private ExpressionSyntax ParseInterpolatedStringToken()
{
// We don't want to make the scanner stateful (between tokens) if we can possibly avoid it.
// The approach implemented here is
//
// (1) Scan the whole interpolated string literal as a single token. Now the statefulness of
// the scanner (to match { }'s) is limited to its behavior while scanning a single token.
//
// (2) When the parser gets such a token, here, it spins up another scanner / parser on each of
// the holes and builds a tree for the whole thing (resulting in an InterpolatedStringExpressionSyntax).
//
// (3) The parser discards the original token and replaces it with this tree. (In other words,
// it replaces one token with a different set of tokens that have already been parsed)
//
// (4) On an incremental change, we widen the invalidated region to include any enclosing interpolated
// string nonterminal so that we never reuse tokens inside a changed interpolated string.
//
// This has the secondary advantage that it can reasonably be specified.
//
// The substitution will end up being invisible to external APIs and clients such as the IDE, as
// they have no way to ask for the stream of tokens before parsing.
//
var originalToken = this.EatToken();
var originalText = originalToken.ValueText; // this is actually the source text
Debug.Assert(originalText[0] == '$' || originalText[0] == '@');
var isAltInterpolatedVerbatim = originalText.Length > 2 && originalText[0] == '@'; // @$
var isVerbatim = isAltInterpolatedVerbatim || (originalText.Length > 2 && originalText[1] == '@');
Debug.Assert(originalToken.Kind == SyntaxKind.InterpolatedStringToken);
var interpolations = ArrayBuilder <Lexer.Interpolation> .GetInstance();
SyntaxDiagnosticInfo error = null;
bool closeQuoteMissing;
using (var tempLexer = new Lexer(Text.SourceText.From(originalText), this.Options, allowPreprocessorDirectives: false))
{
// compute the positions of the interpolations in the original string literal, and also compute/preserve
// lexical errors
var info = default(Lexer.TokenInfo);
tempLexer.ScanInterpolatedStringLiteralTop(interpolations, isVerbatim, ref info, ref error, out closeQuoteMissing);
}
// Make a token for the open quote $" or $@" or @$"
var openQuoteIndex = isVerbatim ? 2 : 1;
Debug.Assert(originalText[openQuoteIndex] == '"');
var openQuoteKind = isVerbatim
? SyntaxKind.InterpolatedVerbatimStringStartToken // $@ or @$
: SyntaxKind.InterpolatedStringStartToken; // $
var openQuoteText = isAltInterpolatedVerbatim
? "@$\""
: isVerbatim
? "$@\""
: "$\"";
var openQuote = SyntaxFactory.Token(originalToken.GetLeadingTrivia(), openQuoteKind, openQuoteText, openQuoteText, trailing: null);
if (isAltInterpolatedVerbatim)
{
openQuote = CheckFeatureAvailability(openQuote, MessageID.IDS_FeatureAltInterpolatedVerbatimStrings);
}
// Make a token for the close quote " (even if it was missing)
var closeQuoteIndex = closeQuoteMissing ? originalText.Length : originalText.Length - 1;
Debug.Assert(closeQuoteMissing || originalText[closeQuoteIndex] == '"');
var closeQuote = closeQuoteMissing
? SyntaxFactory.MissingToken(SyntaxKind.InterpolatedStringEndToken).TokenWithTrailingTrivia(originalToken.GetTrailingTrivia())
: SyntaxFactory.Token(null, SyntaxKind.InterpolatedStringEndToken, originalToken.GetTrailingTrivia());
var builder = _pool.Allocate <InterpolatedStringContentSyntax>();
if (interpolations.Count == 0)
{
// In the special case when there are no interpolations, we just construct a format string
// with no inserts. We must still use String.Format to get its handling of escapes such as {{,
// so we still treat it as a composite format string.
var text = Substring(originalText, openQuoteIndex + 1, closeQuoteIndex - 1);
if (text.Length > 0)
{
var token = MakeStringToken(text, text, isVerbatim, SyntaxKind.InterpolatedStringTextToken);
builder.Add(SyntaxFactory.InterpolatedStringText(token));
}
}
else
{
for (int i = 0; i < interpolations.Count; i++)
{
var interpolation = interpolations[i];
// Add a token for text preceding the interpolation
var text = Substring(originalText, (i == 0) ? (openQuoteIndex + 1) : (interpolations[i - 1].CloseBracePosition + 1), interpolation.OpenBracePosition - 1);
if (text.Length > 0)
{
var token = MakeStringToken(text, text, isVerbatim, SyntaxKind.InterpolatedStringTextToken);
builder.Add(SyntaxFactory.InterpolatedStringText(token));
}
// Add an interpolation
var interp = ParseInterpolation(originalText, interpolation, isVerbatim);
builder.Add(interp);
}
// Add a token for text following the last interpolation
var lastText = Substring(originalText, interpolations[interpolations.Count - 1].CloseBracePosition + 1, closeQuoteIndex - 1);
if (lastText.Length > 0)
{
var token = MakeStringToken(lastText, lastText, isVerbatim, SyntaxKind.InterpolatedStringTextToken);
builder.Add(SyntaxFactory.InterpolatedStringText(token));
}
}
interpolations.Free();
var result = SyntaxFactory.InterpolatedStringExpression(openQuote, builder, closeQuote);
_pool.Free(builder);
if (error != null)
{
result = result.WithDiagnosticsGreen(new[] { error });
}
Debug.Assert(originalToken.ToFullString() == result.ToFullString()); // yield from text equals yield from node
return(CheckFeatureAvailability(result, MessageID.IDS_FeatureInterpolatedStrings));
}
private ExpressionSyntax ParseInterpolatedStringToken()
{
// We don't want to make the scanner stateful (between tokens) if we can possibly avoid it.
// The approach implemented here is
//
// (1) Scan the whole interpolated string literal as a single token. Now the statefulness of
// the scanner (to match { }'s) is limited to its behavior while scanning a single token.
//
// (2) When the parser gets such a token, here, it spins up another scanner / parser on each of
// the holes and builds a tree for the whole thing (resulting in an InterpolatedStringExpressionSyntax).
//
// (3) The parser discards the original token and replaces it with this tree. (In other words,
// it replaces one token with a different set of tokens that have already been parsed)
//
// (4) On an incremental change, we widen the invalidated region to include any enclosing interpolated
// string nonterminal so that we never reuse tokens inside a changed interpolated string.
//
// This has the secondary advantage that it can reasonably be specified.
//
// The substitution will end up being invisible to external APIs and clients such as the IDE, as
// they have no way to ask for the stream of tokens before parsing.
Debug.Assert(this.CurrentToken.Kind == SyntaxKind.InterpolatedStringToken);
var originalToken = this.EatToken();
var originalText = originalToken.ValueText; // this is actually the source text
Debug.Assert(originalText[0] == '$' || originalText[0] == '@');
// compute the positions of the interpolations in the original string literal, if there was an error or not,
// and where the close quote can be found.
var interpolations = ArrayBuilder <Lexer.Interpolation> .GetInstance();
rescanInterpolation(out var kind, out var error, out var openQuoteRange, interpolations, out var closeQuoteRange);
var result = SyntaxFactory.InterpolatedStringExpression(
getOpenQuote(openQuoteRange), getContent(interpolations), getCloseQuote(closeQuoteRange));
interpolations.Free();
if (error != null)
{
result = result.WithDiagnosticsGreen(new[] { error });
}
Debug.Assert(originalToken.ToFullString() == result.ToFullString()); // yield from text equals yield from node
return(result);
void rescanInterpolation(out Lexer.InterpolatedStringKind kind, out SyntaxDiagnosticInfo error, out Range openQuoteRange, ArrayBuilder <Lexer.Interpolation> interpolations, out Range closeQuoteRange)
{
using var tempLexer = new Lexer(SourceText.From(originalText), this.Options, allowPreprocessorDirectives: false);
var info = default(Lexer.TokenInfo);
tempLexer.ScanInterpolatedStringLiteralTop(ref info, out error, out kind, out openQuoteRange, interpolations, out closeQuoteRange);
}
SyntaxToken getOpenQuote(Range openQuoteRange)
{
var openQuoteText = originalText[openQuoteRange];
return(SyntaxFactory.Token(
originalToken.GetLeadingTrivia(),
kind is Lexer.InterpolatedStringKind.Verbatim ? SyntaxKind.InterpolatedVerbatimStringStartToken : SyntaxKind.InterpolatedStringStartToken,
openQuoteText, openQuoteText, trailing: null));
}
CodeAnalysis.Syntax.InternalSyntax.SyntaxList <InterpolatedStringContentSyntax> getContent(ArrayBuilder <Lexer.Interpolation> interpolations)
{
var builder = _pool.Allocate <InterpolatedStringContentSyntax>();
if (interpolations.Count == 0)
{
// In the special case when there are no interpolations, we just construct a format string
// with no inserts. We must still use String.Format to get its handling of escapes such as {{,
// so we still treat it as a composite format string.
var text = originalText[new Range(openQuoteRange.End, closeQuoteRange.Start)];
if (text.Length > 0)
{
builder.Add(SyntaxFactory.InterpolatedStringText(MakeInterpolatedStringTextToken(text, kind)));
}
}
else
{
for (int i = 0; i < interpolations.Count; i++)
{
var interpolation = interpolations[i];
// Add a token for text preceding the interpolation
var text = originalText[new Range(
i == 0 ? openQuoteRange.End : interpolations[i - 1].CloseBraceRange.End,
interpolation.OpenBraceRange.Start)];
if (text.Length > 0)
{
builder.Add(SyntaxFactory.InterpolatedStringText(MakeInterpolatedStringTextToken(text, kind)));
}
builder.Add(ParseInterpolation(this.Options, originalText, interpolation, kind));
}
// Add a token for text following the last interpolation
var lastText = originalText[new Range(interpolations[^ 1].CloseBraceRange.End, closeQuoteRange.Start)];