Substitute type parameters when type checking calls #915
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This was referenced Feb 22, 2024
lars-reimann
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Feb 22, 2024
Related to #915 ### Summary of Changes As described in #915, the code ``` fun f<T>(p: (a: T) -> b: String) pipeline myPipeline { // Expected type '(a: T) -> (b: String)' but got '(a: String) -> (result: String)' f((a: Int) -> a); } ``` currently shows an error due to a parameter mismatch (contravariant context). In a covariant context (e.g. for results), however, no such error is shown. That's because when checking whether a type `T1` can be assigned to a type `T2`, we used to replace a type parameter type as `T1` with its **upper** bound (strict) and as `T2` with its upper bound (lenient). We now instead replace a type parameter as `T1` with its **lower** bound (lenient). This simply checks whether there are any substitutions for `T1` that could let the subtype relation become true.
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This also affects the check for default values of parameters: |
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lars-reimann
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Closes #915 ### Summary of Changes * Substitute type parameter when type checking calls. * Remove lenient type checking mode. We now use the strict mode everywhere, which means when calling `isSubtypeOf(type, other)` that the upper bound of `type` must be a subtype of the lower bound of `other`.
lars-reimann
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## [0.8.0](v0.7.0...v0.8.0) (2024-02-26) ### Features * check the runner version to be compatible ([#888](#888)) ([83378a3](83378a3)), closes [#880](#880) * check type parameter bounds for default values and named types ([#919](#919)) ([7003ea6](7003ea6)), closes [#614](#614) * clamp default values of parameter types to upper bound ([#921](#921)) ([76ad869](76ad869)) * compute highest common subtype ([#901](#901)) ([5630a9f](5630a9f)), closes [#860](#860) * compute type parameters for calls ([#920](#920)) ([35dc826](35dc826)), closes [#861](#861) * consider nullability of upper type parameter bound in various checks ([#892](#892)) ([940515a](940515a)) * constraints for segments ([#911](#911)) ([e57f886](e57f886)), closes [#903](#903) * EDA on pipeline Tables ([#834](#834)) ([f42c9aa](f42c9aa)) * error if parent type is nullable ([#891](#891)) ([add650d](add650d)) * escape characters in string conversion of string constants ([#908](#908)) ([72a9c3c](72a9c3c)), closes [#904](#904) * format upper bound of type parameters ([#898](#898)) ([9d6ce28](9d6ce28)) * handle invariant/covariant type parameters when computing lowest common supertype ([#868](#868)) ([4d6cb4e](4d6cb4e)), closes [#860](#860) [#861](#861) * improve handling of subclasses of lists/maps ([#890](#890)) ([bb0c94b](bb0c94b)) * improvements to constraints ([#896](#896)) ([b81bef9](b81bef9)), closes [#18](#18) [#860](#860) [#18](#18) * include enum name in string conversion of enum variant types ([#907](#907)) ([1f6502e](1f6502e)), closes [#902](#902) * scoping for member accesses if receiver has type parameter type ([#889](#889)) ([1277bd1](1277bd1)) * shorter message if runner is started but files have errors ([#912](#912)) ([b611b44](b611b44)), closes [#910](#910) * simplify union types containing type parameter types disregarding entry order ([#894](#894)) ([cf6e77e](cf6e77e)) * singular type is its own lowest common supertype ([#893](#893)) ([79d611d](79d611d)) * substitute type parameter when type checking calls ([#923](#923)) ([2e09306](2e09306)), closes [#915](#915) * substitute type parameters when checking overridden members ([#922](#922)) ([0e657cf](0e657cf)), closes [#917](#917) * update to `safe-ds-runner` v0.7.0 ([#906](#906)) ([070f406](070f406)) * use bounds of type system where possible ([#899](#899)) ([cf92762](cf92762)) ### Bug Fixes * lenient type checking involving type parameter types ([#916](#916)) ([b9d3641](b9d3641)), closes [#915](#915) [#915](#915) * runner startup silent failure ([#914](#914)) ([8812944](8812944)), closes [#909](#909) * save dirty files before running pipeline ([#918](#918)) ([4302ca6](4302ca6)) * simplification of union types ([#897](#897)) ([4c577a3](4c577a3))
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🎉 This issue has been resolved in version 0.8.0 🎉 The release is available on: Your semantic-release bot 📦🚀 |
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Is your feature request related to a problem?
For calls of functions with type parameters, the type checker might show incorrect errors:
That's because
Thas the upper boundAny?and, thus,Stringis not generally a supertype ofT(comparing the parameter types).Desired solution
Once #861 is done, we also need to substitute type parameters when checking argument types vs. parameter types. Since we need these substitutions multiple times (for each parameter and for the call results in #861), we might also consider caching the substitutions for each call.
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