Rollup merge of #24548 - graydon:reference-tidying, r=steveklabnik

This just deletes some egregious lies and obsolete terminology -- all of which I originally wrote -- from the reference. I expect the reference itself will be deleted soon enough, but I found myself gritting teeth over these bits too much to let them into a 1.0 release.

Author: Manishearth

src/doc/complement-lang-faq.md

@@ -124,7 +124,7 @@ Yes. Calling C code from Rust is simple and exactly as efficient as calling C co
 
 Yes. The Rust code has to be exposed via an `extern` declaration, which makes it C-ABI compatible. Such a function can be passed to C code as a function pointer or, if given the `#[no_mangle]` attribute to disable symbol mangling, can be called directly from C code.
 
-## Why aren't function signatures inferred? Why only local slots?
+## Why aren't function signatures inferred? Why only local variables?
 
 * Mechanically, it simplifies the inference algorithm; inference only requires looking at one function at a time.
 * The same simplification goes double for human readers. A reader does not need an IDE running an inference algorithm across an entire crate to be able to guess at a function's argument types; it's always explicit and nearby.

src/doc/grammar.md

@@ -5,8 +5,7 @@
 This document is the primary reference for the Rust programming language grammar. It
 provides only one kind of material:
 
-  - Chapters that formally define the language grammar and, for each
-    construct.
+  - Chapters that formally define the language grammar.
 
 This document does not serve as an introduction to the language. Background
 familiarity with the language is assumed. A separate [guide] is available to
@@ -427,7 +426,7 @@ meta_seq : meta_item [ ',' meta_seq ] ? ;
 **FIXME:** grammar?
 
 A _declaration statement_ is one that introduces one or more *names* into the
-enclosing statement block. The declared names may denote new slots or new
+enclosing statement block. The declared names may denote new variables or new
 items.
 
 #### Item declarations
@@ -441,7 +440,7 @@ function, enumeration, structure, type, static, trait, implementation or module
 scope to a narrow region containing all of its uses; it is otherwise identical
 in meaning to declaring the item outside the statement block.
 
-#### Slot declarations
+#### Variable declarations
 
 ```antlr
 let_decl : "let" pat [':' type ] ? [ init ] ? ';' ;
@@ -763,7 +762,7 @@ bound := path | lifetime
 
 ### Memory ownership
 
-### Memory slots
+### Variables
 
 ### Boxes
 

src/doc/reference.md

@@ -564,7 +564,7 @@ type_path_tail : '<' type_expr [ ',' type_expr ] + '>'
 
 A _path_ is a sequence of one or more path components _logically_ separated by
 a namespace qualifier (`::`). If a path consists of only one component, it may
-refer to either an [item](#items) or a [slot](#memory-slots) in a local control
+refer to either an [item](#items) or a [variable](#variables) in a local control
 scope. If a path has multiple components, it refers to an item.
 
 Every item has a _canonical path_ within its crate, but the path naming an item
@@ -735,13 +735,11 @@ Rust syntax is restricted in two ways:
 
 # Crates and source files
 
-Rust is a *compiled* language. Its semantics obey a *phase distinction*
-between compile-time and run-time. Those semantic rules that have a *static
-interpretation* govern the success or failure of compilation. We refer to
-these rules as "static semantics". Semantic rules called "dynamic semantics"
-govern the behavior of programs at run-time. A program that fails to compile
-due to violation of a compile-time rule has no defined dynamic semantics; the
-compiler should halt with an error report, and produce no executable artifact.
+Rust is a *compiled* language. Its semantics obey a *phase distinction* between
+compile-time and run-time. Those semantic rules that have a *static
+interpretation* govern the success or failure of compilation. Those semantics
+that have a *dynamic interpretation* govern the behavior of the program at
+run-time.
 
 The compilation model centers on artifacts called _crates_. Each compilation
 processes a single crate in source form, and if successful, produces a single
@@ -1064,9 +1062,9 @@ fn main() {}
 A _function item_ defines a sequence of [statements](#statements) and an
 optional final [expression](#expressions), along with a name and a set of
 parameters. Functions are declared with the keyword `fn`. Functions declare a
-set of *input* [*slots*](#memory-slots) as parameters, through which the caller
-passes arguments into the function, and an *output* [*slot*](#memory-slots)
-through which the function passes results back to the caller.
+set of *input* [*variables*](#variables) as parameters, through which the caller
+passes arguments into the function, and the *output* [*type*](#types)
+of the value the function will return to its caller on completion.
 
 A function may also be copied into a first-class *value*, in which case the
 value has the corresponding [*function type*](#function-types), and can be used
@@ -1229,7 +1227,7 @@ be undesired.
 #### Diverging functions
 
 A special kind of function can be declared with a `!` character where the
-output slot type would normally be. For example:
+output type would normally be. For example:
 
 ```
 fn my_err(s: &str) -> ! {
@@ -1302,18 +1300,11 @@ contiguous stack segments like C.
 
 A _type alias_ defines a new name for an existing [type](#types). Type
 aliases are declared with the keyword `type`. Every value has a single,
-specific type; the type-specified aspects of a value include:
+specific type, but may implement several different traits, or be compatible with
+several different type constraints.
 
-* Whether the value is composed of sub-values or is indivisible.
-* Whether the value represents textual or numerical information.
-* Whether the value represents integral or floating-point information.
-* The sequence of memory operations required to access the value.
-* The [kind](#type-kinds) of the type.
-
-For example, the type `(u8, u8)` defines the set of immutable values that are
-composite pairs, each containing two unsigned 8-bit integers accessed by
-pattern-matching and laid out in memory with the `x` component preceding the
-`y` component:
+For example, the following defines the type `Point` as a synonym for the type
+`(u8, u8)`, the type of pairs of unsigned 8 bit integers.:
 
 ```
 type Point = (u8, u8);
@@ -2551,7 +2542,7 @@ statements](#expression-statements).
 ### Declaration statements
 
 A _declaration statement_ is one that introduces one or more *names* into the
-enclosing statement block. The declared names may denote new slots or new
+enclosing statement block. The declared names may denote new variables or new
 items.
 
 #### Item declarations
@@ -2566,18 +2557,18 @@ in meaning to declaring the item outside the statement block.
 > **Note**: there is no implicit capture of the function's dynamic environment when
 > declaring a function-local item.
 
-#### Slot declarations
+#### Variable declarations
 
 ```{.ebnf .gram}
 let_decl : "let" pat [':' type ] ? [ init ] ? ';' ;
 init : [ '=' ] expr ;
 ```
 
-A _slot declaration_ introduces a new set of slots, given by a pattern. The
+A _variable declaration_ introduces a new set of variable, given by a pattern. The
 pattern may be followed by a type annotation, and/or an initializer expression.
 When no type annotation is given, the compiler will infer the type, or signal
 an error if insufficient type information is available for definite inference.
-Any slots introduced by a slot declaration are visible from the point of
+Any variables introduced by a variable declaration are visible from the point of
 declaration until the end of the enclosing block scope.
 
 ### Expression statements
@@ -2632,7 +2623,7 @@ of any reference that points to it.
 
 #### Moved and copied types
 
-When a [local variable](#memory-slots) is used as an
+When a [local variable](#variables) is used as an
 [rvalue](#lvalues,-rvalues-and-temporaries) the variable will either be moved
 or copied, depending on its type. All values whose type implements `Copy` are
 copied, all others are moved.
@@ -3042,10 +3033,9 @@ paren_expr_list : '(' expr_list ')' ;
 call_expr : expr paren_expr_list ;
 ```
 
-A _call expression_ invokes a function, providing zero or more input slots and
-an optional reference slot to serve as the function's output, bound to the
-`lval` on the right hand side of the call. If the function eventually returns,
-then the expression completes.
+A _call expression_ invokes a function, providing zero or more input variables
+and an optional location to move the function's output into. If the function
+eventually returns, then the expression completes.
 
 Some examples of call expressions:
 
@@ -3456,9 +3446,9 @@ return_expr : "return" expr ? ;
 ```
 
 Return expressions are denoted with the keyword `return`. Evaluating a `return`
-expression moves its argument into the output slot of the current function,
-destroys the current function activation frame, and transfers control to the
-caller frame.
+expression moves its argument into the designated output location for the
+current function call, destroys the current function activation frame, and
+transfers control to the caller frame.
 
 An example of a `return` expression:
 
@@ -3475,7 +3465,7 @@ fn max(a: i32, b: i32) -> i32 {
 
 ## Types
 
-Every slot, item and value in a Rust program has a type. The _type_ of a
+Every variable, item and value in a Rust program has a type. The _type_ of a
 *value* defines the interpretation of the memory holding it.
 
 Built-in types and type-constructors are tightly integrated into the language,
@@ -3493,7 +3483,7 @@ The primitive types are the following:
 * The machine-dependent integer and floating-point types.
 
 [^unittype]: The "unit" value `()` is *not* a sentinel "null pointer" value for
-    reference slots; the "unit" type is the implicit return type from functions
+    reference variables; the "unit" type is the implicit return type from functions
     otherwise lacking a return type, and can be used in other contexts (such as
     message-sending or type-parametric code) as a zero-size type.]
 
@@ -3831,29 +3821,33 @@ impl Printable for String {
 `self` refers to the value of type `String` that is the receiver for a call to
 the method `make_string`.
 
-# The `Copy` trait
+# Special traits
+
+Several traits define special evaluation behavior.
 
-Rust has a special trait, `Copy`, which when implemented changes the semantics
-of a value. Values whose type implements `Copy` are copied rather than moved
-upon assignment.
+## The `Copy` trait
 
-# The `Sized` trait
+The `Copy` trait changes the semantics of a type implementing it. Values whose
+type implements `Copy` are copied rather than moved upon assignment.
 
-`Sized` is a special trait which indicates that the size of this type is known
-at compile-time.
+## The `Sized` trait
 
-# The `Drop` trait
+The `Sized` trait indicates that the size of this type is known at compile-time.
+
+## The `Drop` trait
 
 The `Drop` trait provides a destructor, to be run whenever a value of this type
 is to be destroyed.
 
 # Memory model
 
 A Rust program's memory consists of a static set of *items* and a *heap*.
-Immutable portions of the heap may be shared between threads, mutable portions
-may not.
+Immutable portions of the heap may be safely shared between threads, mutable
+portions may not be safely shared, but several mechanisms for effectively-safe
+sharing of mutable values, built on unsafe code but enforcing a safe locking
+discipline, exist in the standard library.
 
-Allocations in the stack consist of *slots*, and allocations in the heap
+Allocations in the stack consist of *variables*, and allocations in the heap
 consist of *boxes*.
 
 ### Memory allocation and lifetime
@@ -3872,10 +3866,11 @@ in the heap, heap allocations may outlive the frame they are allocated within.
 When a stack frame is exited, its local allocations are all released, and its
 references to boxes are dropped.
 
-### Memory slots
+### Variables
 
-A _slot_ is a component of a stack frame, either a function parameter, a
-[temporary](#lvalues,-rvalues-and-temporaries), or a local variable.
+A _variable_ is a component of a stack frame, either a named function parameter,
+an anonymous [temporary](#lvalues,-rvalues-and-temporaries), or a named local
+variable.
 
 A _local variable_ (or *stack-local* allocation) holds a value directly,
 allocated within the stack's memory. The value is a part of the stack frame.
@@ -3888,7 +3883,7 @@ Box<i32>, y: Box<i32>)` declare one mutable variable `x` and one immutable
 variable `y`).
 
 Methods that take either `self` or `Box<Self>` can optionally place them in a
-mutable slot by prefixing them with `mut` (similar to regular arguments):
+mutable variable by prefixing them with `mut` (similar to regular arguments):
 
 ```
 trait Changer {
@@ -3903,44 +3898,7 @@ state. Subsequent statements within a function may or may not initialize the
 local variables. Local variables can be used only after they have been
 initialized; this is enforced by the compiler.
 
-# Runtime services, linkage and debugging
-
-The Rust _runtime_ is a relatively compact collection of Rust code that
-provides fundamental services and datatypes to all Rust threads at run-time. It
-is smaller and simpler than many modern language runtimes. It is tightly
-integrated into the language's execution model of memory, threads, communication
-and logging.
-
-### Memory allocation
-
-The runtime memory-management system is based on a _service-provider
-interface_, through which the runtime requests blocks of memory from its
-environment and releases them back to its environment when they are no longer
-needed. The default implementation of the service-provider interface consists
-of the C runtime functions `malloc` and `free`.
-
-The runtime memory-management system, in turn, supplies Rust threads with
-facilities for allocating releasing stacks, as well as allocating and freeing
-heap data.
-
-### Built in types
-
-The runtime provides C and Rust code to assist with various built-in types,
-such as arrays, strings, and the low level communication system (ports,
-channels, threads).
-
-Support for other built-in types such as simple types, tuples and enums is
-open-coded by the Rust compiler.
-
-### Thread scheduling and communication
-
-The runtime provides code to manage inter-thread communication. This includes
-the system of thread-lifecycle state transitions depending on the contents of
-queues, as well as code to copy values between queues and their recipients and
-to serialize values for transmission over operating-system inter-process
-communication facilities.
-
-### Linkage
+# Linkage
 
 The Rust compiler supports various methods to link crates together both
 statically and dynamically. This section will explore the various methods to