Add toggle for `parse_meta_item` unsafe parsing

This makes it possible for the `unsafe(...)` syntax to only be
valid at the top level, and the `NestedMetaItem`s will automatically
reject `unsafe(...)`.

9 files changed, 157 insertions, 25 deletions

diff --git a/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs b/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs
index 7f0d6a0cf8b..b8edb4aab90 100644
--- a/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/derive-unsafe-attributes.rs
@@ -1,6 +1,12 @@
 #![feature(unsafe_attributes)]
 
-#[derive(unsafe(Debug))] //~ ERROR: traits in `#[derive(...)]` don't accept `unsafe(...)`
+#[derive(unsafe(Debug))]
+//~^ ERROR: expected identifier, found keyword `unsafe`
+//~| ERROR: traits in `#[derive(...)]` don't accept arguments
+//~| ERROR: expected identifier, found keyword `unsafe`
+//~| ERROR: expected identifier, found keyword `unsafe`
+//~| ERROR: cannot find derive macro `r#unsafe` in this scope
+//~| ERROR: cannot find derive macro `r#unsafe` in this scope
 struct Foo;
 
 #[unsafe(derive(Debug))] //~ ERROR: is not an unsafe attribute
diff --git a/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr
index 22010c61b5f..c40a5512fd5 100644
--- a/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/derive-unsafe-attributes.stderr
@@ -1,16 +1,65 @@
-error: traits in `#[derive(...)]` don't accept `unsafe(...)`
+error: expected identifier, found keyword `unsafe`
   --> $DIR/derive-unsafe-attributes.rs:3:10
    |
 LL | #[derive(unsafe(Debug))]
-   |          ^^^^^^
+   |          ^^^^^^ expected identifier, found keyword
+   |
+help: escape `unsafe` to use it as an identifier
+   |
+LL | #[derive(r#unsafe(Debug))]
+   |          ++
+
+error: traits in `#[derive(...)]` don't accept arguments
+  --> $DIR/derive-unsafe-attributes.rs:3:16
+   |
+LL | #[derive(unsafe(Debug))]
+   |                ^^^^^^^ help: remove the arguments
 
 error: `derive` is not an unsafe attribute
-  --> $DIR/derive-unsafe-attributes.rs:6:3
+  --> $DIR/derive-unsafe-attributes.rs:12:3
    |
 LL | #[unsafe(derive(Debug))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
-error: aborting due to 2 previous errors
+error: expected identifier, found keyword `unsafe`
+  --> $DIR/derive-unsafe-attributes.rs:3:10
+   |
+LL | #[derive(unsafe(Debug))]
+   |          ^^^^^^ expected identifier, found keyword
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: escape `unsafe` to use it as an identifier
+   |
+LL | #[derive(r#unsafe(Debug))]
+   |          ++
+
+error: expected identifier, found keyword `unsafe`
+  --> $DIR/derive-unsafe-attributes.rs:3:10
+   |
+LL | #[derive(unsafe(Debug))]
+   |          ^^^^^^ expected identifier, found keyword
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: escape `unsafe` to use it as an identifier
+   |
+LL | #[derive(r#unsafe(Debug))]
+   |          ++
+
+error: cannot find derive macro `r#unsafe` in this scope
+  --> $DIR/derive-unsafe-attributes.rs:3:10
+   |
+LL | #[derive(unsafe(Debug))]
+   |          ^^^^^^
+
+error: cannot find derive macro `r#unsafe` in this scope
+  --> $DIR/derive-unsafe-attributes.rs:3:10
+   |
+LL | #[derive(unsafe(Debug))]
+   |          ^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 7 previous errors
 
diff --git a/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr
index ea82bac6df0..950b2636993 100644
--- a/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/double-unsafe-attributes.stderr
@@ -13,7 +13,7 @@ error: `r#unsafe` is not an unsafe attribute
   --> $DIR/double-unsafe-attributes.rs:3:3
    |
 LL | #[unsafe(unsafe(no_mangle))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
diff --git a/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr
index a2e56087d16..f39074b613d 100644
--- a/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr
@@ -2,7 +2,7 @@ error: `cfg` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:5:3
    |
 LL | #[unsafe(cfg(any()))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -10,7 +10,7 @@ error: `cfg_attr` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:8:3
    |
 LL | #[unsafe(cfg_attr(any(), allow(dead_code)))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -18,7 +18,7 @@ error: `test` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:11:3
    |
 LL | #[unsafe(test)]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -26,7 +26,7 @@ error: `ignore` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:14:3
    |
 LL | #[unsafe(ignore = "test")]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -34,7 +34,7 @@ error: `should_panic` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:17:3
    |
 LL | #[unsafe(should_panic(expected = "test"))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -42,7 +42,7 @@ error: `macro_use` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:20:3
    |
 LL | #[unsafe(macro_use)]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -50,7 +50,7 @@ error: `macro_export` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:22:7
    |
 LL |     #[unsafe(macro_export)]
-   |       ^^^^^^
+   |       ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -58,7 +58,7 @@ error: `used` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:28:3
    |
 LL | #[unsafe(used)]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
diff --git a/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs b/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
index caf6c6dc8ff..f29a5b3252b 100644
--- a/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
@@ -13,6 +13,7 @@ pub fn b() {}
 
 #[proc_macro_derive(unsafe(Foo))]
 //~^ ERROR attribute is only usable with crates of the `proc-macro` crate type
+//~| ERROR: expected identifier, found keyword `unsafe`
 pub fn c() {}
 
 #[unsafe(proc_macro_attribute)]
@@ -24,4 +25,13 @@ pub fn d() {}
 //~^ ERROR: is not an unsafe attribute
 pub fn e() {}
 
+#[unsafe(allow(unsafe(dead_code)))]
+//~^ ERROR: is not an unsafe attribute
+//~| ERROR: malformed lint attribute input
+//~| ERROR: malformed lint attribute input
+//~| ERROR: expected identifier, found keyword `unsafe`
+//~| ERROR: malformed lint attribute input
+//~| ERROR: malformed lint attribute input
+pub fn f() {}
+
 fn main() {}
diff --git a/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
index 346d2c2e9ae..79d34d458bd 100644
--- a/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
+++ b/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
@@ -1,8 +1,22 @@
+error[E0452]: malformed lint attribute input
+  --> $DIR/proc-unsafe-attributes.rs:28:16
+   |
+LL | #[unsafe(allow(unsafe(dead_code)))]
+   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+
+error[E0452]: malformed lint attribute input
+  --> $DIR/proc-unsafe-attributes.rs:28:16
+   |
+LL | #[unsafe(allow(unsafe(dead_code)))]
+   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: `proc_macro` is not an unsafe attribute
   --> $DIR/proc-unsafe-attributes.rs:3:3
    |
 LL | #[unsafe(proc_macro)]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
@@ -10,26 +24,56 @@ error: `proc_macro_derive` is not an unsafe attribute
   --> $DIR/proc-unsafe-attributes.rs:9:3
    |
 LL | #[unsafe(proc_macro_derive(Foo))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
+error: expected identifier, found keyword `unsafe`
+  --> $DIR/proc-unsafe-attributes.rs:14:21
+   |
+LL | #[proc_macro_derive(unsafe(Foo))]
+   |                     ^^^^^^ expected identifier, found keyword
+   |
+help: escape `unsafe` to use it as an identifier
+   |
+LL | #[proc_macro_derive(r#unsafe(Foo))]
+   |                     ++
+
 error: `proc_macro_attribute` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:18:3
+  --> $DIR/proc-unsafe-attributes.rs:19:3
    |
 LL | #[unsafe(proc_macro_attribute)]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
 error: `allow` is not an unsafe attribute
-  --> $DIR/proc-unsafe-attributes.rs:23:3
+  --> $DIR/proc-unsafe-attributes.rs:24:3
    |
 LL | #[unsafe(allow(dead_code))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
+error: `allow` is not an unsafe attribute
+  --> $DIR/proc-unsafe-attributes.rs:28:3
+   |
+LL | #[unsafe(allow(unsafe(dead_code)))]
+   |   ^^^^^^ this is not an unsafe attribute
+   |
+   = note: extraneous unsafe is not allowed in attributes
+
+error: expected identifier, found keyword `unsafe`
+  --> $DIR/proc-unsafe-attributes.rs:28:16
+   |
+LL | #[unsafe(allow(unsafe(dead_code)))]
+   |                ^^^^^^ expected identifier, found keyword
+   |
+help: escape `unsafe` to use it as an identifier
+   |
+LL | #[unsafe(allow(r#unsafe(dead_code)))]
+   |                ++
+
 error: the `#[proc_macro]` attribute is only usable with crates of the `proc-macro` crate type
   --> $DIR/proc-unsafe-attributes.rs:3:1
    |
@@ -49,10 +93,27 @@ LL | #[proc_macro_derive(unsafe(Foo))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: the `#[proc_macro_attribute]` attribute is only usable with crates of the `proc-macro` crate type
-  --> $DIR/proc-unsafe-attributes.rs:18:1
+  --> $DIR/proc-unsafe-attributes.rs:19:1
    |
 LL | #[unsafe(proc_macro_attribute)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error[E0452]: malformed lint attribute input
+  --> $DIR/proc-unsafe-attributes.rs:28:16
+   |
+LL | #[unsafe(allow(unsafe(dead_code)))]
+   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0452]: malformed lint attribute input
+  --> $DIR/proc-unsafe-attributes.rs:28:16
+   |
+LL | #[unsafe(allow(unsafe(dead_code)))]
+   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 15 previous errors
 
+For more information about this error, try `rustc --explain E0452`.
diff --git a/tests/ui/attributes/unsafe/unsafe-attributes.rs b/tests/ui/attributes/unsafe/unsafe-attributes.rs
index e7620a18048..33a412add50 100644
--- a/tests/ui/attributes/unsafe/unsafe-attributes.rs
+++ b/tests/ui/attributes/unsafe/unsafe-attributes.rs
@@ -4,4 +4,10 @@
 #[unsafe(no_mangle)]
 fn a() {}
 
+#[unsafe(export_name = "foo")]
+fn b() {}
+
+#[cfg_attr(any(), unsafe(no_mangle))]
+static VAR2: u32 = 1;
+
 fn main() {}
diff --git a/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr b/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr
index 0602af34e4f..584b0ea797d 100644
--- a/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr
+++ b/tests/ui/attributes/unsafe/unsafe-safe-attribute.stderr
@@ -2,7 +2,7 @@ error: `repr` is not an unsafe attribute
   --> $DIR/unsafe-safe-attribute.rs:3:3
    |
 LL | #[unsafe(repr(C))]
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes
 
diff --git a/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr b/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr
index 584dacf4d8c..26b5e4e37b9 100644
--- a/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr
+++ b/tests/ui/attributes/unsafe/unsafe-safe-attribute_diagnostic.stderr
@@ -2,7 +2,7 @@ error: `diagnostic::on_unimplemented` is not an unsafe attribute
   --> $DIR/unsafe-safe-attribute_diagnostic.rs:3:3
    |
 LL | #[unsafe(diagnostic::on_unimplemented(
-   |   ^^^^^^
+   |   ^^^^^^ this is not an unsafe attribute
    |
    = note: extraneous unsafe is not allowed in attributes