Feature: string interpolation

[fibodevy]

string interpolation

• Source: feat/strinterp
• Docs: feat/strinterp/unleashed/docs/string-interpolation.md

Embed expressions straight into a string literal with $'...' and {}:

writeln($'Hello {name}, you are {age} years old');
writeln($'Pi = {Pi:0.00}, n = {n:x4}, today = {Now:yyyy-mm-dd}');

{expr} auto-formats by type: scalars pass through WriteStr, class instances call ToString, class refs give the name, arrays unroll into [a, b, c]. {expr:mask} routes to Format / FormatDateTime / FormatFloat / IntToHex depending on the type and the mask shape. Masks default to the invariant locale; an L prefix opts into the system one.

Heads up on a recent change

The format spec used to be {expr as 'mask'}. It's now {expr:mask} - the mask is the raw text after the colon, no quotes, no escaping. Reads closer to C#/Python and lets as keep its normal meaning inside {}. Full dispatch table and the rest is in the docs.

IDE

The IDE side is ready too on feat/strinterp: SynEdit highlights $'...' literals and colours the :mask as part of the string, and CodeTools knows the syntax so rename / find-references reach identifiers inside {} and skip past the mask.

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This is about ready to merge. If you have any objections or want changes, now is the moment - raise concerns and request changes before it goes in.