Read an F# triple-quoted literal that carries no layout - #771
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TryScanMultiLine rejected any multi-line literal whose content did not strip back to the layout convention. For C# that is right: a raw string not in that shape does not compile, so the content is something this never wrote. F# is the other case. Its triple-quoted literal is plain verbatim text and the layout is only an agreement between the code that renders a snapshot and the code that reads one back, so a hand-written literal with its content starting on the opening line - the idiomatic shape - is perfectly valid and its value is simply what it says. Rejecting those made them impossible to patch, and did so in the worst way: the two halves of the agreement disagreed. TryParse returned "not a string literal" while StripLayout, which is what a test library runs the value through, returned the same text unchanged, so the OriginalValue an F# producer sends as its anchor (FS0202 - no CallerArgumentExpression) could never match what the parser read. The snapshot reported "The expected argument of the call near line N is not a string literal" and stayed that way for the life of the file. Give TryScanMultiLine a layoutRequired flag: C# passes true, F# false and falls back to the verbatim newline-normalised content, which is the answer StripLayout already gives for the same text. ParseRejectsMalformedIndent pinned the old behaviour and becomes ParseKeepsContentWithNoLayoutToStrip, which also asserts the two readers agree.
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TryScanMultiLine rejected any multi-line literal whose content did not strip back to the layout convention. For C# that is right: a raw string not in that shape does not compile, so the content is something this never wrote.
F# is the other case. Its triple-quoted literal is plain verbatim text and the layout is only an agreement between the code that renders a snapshot and the code that reads one back, so a hand-written literal with its content starting on the opening line - the idiomatic shape - is perfectly valid and its value is simply what it says.
Rejecting those made them impossible to patch, and did so in the worst way: the two halves of the agreement disagreed. TryParse returned "not a string literal" while StripLayout, which is what a test library runs the value through, returned the same text unchanged, so the OriginalValue an F# producer sends as its anchor (FS0202 - no CallerArgumentExpression) could never match what the parser read. The snapshot reported "The expected argument of the call near line N is not a string literal" and stayed that way for the life of the file.
Give TryScanMultiLine a layoutRequired flag: C# passes true, F# false and falls back to the verbatim newline-normalised content, which is the answer StripLayout already gives for the same text. ParseRejectsMalformedIndent pinned the old behaviour and becomes ParseKeepsContentWithNoLayoutToStrip, which also asserts the two readers agree.