[hamid-digitalmarketer]

Summary

Fixes #407

Problem

When calling unit methods on container aliases that fix their error type to Exception (e.g. IOResultE.from_value(1), ResultE.from_value(1), FutureResultE.from_value(1)), mypy previously typed the return value as Container[ValueType, Any] rather than Container[ValueType, Exception], because the generic unit constructor cannot infer the unprovided error type parameter and defaults to Any.

Solution

• Introduced returns.contrib.mypy._features.alias_e.analyze method hook for unit constructor methods across all *E aliases (ResultE, IOResultE, FutureResultE, RequiresContextResultE, RequiresContextIOResultE, RequiresContextFutureResultE).
• When the constructor is invoked via an *E alias whose bound type fixes the error type to builtins.Exception, any AnyType in that position is rewritten to builtins.Exception.
• Direct constructor calls on the un-aliased base containers (e.g. IOResult.from_value(1)) are unaffected and retain their default Any error type.

Verification

• Added test cases in typesafety/test_io/test_ioresult_container/test_ioresult_typecast.yml.
• Verified type resolution across all *E containers:

  reveal_type(IOResultE.from_value(1))  # => returns.io.IOResult[int, Exception]
  reveal_type(ResultE.from_value(1))    # => returns.result.Result[int, Exception]
  reveal_type(FutureResultE.from_value(1)) # => returns.future.FutureResult[int, Exception]
  reveal_type(IOResult.from_value(1))   # => returns.io.IOResult[int, Any] (preserved)

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[codspeed]

Merging this PR will not alter performance

1 note

ℹ️ 2 benchmarks have no flamegraph

The flamegraph wasn't generated: the symbols of the profiling trace could not be resolved, because no information about the language frames was collected.

See affected benchmarks

✅ 22 untouched benchmarks

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_{Comparing hamid-digitalmarketer:fix/issue-407-e-alias-unit-methods (5cc6eb9) with master (ea76fb5)}