[SR-6920] Unicode combining scalars interact wrongly with the start of a string literal. #49469
Comments
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The Swift parser doesn't currently take combining characters into account. |
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Disclaimer: We already have https://github.com/apple/swift/blob/master/include/swift/Basic/Unicode.h #include "swift/Basic/Unicode.h"
using swift::unicode;
/// Returns true if a quote followed by 'scalarAfterQuote' can be used as a quote.
bool isValidQuote(uint32_t scalarAfterQuote) {
if (scalarAfterQuote < 0x80)
return true;
auto GCBForQuoteMark = getGraphemeClusterBreakProperty('"');
auto GCBForFirstScalar = getGraphemeClusterBreakProperty(scalarAfterQuote);
// If 'scalarAfterQuote' is a EGC boundary, it's a valid quote.
return isExtendedGraphemeClusterBoundary(GCBForQuoteMark, GCBForFirstScalar);
}
// Check isValidQuote() for each quotes in string literal (and start quote)If we implement this, the following code should be valid. |
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Additional Detail from JIRA
md5: 493f3295b28807d82094414006ece57b
Issue Description:
This code should not compile, because these string literals should not have beginning quote characters:
```swift
let quote = "̠"
```
`{LATIN SMALL LETTER L}{LATIN SMALL LETTER E}{LATIN SMALL LETTER T}{SPACE}{LATIN SMALL LETTER Q}{LATIN SMALL LETTER U}{LATIN SMALL LETTER O}{LATIN SMALL LETTER T}{LATIN SMALL LETTER E}{SPACE}{EQUALS SIGN}{SPACE}{QUOTATION MARK}{COMBINING MINUS SIGN BELOW}{QUOTATION MARK}
`
To verify this, let us ask what swift strings think:
```swift
let quoteCount = """
```
The above returns that there is 1 quote, meaning it cannot be a valid string literal, yet it is.
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