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| <ol class="chapter"><li class="chapter-item affix "><a href="../index.html">Introduction</a></li><li class="chapter-item "><a href="../hello.html"><strong aria-hidden="true">1.</strong> Hello World</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../hello/comment.html"><strong aria-hidden="true">1.1.</strong> Comments</a></li><li class="chapter-item "><a href="../hello/print.html"><strong aria-hidden="true">1.2.</strong> Formatted print</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../hello/print/print_debug.html"><strong aria-hidden="true">1.2.1.</strong> Debug</a></li><li class="chapter-item "><a href="../hello/print/print_display.html"><strong aria-hidden="true">1.2.2.</strong> Display</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../hello/print/print_display/testcase_list.html"><strong aria-hidden="true">1.2.2.1.</strong> Testcase: List</a></li></ol></li><li class="chapter-item "><a href="../hello/print/fmt.html"><strong aria-hidden="true">1.2.3.</strong> Formatting</a></li></ol></li></ol></li><li class="chapter-item "><a href="../primitives.html"><strong aria-hidden="true">2.</strong> Primitives</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../primitives/literals.html"><strong aria-hidden="true">2.1.</strong> Literals and operators</a></li><li class="chapter-item "><a href="../primitives/tuples.html"><strong aria-hidden="true">2.2.</strong> Tuples</a></li><li class="chapter-item "><a href="../primitives/array.html"><strong aria-hidden="true">2.3.</strong> Arrays and Slices</a></li></ol></li><li class="chapter-item "><a href="../custom_types.html"><strong aria-hidden="true">3.</strong> Custom Types</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../custom_types/structs.html"><strong aria-hidden="true">3.1.</strong> Structures</a></li><li class="chapter-item "><a href="../custom_types/enum.html"><strong aria-hidden="true">3.2.</strong> Enums</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../custom_types/enum/enum_use.html"><strong aria-hidden="true">3.2.1.</strong> use</a></li><li class="chapter-item "><a href="../custom_types/enum/c_like.html"><strong aria-hidden="true">3.2.2.</strong> C-like</a></li><li class="chapter-item "><a href="../custom_types/enum/testcase_linked_list.html"><strong aria-hidden="true">3.2.3.</strong> Testcase: linked-list</a></li></ol></li><li class="chapter-item "><a href="../custom_types/constants.html"><strong aria-hidden="true">3.3.</strong> constants</a></li></ol></li><li class="chapter-item "><a href="../variable_bindings.html"><strong aria-hidden="true">4.</strong> Variable Bindings</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../variable_bindings/mut.html"><strong aria-hidden="true">4.1.</strong> Mutability</a></li><li class="chapter-item "><a href="../variable_bindings/scope.html"><strong aria-hidden="true">4.2.</strong> Scope and Shadowing</a></li><li class="chapter-item "><a href="../variable_bindings/declare.html"><strong aria-hidden="true">4.3.</strong> Declare first</a></li><li class="chapter-item "><a href="../variable_bindings/freeze.html"><strong aria-hidden="true">4.4.</strong> Freezing</a></li></ol></li><li class="chapter-item "><a href="../types.html"><strong aria-hidden="true">5.</strong> Types</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../types/cast.html"><strong aria-hidden="true">5.1.</strong> Casting</a></li><li class="chapter-item "><a href="../types/literals.html"><strong aria-hidden="true">5.2.</strong> Literals</a></li><li class="chapter-item "><a href="../types/inference.html"><strong aria-hidden="true">5.3.</strong> Inference</a></li><li class="chapter-item "><a href="../types/alias.html"><strong aria-hidden="true">5.4.</strong> Aliasing</a></li></ol></li><li class="chapter-item "><a href="../conversion.html"><strong aria-hidden="true">6.</strong> Conversion</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../conversion/from_into.html"><strong aria-hidden="true">6.1.</strong> From and Into</a></li><li class="chapter-item "><a href="../conversion/try_from_try_into.html"><strong aria-hidden="true">6.2.</strong> TryFrom and TryInto</a></li><li class="chapter-item "><a href="../conversion/string.html"><strong aria-hidden="true">6.3.</strong> To and from Strings</a></li></ol></li><li class="chapter-item "><a href="../expression.html"><strong aria-hidden="true">7.</strong> Expressions</a></li><li class="chapter-item "><a href="../flow_control.html"><strong aria-hidden="true">8.</strong> Flow of Control</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../flow_control/if_else.html"><strong aria-hidden="true">8.1.</strong> if/else</a></li><li class="chapter-item "><a href="../flow_control/loop.html"><strong aria-hidden="true">8.2.</strong> loop</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../flow_control/loop/nested.html"><strong aria-hidden="true">8.2.1.</strong> Nesting and labels</a></li><li class="chapter-item "><a href="../flow_control/loop/return.html"><strong aria-hidden="true">8.2.2.</strong> Returning from loops</a></li></ol></li><li class="chapter-item "><a href="../flow_control/while.html"><strong aria-hidden="true">8.3.</strong> while</a></li><li class="chapter-item "><a href="../flow_control/for.html"><strong aria-hidden="true">8.4.</strong> for and range</a></li><li class="chapter-item "><a href="../flow_control/match.html"><strong aria-hidden="true">8.5.</strong> match</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../flow_control/match/destructuring.html"><strong aria-hidden="true">8.5.1.</strong> Destructuring</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../flow_control/match/destructuring/destructure_tuple.html"><strong aria-hidden="true">8.5.1.1.</strong> tuples</a></li><li class="chapter-item "><a href="../flow_control/match/destructuring/destructure_enum.html"><strong aria-hidden="true">8.5.1.2.</strong> enums</a></li><li class="chapter-item "><a href="../flow_control/match/destructuring/destructure_pointers.html"><strong aria-hidden="true">8.5.1.3.</strong> pointers/ref</a></li><li class="chapter-item "><a href="../flow_control/match/destructuring/destructure_structures.html"><strong aria-hidden="true">8.5.1.4.</strong> structs</a></li></ol></li><li class="chapter-item "><a href="../flow_control/match/guard.html"><strong aria-hidden="true">8.5.2.</strong> Guards</a></li><li class="chapter-item "><a href="../flow_control/match/binding.html"><strong aria-hidden="true">8.5.3.</strong> Binding</a></li></ol></li><li class="chapter-item "><a href="../flow_control/if_let.html"><strong aria-hidden="true">8.6.</strong> if let</a></li><li class="chapter-item "><a href="../flow_control/while_let.html"><strong aria-hidden="true">8.7.</strong> while let</a></li></ol></li><li class="chapter-item "><a href="../fn.html"><strong aria-hidden="true">9.</strong> Functions</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../fn/methods.html"><strong aria-hidden="true">9.1.</strong> Methods</a></li><li class="chapter-item "><a href="../fn/closures.html"><strong aria-hidden="true">9.2.</strong> Closures</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../fn/closures/capture.html"><strong aria-hidden="true">9.2.1.</strong> Capturing</a></li><li class="chapter-item "><a href="../fn/closures/input_parameters.html"><strong aria-hidden="true">9.2.2.</strong> As input parameters</a></li><li class="chapter-item "><a href="../fn/closures/anonymity.html"><strong aria-hidden="true">9.2.3.</strong> Type anonymity</a></li><li class="chapter-item "><a href="../fn/closures/input_functions.html"><strong aria-hidden="true">9.2.4.</strong> Input functions</a></li><li class="chapter-item "><a href="../fn/closures/output_parameters.html"><strong aria-hidden="true">9.2.5.</strong> As output parameters</a></li><li class="chapter-item "><a href="../fn/closures/closure_examples.html"><strong aria-hidden="true">9.2.6.</strong> Examples in std</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../fn/closures/closure_examples/iter_any.html"><strong aria-hidden="true">9.2.6.1.</strong> Iterator::any</a></li><li class="chapter-item "><a href="../fn/closures/closure_examples/iter_find.html"><strong aria-hidden="true">9.2.6.2.</strong> Searching through iterators</a></li></ol></li></ol></li><li class="chapter-item "><a href="../fn/hof.html"><strong aria-hidden="true">9.3.</strong> Higher Order Functions</a></li><li class="chapter-item "><a href="../fn/diverging.html"><strong aria-hidden="true">9.4.</strong> Diverging functions</a></li></ol></li><li class="chapter-item "><a href="../mod.html"><strong aria-hidden="true">10.</strong> Modules</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../mod/visibility.html"><strong aria-hidden="true">10.1.</strong> Visibility</a></li><li class="chapter-item "><a href="../mod/struct_visibility.html"><strong aria-hidden="true">10.2.</strong> Struct visibility</a></li><li class="chapter-item "><a href="../mod/use.html"><strong aria-hidden="true">10.3.</strong> The use declaration</a></li><li class="chapter-item "><a href="../mod/super.html"><strong aria-hidden="true">10.4.</strong> super and self</a></li><li class="chapter-item "><a href="../mod/split.html"><strong aria-hidden="true">10.5.</strong> File hierarchy</a></li></ol></li><li class="chapter-item "><a href="../crates.html"><strong aria-hidden="true">11.</strong> Crates</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../crates/lib.html"><strong aria-hidden="true">11.1.</strong> Creating a Library</a></li><li class="chapter-item "><a href="../crates/using_lib.html"><strong aria-hidden="true">11.2.</strong> Using a Library</a></li></ol></li><li class="chapter-item "><a href="../cargo.html"><strong aria-hidden="true">12.</strong> Cargo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/deps.html"><strong aria-hidden="true">12.1.</strong> Dependencies</a></li><li class="chapter-item "><a href="../cargo/conventions.html"><strong aria-hidden="true">12.2.</strong> Conventions</a></li><li class="chapter-item "><a href="../cargo/test.html"><strong aria-hidden="true">12.3.</strong> Tests</a></li><li class="chapter-item "><a href="../cargo/build_scripts.html"><strong aria-hidden="true">12.4.</strong> Build Scripts</a></li></ol></li><li class="chapter-item "><a href="../attribute.html"><strong aria-hidden="true">13.</strong> Attributes</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../attribute/unused.html"><strong aria-hidden="true">13.1.</strong> dead_code</a></li><li class="chapter-item "><a href="../attribute/crate.html"><strong aria-hidden="true">13.2.</strong> Crates</a></li><li class="chapter-item "><a href="../attribute/cfg.html"><strong aria-hidden="true">13.3.</strong> cfg</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../attribute/cfg/custom.html"><strong aria-hidden="true">13.3.1.</strong> Custom</a></li></ol></li></ol></li><li class="chapter-item "><a href="../generics.html"><strong aria-hidden="true">14.</strong> Generics</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../generics/gen_fn.html"><strong aria-hidden="true">14.1.</strong> Functions</a></li><li class="chapter-item "><a href="../generics/impl.html"><strong aria-hidden="true">14.2.</strong> Implementation</a></li><li class="chapter-item "><a href="../generics/gen_trait.html"><strong aria-hidden="true">14.3.</strong> Traits</a></li><li class="chapter-item "><a href="../generics/bounds.html"><strong aria-hidden="true">14.4.</strong> Bounds</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../generics/bounds/testcase_empty.html"><strong aria-hidden="true">14.4.1.</strong> Testcase: empty bounds</a></li></ol></li><li class="chapter-item "><a href="../generics/multi_bounds.html"><strong aria-hidden="true">14.5.</strong> Multiple bounds</a></li><li class="chapter-item "><a href="../generics/where.html"><strong aria-hidden="true">14.6.</strong> Where clauses</a></li><li class="chapter-item "><a href="../generics/new_types.html"><strong aria-hidden="true">14.7.</strong> New Type Idiom</a></li><li class="chapter-item "><a href="../generics/assoc_items.html"><strong aria-hidden="true">14.8.</strong> Associated items</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../generics/assoc_items/the_problem.html"><strong aria-hidden="true">14.8.1.</strong> The Problem</a></li><li class="chapter-item "><a href="../generics/assoc_items/types.html"><strong aria-hidden="true">14.8.2.</strong> Associated types</a></li></ol></li><li class="chapter-item "><a href="../generics/phantom.html"><strong aria-hidden="true">14.9.</strong> Phantom type parameters</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../generics/phantom/testcase_units.html"><strong aria-hidden="true">14.9.1.</strong> Testcase: unit clarification</a></li></ol></li></ol></li><li class="chapter-item "><a href="../scope.html"><strong aria-hidden="true">15.</strong> Scoping rules</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../scope/raii.html"><strong aria-hidden="true">15.1.</strong> RAII</a></li><li class="chapter-item "><a href="../scope/move.html"><strong aria-hidden="true">15.2.</strong> Ownership and moves</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../scope/move/mut.html"><strong aria-hidden="true">15.2.1.</strong> Mutability</a></li><li class="chapter-item "><a href="../scope/move/partial_move.html"><strong aria-hidden="true">15.2.2.</strong> Partial moves</a></li></ol></li><li class="chapter-item "><a href="../scope/borrow.html"><strong aria-hidden="true">15.3.</strong> Borrowing</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../scope/borrow/mut.html"><strong aria-hidden="true">15.3.1.</strong> Mutability</a></li><li class="chapter-item "><a href="../scope/borrow/alias.html"><strong aria-hidden="true">15.3.2.</strong> Aliasing</a></li><li class="chapter-item "><a href="../scope/borrow/ref.html"><strong aria-hidden="true">15.3.3.</strong> The ref pattern</a></li></ol></li><li class="chapter-item "><a href="../scope/lifetime.html"><strong aria-hidden="true">15.4.</strong> Lifetimes</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../scope/lifetime/explicit.html"><strong aria-hidden="true">15.4.1.</strong> Explicit annotation</a></li><li class="chapter-item "><a href="../scope/lifetime/fn.html"><strong aria-hidden="true">15.4.2.</strong> Functions</a></li><li class="chapter-item "><a href="../scope/lifetime/methods.html"><strong aria-hidden="true">15.4.3.</strong> Methods</a></li><li class="chapter-item "><a href="../scope/lifetime/struct.html"><strong aria-hidden="true">15.4.4.</strong> Structs</a></li><li class="chapter-item "><a href="../scope/lifetime/trait.html"><strong aria-hidden="true">15.4.5.</strong> Traits</a></li><li class="chapter-item "><a href="../scope/lifetime/lifetime_bounds.html"><strong aria-hidden="true">15.4.6.</strong> Bounds</a></li><li class="chapter-item "><a href="../scope/lifetime/lifetime_coercion.html"><strong aria-hidden="true">15.4.7.</strong> Coercion</a></li><li class="chapter-item "><a href="../scope/lifetime/static_lifetime.html"><strong aria-hidden="true">15.4.8.</strong> Static</a></li><li class="chapter-item "><a href="../scope/lifetime/elision.html"><strong aria-hidden="true">15.4.9.</strong> Elision</a></li></ol></li></ol></li><li class="chapter-item "><a href="../trait.html"><strong aria-hidden="true">16.</strong> Traits</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../trait/derive.html"><strong aria-hidden="true">16.1.</strong> Derive</a></li><li class="chapter-item "><a href="../trait/dyn.html"><strong aria-hidden="true">16.2.</strong> Returning Traits with dyn</a></li><li class="chapter-item "><a href="../trait/ops.html"><strong aria-hidden="true">16.3.</strong> Operator Overloading</a></li><li class="chapter-item "><a href="../trait/drop.html"><strong aria-hidden="true">16.4.</strong> Drop</a></li><li class="chapter-item "><a href="../trait/iter.html"><strong aria-hidden="true">16.5.</strong> Iterators</a></li><li class="chapter-item "><a href="../trait/impl_trait.html"><strong aria-hidden="true">16.6.</strong> impl Trait</a></li><li class="chapter-item "><a href="../trait/clone.html"><strong aria-hidden="true">16.7.</strong> Clone</a></li><li class="chapter-item "><a href="../trait/supertraits.html"><strong aria-hidden="true">16.8.</strong> Supertraits</a></li><li class="chapter-item "><a href="../trait/disambiguating.html"><strong aria-hidden="true">16.9.</strong> Disambiguating overlapping traits</a></li></ol></li><li class="chapter-item "><a href="../macros.html"><strong aria-hidden="true">17.</strong> macro_rules!</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../macros/syntax.html"><strong aria-hidden="true">17.1.</strong> Syntax</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../macros/designators.html"><strong aria-hidden="true">17.1.1.</strong> Designators</a></li><li class="chapter-item "><a href="../macros/overload.html"><strong aria-hidden="true">17.1.2.</strong> Overload</a></li><li class="chapter-item "><a href="../macros/repeat.html"><strong aria-hidden="true">17.1.3.</strong> Repeat</a></li></ol></li><li class="chapter-item "><a href="../macros/dry.html"><strong aria-hidden="true">17.2.</strong> DRY (Don't Repeat Yourself)</a></li><li class="chapter-item "><a href="../macros/dsl.html"><strong aria-hidden="true">17.3.</strong> DSL (Domain Specific Languages)</a></li><li class="chapter-item "><a href="../macros/variadics.html"><strong aria-hidden="true">17.4.</strong> Variadics</a></li></ol></li><li class="chapter-item "><a href="../error.html"><strong aria-hidden="true">18.</strong> Error handling</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../error/panic.html"><strong aria-hidden="true">18.1.</strong> panic</a></li><li class="chapter-item "><a href="../error/option_unwrap.html"><strong aria-hidden="true">18.2.</strong> Option & unwrap</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../error/option_unwrap/question_mark.html"><strong aria-hidden="true">18.2.1.</strong> Unpacking options with ?</a></li><li class="chapter-item "><a href="../error/option_unwrap/map.html"><strong aria-hidden="true">18.2.2.</strong> Combinators: map</a></li><li class="chapter-item "><a href="../error/option_unwrap/and_then.html"><strong aria-hidden="true">18.2.3.</strong> Combinators: and_then</a></li></ol></li><li class="chapter-item "><a href="../error/result.html"><strong aria-hidden="true">18.3.</strong> Result</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../error/result/result_map.html"><strong aria-hidden="true">18.3.1.</strong> map for Result</a></li><li class="chapter-item "><a href="../error/result/result_alias.html"><strong aria-hidden="true">18.3.2.</strong> aliases for Result</a></li><li class="chapter-item "><a href="../error/result/early_returns.html"><strong aria-hidden="true">18.3.3.</strong> Early returns</a></li><li class="chapter-item "><a href="../error/result/enter_question_mark.html"><strong aria-hidden="true">18.3.4.</strong> Introducing ?</a></li></ol></li><li class="chapter-item "><a href="../error/multiple_error_types.html"><strong aria-hidden="true">18.4.</strong> Multiple error types</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../error/multiple_error_types/option_result.html"><strong aria-hidden="true">18.4.1.</strong> Pulling Results out of Options</a></li><li class="chapter-item "><a href="../error/multiple_error_types/define_error_type.html"><strong aria-hidden="true">18.4.2.</strong> Defining an error type</a></li><li class="chapter-item "><a href="../error/multiple_error_types/boxing_errors.html"><strong aria-hidden="true">18.4.3.</strong> Boxing errors</a></li><li class="chapter-item "><a href="../error/multiple_error_types/reenter_question_mark.html"><strong aria-hidden="true">18.4.4.</strong> Other uses of ?</a></li><li class="chapter-item "><a href="../error/multiple_error_types/wrap_error.html"><strong aria-hidden="true">18.4.5.</strong> Wrapping errors</a></li></ol></li><li class="chapter-item "><a href="../error/iter_result.html"><strong aria-hidden="true">18.5.</strong> Iterating over Results</a></li></ol></li><li class="chapter-item "><a href="../std.html"><strong aria-hidden="true">19.</strong> Std library types</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../std/box.html"><strong aria-hidden="true">19.1.</strong> Box, stack and heap</a></li><li class="chapter-item "><a href="../std/vec.html"><strong aria-hidden="true">19.2.</strong> Vectors</a></li><li class="chapter-item "><a href="../std/str.html"><strong aria-hidden="true">19.3.</strong> Strings</a></li><li class="chapter-item "><a href="../std/option.html"><strong aria-hidden="true">19.4.</strong> Option</a></li><li class="chapter-item "><a href="../std/result.html"><strong aria-hidden="true">19.5.</strong> Result</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../std/result/question_mark.html"><strong aria-hidden="true">19.5.1.</strong> ?</a></li></ol></li><li class="chapter-item "><a href="../std/panic.html"><strong aria-hidden="true">19.6.</strong> panic!</a></li><li class="chapter-item "><a href="../std/hash.html"><strong aria-hidden="true">19.7.</strong> HashMap</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../std/hash/alt_key_types.html"><strong aria-hidden="true">19.7.1.</strong> Alternate/custom key types</a></li><li class="chapter-item "><a href="../std/hash/hashset.html"><strong aria-hidden="true">19.7.2.</strong> HashSet</a></li></ol></li><li class="chapter-item "><a href="../std/rc.html"><strong aria-hidden="true">19.8.</strong> Rc</a></li><li class="chapter-item "><a href="../std/arc.html"><strong aria-hidden="true">19.9.</strong> Arc</a></li></ol></li><li class="chapter-item "><a href="../std_misc.html"><strong aria-hidden="true">20.</strong> Std misc</a><a 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href="../std_misc/file/create.html"><strong aria-hidden="true">20.4.2.</strong> create</a></li><li class="chapter-item "><a href="../std_misc/file/read_lines.html"><strong aria-hidden="true">20.4.3.</strong> read lines</a></li></ol></li><li class="chapter-item "><a href="../std_misc/process.html"><strong aria-hidden="true">20.5.</strong> Child processes</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../std_misc/process/pipe.html"><strong aria-hidden="true">20.5.1.</strong> Pipes</a></li><li class="chapter-item "><a href="../std_misc/process/wait.html"><strong aria-hidden="true">20.5.2.</strong> Wait</a></li></ol></li><li class="chapter-item "><a href="../std_misc/fs.html"><strong aria-hidden="true">20.6.</strong> Filesystem Operations</a></li><li class="chapter-item "><a href="../std_misc/arg.html"><strong aria-hidden="true">20.7.</strong> Program arguments</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../std_misc/arg/matching.html"><strong aria-hidden="true">20.7.1.</strong> Argument parsing</a></li></ol></li><li class="chapter-item "><a href="../std_misc/ffi.html"><strong aria-hidden="true">20.8.</strong> Foreign Function Interface</a></li></ol></li><li class="chapter-item expanded "><a href="../testing.html"><strong aria-hidden="true">21.</strong> Testing</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../testing/unit_testing.html" class="active"><strong aria-hidden="true">21.1.</strong> Unit testing</a></li><li class="chapter-item "><a href="../testing/doc_testing.html"><strong aria-hidden="true">21.2.</strong> Documentation testing</a></li><li class="chapter-item "><a href="../testing/integration_testing.html"><strong aria-hidden="true">21.3.</strong> Integration testing</a></li><li class="chapter-item "><a href="../testing/dev_dependencies.html"><strong aria-hidden="true">21.4.</strong> Dev-dependencies</a></li></ol></li><li class="chapter-item "><a href="../unsafe.html"><strong aria-hidden="true">22.</strong> Unsafe Operations</a></li><li class="chapter-item "><a href="../compatibility.html"><strong aria-hidden="true">23.</strong> Compatibility</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compatibility/raw_identifiers.html"><strong aria-hidden="true">23.1.</strong> Raw identifiers</a></li></ol></li><li class="chapter-item "><a href="../meta.html"><strong aria-hidden="true">24.</strong> Meta</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../meta/doc.html"><strong aria-hidden="true">24.1.</strong> Documentation</a></li><li class="chapter-item "><a href="../meta/playpen.html"><strong aria-hidden="true">24.2.</strong> Playpen</a></li></ol></li></ol> |
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| <h1 class="menu-title">Rust By Example</h1> |
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| <main> |
| <h1 id="unit-testing"><a class="header" href="#unit-testing">Unit testing</a></h1> |
| <p>Tests are Rust functions that verify that the non-test code is functioning in |
| the expected manner. The bodies of test functions typically perform some setup, |
| run the code we want to test, then assert whether the results are what we |
| expect.</p> |
| <p>Most unit tests go into a <code>tests</code> <a href="../mod.html">mod</a> with the <code>#[cfg(test)]</code> <a href="../attribute.html">attribute</a>. |
| Test functions are marked with the <code>#[test]</code> attribute.</p> |
| <p>Tests fail when something in the test function <a href="../std/panic.html">panics</a>. There are some |
| helper <a href="../macros.html">macros</a>:</p> |
| <ul> |
| <li><code>assert!(expression)</code> - panics if expression evaluates to <code>false</code>.</li> |
| <li><code>assert_eq!(left, right)</code> and <code>assert_ne!(left, right)</code> - testing left and |
| right expressions for equality and inequality respectively.</li> |
| </ul> |
| <pre><code class="language-rust ignore">pub fn add(a: i32, b: i32) -> i32 { |
| a + b |
| } |
| |
| // This is a really bad adding function, its purpose is to fail in this |
| // example. |
| #[allow(dead_code)] |
| fn bad_add(a: i32, b: i32) -> i32 { |
| a - b |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| // Note this useful idiom: importing names from outer (for mod tests) scope. |
| use super::*; |
| |
| #[test] |
| fn test_add() { |
| assert_eq!(add(1, 2), 3); |
| } |
| |
| #[test] |
| fn test_bad_add() { |
| // This assert would fire and test will fail. |
| // Please note, that private functions can be tested too! |
| assert_eq!(bad_add(1, 2), 3); |
| } |
| } |
| </code></pre> |
| <p>Tests can be run with <code>cargo test</code>.</p> |
| <pre><code class="language-shell">$ cargo test |
| |
| running 2 tests |
| test tests::test_bad_add ... FAILED |
| test tests::test_add ... ok |
| |
| failures: |
| |
| ---- tests::test_bad_add stdout ---- |
| thread 'tests::test_bad_add' panicked at 'assertion failed: `(left == right)` |
| left: `-1`, |
| right: `3`', src/lib.rs:21:8 |
| note: Run with `RUST_BACKTRACE=1` for a backtrace. |
| |
| |
| failures: |
| tests::test_bad_add |
| |
| test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out |
| </code></pre> |
| <h2 id="tests-and-"><a class="header" href="#tests-and-">Tests and <code>?</code></a></h2> |
| <p>None of the previous unit test examples had a return type. But in Rust 2018, |
| your unit tests can return <code>Result<()></code>, which lets you use <code>?</code> in them! This |
| can make them much more concise.</p> |
| <pre><pre class="playground"><code class="language-rust editable">fn sqrt(number: f64) -> Result<f64, String> { |
| if number >= 0.0 { |
| Ok(number.powf(0.5)) |
| } else { |
| Err("negative floats don't have square roots".to_owned()) |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| #[test] |
| fn test_sqrt() -> Result<(), String> { |
| let x = 4.0; |
| assert_eq!(sqrt(x)?.powf(2.0), x); |
| Ok(()) |
| } |
| } |
| </code></pre></pre> |
| <p>See <a href="https://doc.rust-lang.org/edition-guide/rust-2018/error-handling-and-panics/question-mark-in-main-and-tests.html">"The Edition Guide"</a> for more details.</p> |
| <h2 id="testing-panics"><a class="header" href="#testing-panics">Testing panics</a></h2> |
| <p>To check functions that should panic under certain circumstances, use attribute |
| <code>#[should_panic]</code>. This attribute accepts optional parameter <code>expected = </code> with |
| the text of the panic message. If your function can panic in multiple ways, it helps |
| make sure your test is testing the correct panic.</p> |
| <pre><code class="language-rust ignore">pub fn divide_non_zero_result(a: u32, b: u32) -> u32 { |
| if b == 0 { |
| panic!("Divide-by-zero error"); |
| } else if a < b { |
| panic!("Divide result is zero"); |
| } |
| a / b |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| #[test] |
| fn test_divide() { |
| assert_eq!(divide_non_zero_result(10, 2), 5); |
| } |
| |
| #[test] |
| #[should_panic] |
| fn test_any_panic() { |
| divide_non_zero_result(1, 0); |
| } |
| |
| #[test] |
| #[should_panic(expected = "Divide result is zero")] |
| fn test_specific_panic() { |
| divide_non_zero_result(1, 10); |
| } |
| } |
| </code></pre> |
| <p>Running these tests gives us:</p> |
| <pre><code class="language-shell">$ cargo test |
| |
| running 3 tests |
| test tests::test_any_panic ... ok |
| test tests::test_divide ... ok |
| test tests::test_specific_panic ... ok |
| |
| test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| |
| Doc-tests tmp-test-should-panic |
| |
| running 0 tests |
| |
| test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| </code></pre> |
| <h2 id="running-specific-tests"><a class="header" href="#running-specific-tests">Running specific tests</a></h2> |
| <p>To run specific tests one may specify the test name to <code>cargo test</code> command.</p> |
| <pre><code class="language-shell">$ cargo test test_any_panic |
| running 1 test |
| test tests::test_any_panic ... ok |
| |
| test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 2 filtered out |
| |
| Doc-tests tmp-test-should-panic |
| |
| running 0 tests |
| |
| test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| </code></pre> |
| <p>To run multiple tests one may specify part of a test name that matches all the |
| tests that should be run.</p> |
| <pre><code class="language-shell">$ cargo test panic |
| running 2 tests |
| test tests::test_any_panic ... ok |
| test tests::test_specific_panic ... ok |
| |
| test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out |
| |
| Doc-tests tmp-test-should-panic |
| |
| running 0 tests |
| |
| test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| </code></pre> |
| <h2 id="ignoring-tests"><a class="header" href="#ignoring-tests">Ignoring tests</a></h2> |
| <p>Tests can be marked with the <code>#[ignore]</code> attribute to exclude some tests. Or to run |
| them with command <code>cargo test -- --ignored</code></p> |
| <pre><pre class="playground"><code class="language-rust"> |
| <span class="boring">#![allow(unused)] |
| </span><span class="boring">fn main() { |
| </span>pub fn add(a: i32, b: i32) -> i32 { |
| a + b |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| #[test] |
| fn test_add() { |
| assert_eq!(add(2, 2), 4); |
| } |
| |
| #[test] |
| fn test_add_hundred() { |
| assert_eq!(add(100, 2), 102); |
| assert_eq!(add(2, 100), 102); |
| } |
| |
| #[test] |
| #[ignore] |
| fn ignored_test() { |
| assert_eq!(add(0, 0), 0); |
| } |
| } |
| <span class="boring">} |
| </span></code></pre></pre> |
| <pre><code class="language-shell">$ cargo test |
| running 3 tests |
| test tests::ignored_test ... ignored |
| test tests::test_add ... ok |
| test tests::test_add_hundred ... ok |
| |
| test result: ok. 2 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out |
| |
| Doc-tests tmp-ignore |
| |
| running 0 tests |
| |
| test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| |
| $ cargo test -- --ignored |
| running 1 test |
| test tests::ignored_test ... ok |
| |
| test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| |
| Doc-tests tmp-ignore |
| |
| running 0 tests |
| |
| test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out |
| </code></pre> |
| |
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