auto merge of #14145 : pnkfelix/rust/fsk-better-svh-via-visitor, r=alexcrichton

Teach SVH computation to ignore more implementation artifacts.

In particular, this version of strict version hash (SVH) works much
like the deriving(Hash)-based implementation did, except that it
deliberately:

  1. skips over content known not affect the generated crates, and,

  2. uses a content-based hash for names instead of using the value of
     the `Name` index itself, which can differ depending on the order
     in which strings are interned (which in turn is affected by
     e.g. the presence of `--cfg` options on the command line).

Fix #14132.

Author: bors

src/librustc/back/svh.rs

@@ -61,7 +61,17 @@ pub fn generics_of_fn(fk: &FnKind) -> Generics {
     }
 }
 
+/// Each method of the Visitor trait is a hook to be potentially
+/// overriden.  Each method's default implementation recursively visits
+/// the substructure of the input via the corresponding `walk` method;
+/// e.g. the `visit_mod` method by default calls `visit::walk_mod`.
+///
+/// If you want to ensure that your code handles every variant
+/// explicitly, you need to override each method.  (And you also need
+/// to monitor future changes to `Visitor` in case a new method with a
+/// new default implementation gets introduced.)
 pub trait Visitor<E: Clone> {
+
     fn visit_ident(&mut self, _sp: Span, _ident: Ident, _e: E) {
         /*! Visit the idents */
     }
@@ -179,9 +189,9 @@ pub fn walk_local<E: Clone, V: Visitor<E>>(visitor: &mut V, local: &Local, env:
     }
 }
 
-fn walk_explicit_self<E: Clone, V: Visitor<E>>(visitor: &mut V,
-                                               explicit_self: &ExplicitSelf,
-                                               env: E) {
+pub fn walk_explicit_self<E: Clone, V: Visitor<E>>(visitor: &mut V,
+                                                   explicit_self: &ExplicitSelf,
+                                                   env: E) {
     match explicit_self.node {
         SelfStatic | SelfValue | SelfUniq => {}
         SelfRegion(ref lifetime, _) => {

src/libsyntax/visit.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+pub fn foo<T:U>(_: int) -> int {
+    3
+}
+
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-base.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+pub fn foo<T:U>(_: int) -> int {
+    0
+}
+
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-change-lit.rs

@@ -0,0 +1,39 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+#[cfg(some_flag)]
+pub fn foo<T:U>(_: int) -> int {
+    3
+}
+
+#[cfg(not(some_flag))]
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-change-significant-cfg.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+pub fn foo<T:V>(_: int) -> int {
+    3
+}
+
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-change-trait-bound.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+pub fn foo<T:U>(_: i32) -> int {
+    3
+}
+
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-change-type-arg.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+pub fn foo<T:U>(_: int) -> i64 {
+    3
+}
+
+pub fn an_unused_name() -> i32 {
+    4
+}

src/test/auxiliary/svh-a-change-type-ret.rs

@@ -0,0 +1,37 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : i32 = 2;
+
+pub fn foo<T:U>(_: int) -> int {
+    3
+}
+
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-change-type-static.rs

@@ -0,0 +1,38 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+pub fn foo<T:U>(_: int) -> int {
+    // a comment does not affect the svh
+    3
+}
+
+pub fn an_unused_name() -> int {
+    4
+}

src/test/auxiliary/svh-a-comment.rs

@@ -0,0 +1,40 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `svh-a-*.rs` files are all deviations from the base file
+//! svh-a-base.rs with some difference (usually in `fn foo`) that
+//! should not affect the strict version hash (SVH) computation
+//! (#14132).
+
+#![feature(macro_rules)]
+
+#![crate_id = "a"]
+
+macro_rules! three {
+    () => { 3 }
+}
+
+pub trait U {}
+pub trait V {}
+impl U for () {}
+impl V for () {}
+
+static A_CONSTANT : int = 2;
+
+// Adding some documentation does not affect the svh.
+
+/// foo always returns three.
+pub fn foo<T:U>(_: int) -> int {
+    3
+}
+
+pub fn an_unused_name() -> int {
+    4
+}