Code inspection: Expression is always 'true' or always 'false'

This inspection is fairly obvious: ReSharper analyzes values and nullability, integer arithmetics, and so on, and suggests eliminating expressions that are always true or always false based on its analysis results.

The only problem with this inspection is that sometimes it's not obvious how ReSharper has come to this conclusion. Because of this, you may be unwilling to accept suggestions to replace expressions with explicit true or false, or to remove redundant checks in if statements. Below are some StackOverflow questions that illustrate this problem:

• Why does ReSharper tell me this expression is always true?

• How Does ReSharper Know “Expression is always true”?

• ReSharper bug? Incorrect “expression is always true”

• ReSharper claims that my expression is always true? Is it correct or is it a bug?

• ReSharper says this expression is always true. Why?

• Trying to understand why resharper told me expression is always false

• Why I getting an “Expression always true” warning?