<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">I’m not a language/library designer, just a wannabe designer; I’m hitting the limits of my expertise. So unless I lucked out, one of the main designers will have to pick up this ball and clean it up. I’ll be here if you need clarification on stuff.</div><div class=""><br class=""></div><div class="">The seed of this idea was coming up with a equivalent to C++’s “static_assert” after someone querying me about “constexpr” in one of my array threads. Using these expressions during a generic where clause is like using C++ static-assert during template instantiation. Using them during an #if/#elseif/#else surrounding an #error directive (explained in a separate post a couple days ago) acts like using C++ static-asserts in non-template contexts. (This is what inspired the #error proposal.)</div><div class=""><br class=""></div><div class=""><h1 id="toc_0" style="-webkit-print-color-adjust: exact; margin: 0px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 28px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Arbitrary Compiler Constant Expressions</h1><ul style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Proposal: <a href="file:///Users/daryle/NNNN-filename.md" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196); margin-top: 0px;" class="">SE-NNNN</a></li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Authors: <a href="https://github.com/CTMacUser" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196); margin-top: 0px;" class="">Daryle Walker</a>, <a href="https://github.com/swiftdev" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196);" class="">Author 2</a></li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Review Manager: TBD</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Status: <strong style="-webkit-print-color-adjust: exact; margin-top: 0px;" class="">Awaiting review</strong></li></ul><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><em style="-webkit-print-color-adjust: exact;" class="">During the review process, add the following fields as needed:</em></p><ul style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Decision Notes: <a href="https://lists.swift.org/pipermail/swift-evolution/" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196); margin-top: 0px;" class="">Rationale</a>, <a href="https://lists.swift.org/pipermail/swift-evolution/" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196);" class="">Additional Commentary</a></li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Bugs: <a href="https://bugs.swift.org/browse/SR-NNNN" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196); margin-top: 0px;" class="">SR-NNNN</a>, <a href="https://bugs.swift.org/browse/SR-MMMM" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196);" class="">SR-MMMM</a></li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Previous Revision: <a href="https://github.com/apple/swift-evolution/blob/...commit-ID.../proposals/NNNN-filename.md" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196); margin-top: 0px;" class="">1</a></li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Previous Proposal: <a href="file:///Users/daryle/XXXX-filename.md" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196); margin-top: 0px;" class="">SE-XXXX</a></li></ul><h2 id="toc_1" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Introduction</h2><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">This proposal adds compile-time constant expressions, and how to generate them, to the language</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Swift-evolution thread: <a href="https://lists.swift.org/pipermail/swift-evolution/" style="-webkit-print-color-adjust: exact; color: rgb(65, 131, 196);" class="">Discussion thread topic for that proposal</a></p><h2 id="toc_2" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Motivation</h2><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Conditional compilation blocks can shape the design of code based on criteria known at compile time. Generic where clauses do the same for limiting which generics can get instantiated. The criteria for either is extremely limited; Boolean combinations of environment state for conditional compilation blocks, and type equivalence, inheritance, or conformance for generic where clauses.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Other languages, like C++, allow values computed from specially-marked ("<code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">constexpr</code>") objects and functions. Adding this to Swift permits user-side generated tests today, and is a first step to non-Boolean compile-time values, like value-based generic parameters or static-sized array extents.</p><h2 id="toc_3" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Proposed solution</h2><ol style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Define a new declaration attribute that can mark off data and code as being compatible with compile-time expressions (CTE). The definitions of the marked items may have restrictions to ensure realization at compile-time.</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Designate parts of certain constructs that they can only take CTEs. Expressions outside of those constructs are evaluated at run-time as usual.</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Specify the compile-time realization engine.</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Speculate on what parts of the existing standard library should be updated to support CTEs.</li></ol><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">(I have no concrete examples here. But I do think about if we had something like C++'s type-traits library, then we could replace direct type-testing generic where clauses with ones that check the desired traits from our type-traits equivalent structure.)</p><h2 id="toc_4" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Detailed design</h2><h3 id="toc_5" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Computation</h3><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">The language to process the Swift source file for CTEs before compilation is... the compiler itself! The Swift compiler can translate Swift as a compiled language or an interpreted language. CTEs are computed in an interpreted pass of the source code. If the translation is a Swift interpretation, then the translation goes over the CTE directly instead of a second interpreter.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">There cannot be any recursion. If the CTE is within a statement or part of a generic where clause, then the CTE cannot refer either directly or indirectly to the function its modifying. If the CTE is within an initializer, then it cannot refer to the object being initialized. A fatal diagnostic shall be emitted. One shall also be emitted if CTE evaluation reaches a nonreturning function, an uncaught exception, or dereferenced nil optional or similar.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Floating-point operations of the interpreter do not have to exactly match the ones from the compiler. The interpreter will make its best interpolation to a value supported by the compiler.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">The directly-referred symbols of a CTE (the ones seen at the CTE-accepting construct) can only be constant declarations and/or routines that do not have <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">inout</code> parameters or <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">mutating</code> <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">self</code>. Constants have to be literals, top-level objects, or type-level properties. A type-level variable computed property can be used if it's getter-only.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Complier implementations may place restrictions on the complexity, resource usage, time taken, etc., of CTE evaluation. (Put reasonable minimal limits here.)</p><h3 id="toc_6" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Attribute</h3><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">The <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">define</code> attribute shall indicate its owning declaration can be included in CTEs. The corresponding definition must be available through the source code; the attribute is ignored for items with their realization only as binary code.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Such items still have their run-time realization, as if the attribute was never assigned. The attribute can be applied to these declarations:</p><ul style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">constant</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">variable</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">function (including operator definitions and closures)</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">initializer</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">subscript</li></ul><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Constants and variables must be of a CTE-compatible type. Routines must have parameters, returns, and <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">self</code> (if applicable) of a CTE-compatible type. Declarations within a protocol declaration cannot have the attribute, but ones defined in an extension or conforming type can. For methods in an extension for a protocol, the attribute is ignored if the conforming type's implementation methods cannot support it.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">A compile-time expression can be of any type except:</p><ul style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">One without any CTE-compatible initializers</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Tuple types with any non-CTE members</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Static-sized array types (if added) with a non-CTE element type</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">class</code> types</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">struct</code> types with instance-level stored properties of a non-CTE type</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Raw-value <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">enum</code> types with a non-CTE implementation type</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Union <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">enum</code> types with a non-CTE type as an associated value in at least one case</li></ul><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Types can have non-CTE (type-level and/or computed) properties and/or methods with non-CTE parameters/returns; they just can't be accessed/called during a CTE context.</p><h3 id="toc_7" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Minimum Symbol Set Needed to Be CTE-Certified</h3><ul style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Operators and other feasible operations associated with the default Boolean, string/character, and numeric types</li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">The variables and methods of <code style="-webkit-print-color-adjust: exact; margin: 0px 2px; padding: 0px 5px; white-space: nowrap; border: 1px solid rgb(234, 234, 234); background-color: rgb(248, 248, 248); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">MemoryLayout</code></li><li style="-webkit-print-color-adjust: exact; margin: 0px;" class="">(Probably other stuff I haven't considered)</li></ul><h3 id="toc_8" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">CTE Clients</h3><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">CTE can only be used (for now) in conditional compilation blocks and generic where clauses. Since the former currently uses a custom hard-coded Boolean calculus, CTEs will be inserted with a wrapping syntax so the whole dynamic doesn't have to be converted at once.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">For both conditional compilation blocks and generic where clauses, the CTE has to evaluate to a Boolean-compatible type.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Add to the "Grammar of a Conditional Compilation Block":</p><blockquote style="-webkit-print-color-adjust: exact; margin: 15px 0px; border-left-width: 4px; border-left-style: solid; border-left-color: rgb(221, 221, 221); padding: 0px 15px; color: rgb(119, 119, 119); font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><p style="-webkit-print-color-adjust: exact; margin: 0px 0px 15px;" class=""><em style="-webkit-print-color-adjust: exact;" class="">compilation-condition</em> → <strong style="-webkit-print-color-adjust: exact;" class="">inline</strong> <strong style="-webkit-print-color-adjust: exact;" class="">(</strong> <em style="-webkit-print-color-adjust: exact;" class="">compilation-expression</em> <strong style="-webkit-print-color-adjust: exact;" class="">)</strong></p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px 0px;" class=""><em style="-webkit-print-color-adjust: exact;" class="">compilation-expression</em> → <em style="-webkit-print-color-adjust: exact;" class="">expression</em></p></blockquote><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">Add to the "Grammar of a Generic Parameter Clause":</p><blockquote style="-webkit-print-color-adjust: exact; margin: 15px 0px; border-left-width: 4px; border-left-style: solid; border-left-color: rgb(221, 221, 221); padding: 0px 15px; color: rgb(119, 119, 119); font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class=""><div style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><em style="-webkit-print-color-adjust: exact;" class="">requirement</em> → <em style="-webkit-print-color-adjust: exact;" class="">compilation-expression</em></div></blockquote><h2 id="toc_9" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Source compatibility</h2><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">The changes in this proposal should be additive, so existing source should work as-is.</p><h2 id="toc_10" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Effect on ABI stability</h2><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">CTE computation happens at compile-time, so there is no direct effect on the ABI. Generic types and functions from the standard library may change their availability if they take on additional generic where clauses with CTE-based tests.</p><h2 id="toc_11" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Effect on API resilience</h2><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255);" class="">The API would not be affected by this proposal, modulo any changes future standard library authors make to take advantage of complex tests.</p><h2 id="toc_12" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 24px; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(204, 204, 204); font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Alternatives considered</h2><p style="-webkit-print-color-adjust: exact; margin-top: 15px; margin-right: 0px; margin-left: 0px; font-family: Helvetica, arial, sans-serif; font-size: 14px; background-color: rgb(255, 255, 255); margin-bottom: 0px !important;" class="">The main alternative is to do nothing. That would keep conditional compilation blocks and generic where clauses as-is. Value-based generic arguments couldn't be implemented and static-sized arrays would use integer literals and/or custom syntax for their extents list.</p></div><div class=""><br class=""></div><br class=""><div class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">— </div><div class="">Daryle Walker<br class="">Mac, Internet, and Video Game Junkie<br class="">darylew AT mac DOT com </div></div>
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