ReSharper provides over 2500 code inspections in all supported languages. These inspections are used to detect and highlight code issues in design time in all opened files, and/or to find all code issues in specific scope, which can be as large as the entire solution.
To find out what kind of code inspections ReSharper provides, check out the full list of ReSharper code inspections in different languages.
Code inspections can be divided into the following groups:
ReSharper's own code inspections that include:
Inspections with the fixed severity level 'Error'. These inspections detect compiler errors and there is no way to disable or configure them.
Inspections with configurable severity levels, which detect the rest of code issues (for example, compiler warnings, runtime and logical errors, code smells, redundancies, improvement suggestions, and so on.). You can find these configurable inspections on the page of ReSharper options (Alt+R,,O). These inspections can be configured in several ways — you can suppress the detected issues with comments and attributes, disable them or change their severity level in settings or .editorconfig files.
Severity levels of code inspections
Each ReSharper code inspection as well as structural search and replace pattern has one of the following severity levels:
Code inspections that have the 'Error' severity level by default are aimed at code issues that either prevent your code from compiling or result in runtime errors. Most of these inspections are not configurable, that is you cannot disable them or change their severity level.
In design-time inspection, ReSharper displays unresolved symbols in red: and highlights erroneous statements or part of them with a red curly underline: If there is at least one error in the current file, the status indicator displays the Error icon, and red markers are shown for each error on the marker bar.
This severity level corresponds to compiler warnings and to other issues that do not prevent your code from compiling but may nevertheless represent serious coding inefficiencies. For example, ReSharper informs you about redundant type casts or namespace import directives, incorrect format strings, declared but never used local variables or private fields, unused private methods, and so on.
In design-time inspection, ReSharper displays redundant symbols with greyed text: and highlights statements or part of them with a blue curly underline: If there is at least one warning in the current file, the status indicator displays the Warning icon, and yellow markers are shown for each warning on the marker bar.
Code issues with this severity level provide insights into code structure, drawing your attention to things that aren't necessarily bad or wrong, but probably useful to know.
For instance, you might be interested to know that 'parameter can be declared with base type', meaning that your method only uses members of the parameter's base type. This can be an indication of a different error, such as failure to take into account the specifics of the actual parameter type. Based on this knowledge, you may want to change the parameter's type - or not, if that is by design.
In design-time inspection, ReSharper highlights suggestions with a green curly underline: and adds green markers for each warning on the marker bar.
This is the lowest severity level. Code issues with this severity bring your attention to a particular code detail and/or recommends a way of improvement.
In design-time inspection, ReSharper highlights hints by adding a dashed green underline to the initial two letters of the corresponding symbol: Unlike errors, warnings and suggestions, hints are not taken into account when you navigate between code issues in the editor, and not shown in the marker bar.
Note that when you set the caret over a highlighted hint, no popup is shown, the corresponding message only appears in the status bar.
Severity levels of most code inspections (except those detecting compiler errors) can be changed, that is you can define severity levels for each code inspection according to your needs.
Categories of code inspections
ReSharper groups configurable code inspections by several categories. These categories roughly define purposes of inspections and kinds of code issues that they detect. The categories are used to group code inspections on the page of ReSharper options (Alt+R,,O), and to group code issues found in specific scope and displayed in the Inspection Results window.
Potential Code Quality Issues
This category includes inspections that detect critical issues (code smells), mostly with Error or Warning level. This category also includes inspections that ensure localization assistance.
Redundancies in Code
Code inspections in this category look for redundancies and dead code, which affect code readability and style, and could be safely removed. Some code redundancies cannot be fixed automatically, and quick-fixes for them are performed in the interactive mode, requiring the user input. But the majority of the redundancies can be fixed without user interaction, using either fix in scope or code cleanup.
Language Usage Opportunities
This category includes code inspections, mostly with the suggestion severity level, which notify you when more advanced language constructs can be used. These inspections detect syntax of outdated language versions and suggest using features from more modern language versions. For most of the supported languages, language version can be detected automatically or set manually.
Inspections in this category detect violations of code syntax styles. In contrast to most of other code inspections, these inspections can either detect the same code construct as a code issue or not depending on the corresponding code style rule configured on the page of ReSharper options (Alt+R,,O). You can also fix issues that these inspection detect, using code cleanup.
This category includes code inspections, mostly with the warning severity level, which detect violations related to symbol attributes, including ReSharper's code annotations, and other similar issues.
Inspections in this category correspond to Clang compiler warnings integrated with ReSharper C++.
Clang Static Analyzer Checks
Inspections in this category are diagnostics from Clang Static Analyzer integrated with ReSharper C++.
All static analyzer checks are disabled by default, since enabling them significantly slows down Clang-Tidy.
Inspections in this category are specific to C++ code of Unreal Engine projects.
Identifiers of configurable code inspections
Each configurable code inspection has two unique identifiers that you can use to configure it. Let's take the Possible 'System.NullReferenceException' inspection as an example:
Inspection ID is used to suppress the inspection with a comment —// ReSharper disable once PossibleNullReferenceExceptionfor a single issue or// ReSharper disable PossibleNullReferenceExceptiontill the end of the file,
or with an attribute —[SuppressMessage("ReSharper", "PossibleNullReferenceException")].
Inspection EditorConfig property can be used to configure the inspection from .editorconfig files. For example, you can change the inspection's severity level to Error with the following line:resharper_possible_null_reference_exception_highlighting=error
You can find identifiers for each configurable inspection in the Code Inspection Index — just choose a language page and then use the browser search to find the details of the desired inspection.
List of configurable code inspections