1.1.1. Extent¶

1.1.1:1 This document specifies:

• 1.1.1:2 The form of a program written in Rust;

• 1.1.1:3 The effect of translating and executing such a program;

• 1.1.1:4 The manner in which crates and modules may be combined to form Rust programs;

• 1.1.1:5 The language-defined libraries that a conforming tool is required to supply;

• 1.1.1:6 The violations that a conforming tool is required to detect, and the effect of attempting to translate or execute a program containing such violations;

• 1.1.1:7 The violations that a conforming tool is not required to detect.

1.1.1:8 This document does not specify:

• 1.1.1:9 The means by which a Rust program is transformed into object code executable by a processor;

• 1.1.1:10 The means by which translation or execution of Rust programs is invoked and the executing units are controlled;

• 1.1.1:11 The size or speed of the object code, or the relative execution speed of different language constructs;

• 1.1.1:12 The form or contents of any listings produced by a tool; in particular, the form or contents of error or warning messages;

• 1.1.1:13 The effect of undefined behavior;

• 1.1.1:14 The size of a program or program unit that will exceed the capacity of a conforming tool.

1.1.2. Structure¶

1.1.2:1 This document contains 22 chapters, 4 appendices, and an index.

1.1.2:2 The specification of the Rust language is separated into:

• 1.1.2:3 Chapters 1 through 22,

• 1.1.2:4 Appendices A through D

1.1.2:5 The specification is normative, except for the material in each of the items listed below, which is informative:

• 1.1.2:6 Text under an “Examples” heading.

• 1.1.2:7 Each subchapter whose title starts with the word “Example” or “Examples”.

1.1.2:8 All appendices are informative.

1.1.2:9 Each chapter is divided into subchapters that have a common structure. Each chapter and subchapter is then organized to include the following segments as is relevant to the topic:

Syntax

1.1.2:10 The syntax representation of a construct.

Legality Rules

1.1.2:11 Compile-time rules and facts for each construct. A construct is legal if it obeys all of the Legality Rules.

1.1.2:12 Legality Rules are verified after macro expansion takes place.

Dynamic Semantics

1.1.2:13 Run-time effects of each construct.

Undefined Behavior

1.1.2:14 Situations that result in unbounded errors.

Implementation Requirements

1.1.2:15 Additional requirements for conforming tools.

Examples

1.1.2:16 Examples illustrating the possible forms of a construct. This material is informative.

1.1.3. Conformity¶

Implementation Requirements

1.1.3:1 A conforming tool shall:

• 1.1.3:2 Translate and correctly execute legal programs written in Rust, provided that they are not so large as to exceed the capacity of the tool,

• 1.1.3:3 Identify all programs or program units that are so large as to exceed the capacity of the tool (or raise an appropriate exception at run time),

• 1.1.3:4 Identify all programs or program units that contain errors whose detection is required by this document,

• 1.1.3:5 Supply all language-defined library units required by this document,

• 1.1.3:6 Contain no variations except those explicitly permitted by this document, or those that are impossible or impractical to avoid given the tool’s execution environment,

• 1.1.3:7 Specify all such variations in the manner prescribed by this document.

1.1.3:8 The external effect of the execution of a Rust program is defined in terms of its interactions with its external environment. The following are defined as external interactions:

• 1.1.3:9 Any call on an foreign function, including any argument operands passed to it;

• 1.1.3:10 Any result returned or panic propagated from a program entry point or an exported function to an external caller;

• 1.1.3:11 The imported and exported values at the time of any other interaction with the external environment.

1.1.3:12 A tool that conforms to this document shall produce for the execution of a given Rust program a set of interactions with the external environment whose order and timing are consistent with the definitions and requirements of this document for the semantics of the given program.

1.1.3:13 A tool that conforms to this document shall support each capability required by the language as specified.

1.1.3:14 A tool that conforms to this document may provide additional attributes as long as their names are not the same as the names of built-in attributes.

1.1.4. Method of Description and Syntax Notation¶

1.1.4:1 The form of a Rust program is described by means of a context-free syntax together with context-dependent requirements expressed by narrative rules.

1.1.4:2 The meaning of a Rust program is described by means of narrative rules defining both the effects of each construct and the composition rules for constructs.

1.1.4:3 The context-free syntax of Rust is described using a simple variant of the Backus-Naur form. In particular:

• 1.1.4:4 A monospaced font is used to denote Rust syntax.

• 1.1.4:5 Words in PascalCase font are used to denote a syntactic category, for example:

FloatExponent

• 1.1.4:6 Words in bold font are used to indicate literal words and keywords, for example:

crate
proc_macro_derive
Self
tt

• 1.1.4:7 Characters in bold font are used to indicate literal characters and literal punctuation, for example:

1
F
{
&&
>>=

• 1.1.4:8 A character preceded by \ (bold reverse solidus) is used to denote an escaped character, for example:

\t
\\

• 1.1.4:9 A prefix followed by ? (question mark) is used to denote an optional prefix, for example:

IntegerSuffix?

• 1.1.4:10 A prefix followed by * (asterisk) is used to denote zero or more repetitions of the prefix, for example:

OuterAttributeOrDoc*

• 1.1.4:11 A prefix followed by + (plus sign) is used to denote one or more repetitions of the prefix, for example:

MacroMatch+

• 1.1.4:12 A prefix followed by L-H is used to denote the number of repetitions of the prefix within the range from L to H, inclusive. For example:

HexadecimalDigit1-6

• 1.1.4:13 [ ] (square brackets) indicate any character within, for example:

[8 a \r :]

• 1.1.4:14 ~[ ] (square brackets preceded by tilde) indicate any character except the characters within, for example:

~[8 a \r :]

• 1.1.4:15 [ - ] indicates any character within the specified range, inclusive. For example:

[a-f]

• 1.1.4:16 A | (vertical line) separates alternative items, for example:

self | Identifier | _

• 1.1.4:17 ( ) (parentheses) are used to group items, for example:

(, ConfigurationPredicate)