Consider the case where we strip types from var x: number = 1 in preserve format mode. Whenever we print a node, the generator automatically keeps the original source position up to date with the original node position.

This means that we would print the Identifier("x"), and then set the original source position to the space after number (because : number is part of the identifier node). Then, when printing =, we'd first print the necessary spaces to catch up with the correct location ( ). Before doing that, .append() would insert a mapping, thus mapping the space right after x in the generated code to the one right after number in the original code.

This PR changes two things:

• when adding spaces for catching up, they do not cause a mapping to be injected
• after adding spaces, we update the sourcePosition to actually point to where we catched up to thanks to the spaces

This change helps shaving multiple KBs off from the preserveFormat test cases in #18006, but it's also a correctness fix on its own.