Declaring FullPath instead of string

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These rules find the declarations that use string for a value that is always a FullPath. Declaring them as FullPath keeps the guarantee of the type, and lets the other rules find the string operations to replace. They are Info rules without a code fix: changing a declaration can affect its callers, so you make the change yourself.

The rules recognize a FullPath in all its string forms: fullPath, (string)fullPath, fullPath.Value, fullPath.RawValue and fullPath.ToString().

MFFP0011: Return FullPath instead of string

The rule reports a method or a local function that returns string when every value it returns is a FullPath, as in string GetOutputPath() => root / "output";. The return statements of the lambdas and local functions it contains are not taken into account.

It does not report a method that is override, virtual or abstract, or that implements an interface: its return type is not yours to change.

MFFP0012: Declare the property as FullPath instead of string

The rule reports a string property whose getter only returns FullPath values, such as public string Path => _path; where _path is a FullPath.

It does not report:

a property that has a setter, because changing its type also changes what callers can assign;
an indexer;
a property that is override, virtual or abstract, or that implements an interface.

MFFP0013: Declare the variable as FullPath instead of string

The rule reports a local variable declared as string whose initializer and assignments are all FullPath values, such as string path = fullPath;.

It does not report:

a variable declared with var: it already has the type of its initializer;
a variable passed by ref, out or in, or aliased by a ref local;
a variable used with a compound assignment, such as path += ".bak" or path ??= other;
a variable assigned by a deconstruction.

MFFP0014: Declare the parameter as FullPath instead of string

The rule reports a string parameter when every call of the method, in the project, passes a FullPath.

It only analyzes the methods whose callers are all in the project: it does not report a method visible outside the assembly, such as a public or protected method of a public type. It also does not report:

a method that is never called, or that is used as a delegate;
a string? parameter, because a FullPath cannot be null;
an optional, params, ref, out or in parameter;
a method that is override, virtual or abstract, or that implements an interface;
a constructor or an operator.

The rule looks at all the calls of the project, so it is reported when the whole project has been analyzed. Depending on the settings of your IDE, it may only appear in the build output.