When using the Clang code model, errors and warnings are additionally marked
    with icons and annotated. If a \l{http://clang.llvm.org/diagnostics.html}
    {Clang fix-it} is available, you can execute it by clicking the
    \inlineimage refactormarker.png
    icon and pressing \key Enter.

    In the following screenshot, a Qt class name contains a typo:

    \image qtcreator-typo-clang.png

    You can use the icons in the tooltip popup to copy the error or
    warning message to the clipboard or to ignore and hide it. Select
    the \uicontrol {Annotation Settings} link to specify the position
    of the line annotations.

    In the following screenshot, a semicolon is missing at the end of the
    line.

    \image qtcreator-syntaxerror-clang.png

    In the following screenshot, the variable is not used.

    \image qtcreator-semanticerror-clang.png

    \else
    In addition to underlining, errors and warnings are marked with icons and
    annotated.
    \endif
    When writing QML or JavaScript code, the annotations may contain error codes
    listed in \l{JavaScript and QML Error Codes}.

    \image qml-syntax-check.png

    \section2 Specifying Line Annotation Positions

    To specify the position where the annotations are displayed, select
    \uicontrol Tools > \uicontrol Options > \uicontrol {Text Editor} >
    \uicontrol Display > \uicontrol {Line annotations}, and then select
    whether to display the annotations directly next to the code, aligned
    to the right of the code, or in the right margin. Showing annotations
    between lines can be useful if there is usually not enough space to
    display annotations next to the text.

    If you hide the annotations by deselecting the check box, you can move the
    mouse pointer over an icon to view them.

    \section1 JavaScript and QML Error Codes

    You can run static checks on the QML and JavaScript code in your project to
    find common problems. To run the checks, select \uicontrol Tools >
    \uicontrol {QML/JS} > \uicontrol {Run Checks} or press \key {Ctrl+Shift+C}.
    The results are shown in the \uicontrol QML and \uicontrol {QML Analysis}
    filters of the \uicontrol Issues output pane.

    Many of the error messages are similar to the ones in Douglas Crockford's
    \l{http://www.jslint.com}{JSLint} tool. For more information about JSLint
    errors, see \l{http://linterrors.com/js}{JSLint Error Explanations}.

    \table
    \header
        \li Id
        \li Severity
        \li Message
        \li Description

    \row
        \li M1
        \li Error
        \li Invalid value for enum
        \li

    \row
        \li M2
        \li Error
        \li Enum value must be a string or a number
        \li

    \row
        \li M3
        \li Error
        \li Number value expected
        \li

    \row
        \li M4
        \li Error
        \li Boolean value expected
        \li

    \row
        \li M5
        \li Error
        \li String value expected
        \li

    \row
        \li M6
        \li Error
        \li Invalid URL
        \li

    \row
        \li M7
        \li Warning
        \li File or directory does not exist
        \li

    \row
        \li M8
        \li Error
        \li Invalid color
        \li

    \row
        \li M9
        \li Error
        \li Anchor line expected
        \li

    \row
        \li M10
        \li Error
        \li Duplicate property binding
        \li See also: \l{http://linterrors.com/js/duplicate-key-a}
            {Duplicate key '{a}'}.

    \row
        \li M11
        \li Error
        \li Id expected
        \li See also:
            \l{http://linterrors.com/js/expected-an-identifier-and-instead-saw-a-a-reserved-word}
            {Expected an identifier and instead saw '{a}' (a reserved word)}.

    \row
        \li M14
        \li Error
        \li Invalid id
        \li See also:
            \l{http://linterrors.com/js/expected-an-identifier-and-instead-saw-a-a-reserved-word}
            {Expected an identifier and instead saw '{a}' (a reserved word)}.


    \row
        \li M15
        \li Error
        \li Duplicate id
        \li Ids in a file must be unique.
            See also: \l{http://linterrors.com/js/duplicate-key-a}
            {Duplicate key '{a}'}.

    \row
        \li M16
        \li Error
        \li Invalid property name \c name
        \li

    \row
        \li M17
        \li Error
        \li \c Name does not have members
        \li

    \row
        \li M18
        \li Error
        \li \c Field is not a member of \c object
        \li

    \row
        \li M19
        \li Warning
        \li Assignment in condition
        \li It could be a typing error. If it is intentional, wrap the
            assignment in parentheses.

    \row
        \li M20
        \li Warning
        \li Unterminated non-empty case block
        \li Case blocks should either be empty or end in a flow control
            statement such as \c break, \c return or \c continue.
            Alternatively you can indicate intentional fall through by ending
            with a \c {// fall through} comment.

    \row
        \li M23
        \li Warning
        \li Do not use \c eval
        \li See also: \l{http://linterrors.com/js/eval-is-evil}{eval is evil}.

    \row
        \li M28
        \li Warning
        \li Unreachable
        \li Indicates that the underlined statement will never be executed.

    \row
        \li M29
        \li Warning
        \li Do not use \c with
        \li See also: \l{http://linterrors.com/js/unexpected-with}
            {Unexpected 'with'}.

    \row
        \li M30
        \li Warning
        \li Do not use comma expressions
        \li

    \row
        \li M31
        \li Warning
        \li Unnecessary message suppression
        \li

    \row
        \li M103
        \li Warning
        \li \c Name is already a formal parameter
        \li

    \row
        \li M104
        \li Warning
        \li \c Name is already a function
        \li

    \row
        \li M105
        \li Warning
        \li Var \c name is used before its declaration
        \li

    \row
        \li M106
        \li Warning
        \li \c Name is already a var
        \li

    \row
        \li M107
        \li Warning
        \li \c Name is declared more than once
        \li Variables declared in a function are always visible everywhere in
            the function, even when declared in nested blocks or \c for
            statement conditions. Redeclaring a variable has no effect.

    \row
        \li M108
        \li Warning
        \li Function \c name is used before its declaration
        \li See also: \l{http://linterrors.com/js/a-was-used-before-it-was-defined}
            {{a} was used before it was defined}.

    \row
        \li M109
        \li Warning
        \li Do not use \c Boolean as a constructor
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M110
        \li Warning
        \li Do not use \c String as a constructor
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M111
        \li Warning
        \li Do not use \c Object as a constructor
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M112
        \li Warning
        \li Do not use \c Array as a constructor
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M113
        \li Warning
        \li Do not use \c Function as a constructor
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M114
        \li Hint
        \li The \c function keyword and the opening parenthesis should be
            separated by a single space
        \li See also: \l{http://linterrors.com/js/expected-exactly-one-space-between-a-and-b}
            {Expected exactly one space between {a} and {b}}.

    \row
        \li M115
        \li Warning
        \li Do not use stand-alone blocks
        \li Blocks do not affect variable scoping. Thus blocks that are not
            associated to \c if, \c while, etc. have no effect and should be
            avoided.

    \row
        \li M116
        \li Warning
        \li Do not use void expressions
        \li

    \row
        \li M117
        \li Warning
        \li Confusing pluses
        \li See also: \l{http://linterrors.com/js/confusing-pluses}
            {Confusing pluses}.

    \row
        \li M119
        \li Warning
        \li Confusing minuses
        \li See also: \l{http://linterrors.com/js/confusing-minuses}
            {Confusing minuses}.

    \row
        \li M121
        \li Hint
        \li Declare all function vars on a single line
        \li

    \row
        \li M123
        \li Hint
        \li Unnecessary parentheses
        \li

    \target m126
    \row
        \li M126
        \li Warning
        \li \c == and \c != may perform type coercion, use \c === or \c !== to
            avoid it
        \li The non-strict equality comparison is allowed to convert its
            arguments to a common type. That can lead to unexpected results such
            as \c {' \t\r\n' == 0} being true. Use the strict equality operators
            \c === and \c !== and be explicit about conversions you require.

    \row
        \li M127
        \li Warning
        \li Expression statements should be assignments, calls or delete
            expressions only
        \li

    \row
        \li M128
        \li Error
        \li A state cannot have the specified child item
        \li

    \row
        \li M201
        \li Hint
        \li Place var declarations at the start of a function
        \li See also:
            \l{http://linterrors.com/js/move-var-declarations-to-the-top-of-the-function}
            {Move 'var' declarations to the top of the function}.

    \row
        \li M202
        \li Hint
        \li Use only one statement per line
        \li

    \row
        \li M203
        \li Warning
        \li Imperative code is not supported in \QDS
        \li

    \row
        \li M204
        \li Warning
        \li This QML type is not supported in \QDS
        \li
    \row
        \li M205
        \li Warning
        \li Reference to parent QML type cannot be resolved correctly by \QDS
        \li

    \row
        \li M206
        \li Warning
        \li This visual property binding cannot be evaluated in the local
            context and might not show up in \QDS as expected
        \li

    \row
        \li M207
        \li Warning
        \li \QDS only supports states in the root QML type
        \li

    \row
        \li M208
        \li Error
        \li This id might be ambiguous and is not supported in \QDS.
        \li

    \row
        \li M209
        \li Error
        \li This type (type name) is not supported as a root element in
            \QDS.
        \li

    \row
        \li M220
        \li Error
        \li This type (type name) is not supported as a root element of a
            UI file (.ui.qml).
        \li

    \row
        \li M221
        \li Error
        \li This type (type name) is not supported in a UI file (.ui.qml).
        \li

    \row
        \li M222
        \li Error
        \li Functions are not supported in a UI file (.ui.qml).
        \li For a list of supported JavaScript functions, see
            \l{Supported Methods}.

    \row
        \li M223
        \li Error
        \li Java Script blocks are not supported in a UI file (.ui.qml).
        \li

    \row
        \li M224
        \li Error
        \li Behavior type is not supported in a UI file (.ui.qml).
        \li

    \row
        \li M225
        \li Error
        \li States are only supported in the root item in a UI file (.ui.qml).
        \li

    \row
        \li M226
        \li Error
        \li Referencing the parent of the root item is not supported in a
            UI file (.ui.qml).
        \li

    \row
        \li M300
        \li Error
        \li Unknown component
        \li

    \row
        \li M301
        \li Error
        \li Could not resolve the prototype \c name of \c object
        \li

    \row
        \li M302
        \li Error
        \li Could not resolve the prototype \c name
        \li

    \row
        \li M303
        \li Error
        \li Prototype cycle, the last non-repeated component is \c name
        \li

    \row
        \li M304
        \li Error
        \li Invalid property type \c name
        \li
    \row
        \li M305
        \li Warning
        \li \c == and \c != perform type coercion, use \c === or \c !== to
            avoid it
        \li See \l{m126}{M126}.
    \row
        \li M306
        \li Warning
        \li Calls of functions that start with an uppercase letter should use
            \c new
        \li By convention, functions that start with an uppercase letter
            are constructor functions that should only be used with \c new.

    \row
        \li M307
        \li Warning
        \li Use \c new only with functions that start with an uppercase letter
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M308
        \li Warning
        \li Do not use \c Number as a constructor
        \li See also: \l{http://linterrors.com/js/do-not-use-a-as-a-constructor}
            {Do not use {a} as a constructor}.

    \row
        \li M309
        \li Hint
        \li Use spaces around binary operators
        \li

    \row
        \li M310
        \li Warning
        \li Unintentional empty block, use ({}) for empty object literal
        \li

    \row
        \li M311
        \li Hint
        \li Use \c type instead of \c var or \c variant to improve performance
        \li

    \row
        \li M312
        \li Error
        \li Missing property \c number
        \li

    \row
        \li M313
        \li Error
        \li Object value expected
        \li

    \row
        \li M314
        \li Error
        \li Array value expected
        \li

    \row
        \li M315
        \li Error
        \li \c Value value expected
        \li

    \row
        \li M316
        \li Error
        \li Maximum number value is \c number
        \li

    \row
        \li M317
        \li Error
        \li Minimum number value is \c number
        \li

    \row
        \li M318
        \li Error
        \li Maximum number value is exclusive
        \li

    \row
        \li M319
        \li Error
        \li Minimum number value is exclusive
        \li

    \row
        \li M320
        \li Error
        \li String value does not match required pattern
        \li

    \row
        \li M321
        \li Error
        \li Minimum string value length is \c number
        \li

    \row
        \li M322
        \li Error
        \li Maximum string value length is \c number
        \li

    \row
        \li M323
        \li Error
        \li \c Number elements expected in array value
        \li See also:
            \l{http://linterrors.com/js/the-array-literal-notation-is-preferrable}
            {The array literal notation [] is preferable}.

    \row
        \li M324
        \li Error
        \li Hit maximum recursion limit visiting AST, the code model will be unreliable
            and most likely invalid
        \li

    \row
        \li M400
        \li Warning
        \li Duplicate import
        \li

    \endtable

    \section1 Resetting the Code Model

    If you change the build and run kit when you have QML files open in the code
    editor, the code model might become corrupt. The following error message
    indicates that this might have happened: \e{Using Qt Quick 1 code model
    instead of Qt Quick 2}.

    You can see the error message when you move the mouse pointer over code that
    \QC underlines in the code editor or when you open a QML file in \QDS.

    To reset the code model, select \uicontrol Tools > \uicontrol {QML/JS} >
    \uicontrol {Reset Code Model}.

    \if defined(qtcreator)
    If this does not help, try changing the QML emulation layer to the one that
    was built with the same Qt version as the one selected in the build and run
    kit.
    \endif

    \section1 Inspecting QML and JavaScript

    To inspect QML and JavaScript properties, methods, and enums, move the
    cursor over them and select \uicontrol Tools > \uicontrol {QML/JS} >
    \uicontrol {Inspect API for Element Under Cursor}.

    \section1 Automatically Formatting QML/JS Files

    To automatically format QML/JS files upon saving, select \uicontrol Tools >
    \uicontrol Options > \uicontrol {Qt Quick} > \uicontrol {QML/JS Editing} >
    \uicontrol {Enable auto format on file save}.
*/
