auto merge of #9013 : alexcrichton/rust/generated-unsafe-blocks, r=sanxiyn

This way syntax extensions can generate unsafe blocks without worrying about them generating unnecessary unsafe warnings. Perhaps a special keyword could be added to be used in macros, but I don't think that's the best solution.

Currently if you use `format!` and friends in an `unsafe` block you're guaranteed to get some unused-unsafe warnings which is unfortunate. We normally do want these warnings, but I'm ok ignoring them in the case of compiler-generated unsafe blocks. I tried to do this in the least intrusive way possible, but others may have better ideas about how to do this.

4 files changed, 10 insertions, 4 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 8d557125d37..ef2e557b6ea 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -479,7 +479,13 @@ pub struct Field {
 #[deriving(Clone, Eq, Encodable, Decodable, IterBytes)]
 pub enum BlockCheckMode {
     DefaultBlock,
-    UnsafeBlock,
+    UnsafeBlock(UnsafeSource),
+}
+
+#[deriving(Clone, Eq, Encodable, Decodable, IterBytes)]
+pub enum UnsafeSource {
+    CompilerGenerated,
+    UserProvided,
 }
 
 #[deriving(Clone, Eq, Encodable, Decodable,IterBytes)]
diff --git a/src/libsyntax/ext/ifmt.rs b/src/libsyntax/ext/ifmt.rs
index b7722ffc297..486069db4f0 100644
--- a/src/libsyntax/ext/ifmt.rs
+++ b/src/libsyntax/ext/ifmt.rs
@@ -632,7 +632,7 @@ impl Context {
            stmts: ~[],
            expr: Some(result),
            id: ast::DUMMY_NODE_ID,
-           rules: ast::UnsafeBlock,
+           rules: ast::UnsafeBlock(ast::CompilerGenerated),
            span: self.fmtsp,
         });
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 4adc34d75a7..b5772a9eede 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1792,7 +1792,7 @@ impl Parser {
         } else if self.eat_keyword(keywords::Match) {
             return self.parse_match_expr();
         } else if self.eat_keyword(keywords::Unsafe) {
-            return self.parse_block_expr(lo, UnsafeBlock);
+            return self.parse_block_expr(lo, UnsafeBlock(ast::UserProvided));
         } else if *self.token == token::LBRACKET {
             self.bump();
             let mutbl = self.parse_mutability();
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 55f052d769d..9b9b157c9d8 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -951,7 +951,7 @@ pub fn print_possibly_embedded_block_(s: @ps,
                                       attrs: &[ast::Attribute],
                                       close_box: bool) {
     match blk.rules {
-      ast::UnsafeBlock => word_space(s, "unsafe"),
+      ast::UnsafeBlock(*) => word_space(s, "unsafe"),
       ast::DefaultBlock => ()
     }
     maybe_print_comment(s, blk.span.lo);