Weird suggestions that aren't valid
I go into my project today to find my code replaced in several locations with things like the following:

From the colon on is what I did not write, the text in yellow.
When I click on it or hover over it it changes to this:

When I click on it I can't find a way to change it back to the suggestion.
When I change it to the suggestion, it turns out it's not valid:

What is happening?
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Hi, what you see is called Code Folding, and can be disabled via Settings/Preferences | Editor | CodeFolding | Go | One line returns/One line panics.
These are not suggestions on how to write the code, just ways for the IDE to represent how the code looks like.
When the IDE has a suggestion about the code, you'll find it using the Alt+Enter combination.