Add inference for t-strings - #3120
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A t-string is now inferred as an instance of string.templatelib.Template, and an interpolation field as an instance of string.templatelib.Interpolation, rather than raising or inferring as str (unlike f-strings / JoinedStr). The Template/Interpolation members are reconstructed from the actual template contents, mirroring the PEP 750 runtime semantics: Template.strings/values/interpolations and Interpolation.value/expression/conversion/format_spec infer to the same values produced at runtime. This is implemented with dedicated TemplateStrInstance / InterpolationInstance objects backed by TemplateStrModel / InterpolationModel object models, in the same way DictInstance/ExceptionInstance expose synthetic members. The standard library defines Template and Interpolation via type(t"..."), which is not statically inferable. A new brain plugin (brain_string) rebuilds the real classes from the live objects via InspectBuilder, so they resolve to ClassDef nodes with the genuine PEP 750 API instead of a hand-written stub. Also fix as_string for TemplateStr to double literal braces and use repr-based escaping in the constant parts, mirroring JoinedStr, so the rendered code round-trips. Closes #2789
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #3120 +/- ##
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+ Coverage 93.67% 93.74% +0.07%
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Files 93 94 +1
Lines 11645 11760 +115
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+ Hits 10908 11024 +116
+ Misses 737 736 -1
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The generator pauses at yield util.Uninferable, so the tests exhaust it with list() to also execute the return lines. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Type of Changes
Description
A t-string is now inferred as an instance of
string.templatelib.Template, and an interpolation field as an instance of string.templatelib.Interpolation, rather than raising or inferring as str (unlike f-strings / JoinedStr).
The Template/Interpolation members are reconstructed from the actual template contents, mirroring the PEP 750 runtime semantics: Template.strings/values/interpolations and
Interpolation.value/expression/conversion/format_spec infer to the same values produced at runtime. This is implemented with dedicated TemplateStrInstance / InterpolationInstance objects backed by TemplateStrModel / InterpolationModel object models, in the same way DictInstance/ExceptionInstance expose synthetic members.
The standard library defines Template and Interpolation via type(t"..."), which is not statically inferable. A new brain plugin (brain_string) rebuilds the real classes from the live objects via InspectBuilder, so they resolve to ClassDef nodes with the genuine PEP 750 API instead of a hand-written stub.
Also fix as_string for TemplateStr to double literal braces and use repr-based escaping in the constant parts, mirroring JoinedStr, so the rendered code round-trips.
Closes #2789