Auto merge of #49124 - abonander:attr-macro-stmt-expr, r=abonander

Expand Attributes on Statements and Expressions

This enables attribute-macro expansion on statements and expressions while retaining the `stmt_expr_attributes` feature requirement for attributes on expressions.

closes #41475
cc #38356  @petrochenkov @jseyfried
r? @nrc

src/test/compile-fail-fulldeps/auxiliary/macro_crate_test.rs

@@ -93,6 +93,8 @@ fn expand_into_foo_multi(cx: &mut ExtCtxt,
                 }
             })
         }
+        // these are covered in proc_macro/attr-stmt-expr.rs
+        Annotatable::Stmt(_) | Annotatable::Expr(_) => panic!("expected item")
     }
 }
 
@@ -145,6 +147,8 @@ fn expand_duplicate(cx: &mut ExtCtxt,
             new_it.ident = copy_name;
             push(Annotatable::TraitItem(P(new_it)));
         }
+        // covered in proc_macro/attr-stmt-expr.rs
+        Annotatable::Stmt(_) | Annotatable::Expr(_) => panic!("expected item")
     }
 }
 

src/test/compile-fail-fulldeps/proc-macro/attr-invalid-exprs.rs

@@ -0,0 +1,38 @@
+// Copyright 2018 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.
+
+// aux-build:attr-stmt-expr.rs
+// ignore-stage1
+
+//! Attributes producing expressions in invalid locations
+
+#![feature(proc_macro, stmt_expr_attributes)]
+
+extern crate attr_stmt_expr;
+use attr_stmt_expr::{duplicate, no_output};
+
+fn main() {
+    let _ = #[no_output] "Hello, world!";
+    //~^ ERROR expected expression, found `<eof>`
+
+    let _ = #[duplicate] "Hello, world!";
+    //~^ ERROR macro expansion ignores token `,` and any following
+
+    let _ = {
+        #[no_output]
+        "Hello, world!"
+    };
+
+    let _ = {
+        #[duplicate]
+        //~^ ERROR macro expansion ignores token `,` and any following
+        "Hello, world!"
+    };
+}

src/test/compile-fail-fulldeps/proc-macro/attr-stmt-expr.rs

@@ -0,0 +1,38 @@
+// Copyright 2018 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.
+
+// aux-build:attr-stmt-expr.rs
+// ignore-stage1
+
+#![feature(proc_macro)]
+
+extern crate attr_stmt_expr;
+use attr_stmt_expr::{expect_let, expect_print_stmt, expect_expr, expect_print_expr};
+
+fn print_str(string: &'static str) {
+    // macros are handled a bit differently
+    #[expect_print_expr]
+    //~^ ERROR attributes on expressions are experimental
+    //~| HELP add #![feature(stmt_expr_attributes)] to the crate attributes to enable
+    println!("{}", string)
+}
+
+fn main() {
+    #[expect_let]
+    let string = "Hello, world!";
+
+    #[expect_print_stmt]
+    println!("{}", string);
+
+    #[expect_expr]
+    //~^ ERROR attributes on expressions are experimental
+    //~| HELP add #![feature(stmt_expr_attributes)] to the crate attributes to enable
+    print_str("string")
+}

src/test/compile-fail-fulldeps/proc-macro/auxiliary/attr-stmt-expr.rs

@@ -0,0 +1,59 @@
+// Copyright 2018 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.
+
+// no-prefer-dynamic
+
+#![feature(proc_macro)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_attribute]
+pub fn expect_let(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "let string = \"Hello, world!\";");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn expect_print_stmt(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "println!(\"{}\" , string);");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn expect_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "print_str(\"string\")");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn expect_print_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "println!(\"{}\" , string)");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn duplicate(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    format!("{}, {}", item, item).parse().unwrap()
+}
+
+#[proc_macro_attribute]
+pub fn no_output(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert!(!item.to_string().is_empty());
+    "".parse().unwrap()
+}

src/test/run-pass-fulldeps/auxiliary/macro_crate_test.rs

@@ -96,6 +96,8 @@ fn expand_into_foo_multi(cx: &mut ExtCtxt,
                 }
             })
         ],
+        // these are covered in proc_macro/attr-stmt-expr.rs
+        Annotatable::Stmt(_) | Annotatable::Expr(_) => panic!("expected item"),
     }
 }
 
@@ -140,6 +142,8 @@ fn expand_duplicate(cx: &mut ExtCtxt,
             new_it.ident = copy_name;
             push(Annotatable::TraitItem(P(new_it)));
         }
+        // these are covered in proc_macro/attr-stmt-expr.rs
+        Annotatable::Stmt(_) | Annotatable::Expr(_) => panic!("expected item")
     }
 }
 

src/test/run-pass-fulldeps/proc-macro/attr-stmt-expr.rs

@@ -0,0 +1,34 @@
+// Copyright 2018 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.
+
+// aux-build:attr-stmt-expr.rs
+// ignore-stage1
+
+#![feature(proc_macro, stmt_expr_attributes)]
+
+extern crate attr_stmt_expr;
+use attr_stmt_expr::{expect_let, expect_print_stmt, expect_expr, expect_print_expr};
+
+fn print_str(string: &'static str) {
+    // macros are handled a bit differently
+    #[expect_print_expr]
+    println!("{}", string)
+}
+
+fn main() {
+    #[expect_let]
+    let string = "Hello, world!";
+
+    #[expect_print_stmt]
+    println!("{}", string);
+
+    #[expect_expr]
+    print_str("string")
+}

src/test/run-pass-fulldeps/proc-macro/auxiliary/attr-stmt-expr.rs

@@ -0,0 +1,46 @@
+// Copyright 2018 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.
+
+// no-prefer-dynamic
+
+#![feature(proc_macro)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro_attribute]
+pub fn expect_let(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "let string = \"Hello, world!\";");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn expect_print_stmt(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "println!(\"{}\" , string);");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn expect_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "print_str(\"string\")");
+    item
+}
+
+#[proc_macro_attribute]
+pub fn expect_print_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
+    assert!(attr.to_string().is_empty());
+    assert_eq!(item.to_string(), "println!(\"{}\" , string)");
+    item
+}

src/test/ui/feature-gate-stmt_expr_attributes.rs

@@ -9,6 +9,6 @@
 // except according to those terms.
 
 const X: i32 = #[allow(dead_code)] 8;
-//~^ ERROR attributes on non-item statements and expressions are experimental. (see issue #15701)
+//~^ ERROR attributes on expressions are experimental. (see issue #15701)
 
 fn main() {}

src/test/ui/feature-gate-stmt_expr_attributes.stderr

@@ -1,4 +1,4 @@
-error[E0658]: attributes on non-item statements and expressions are experimental. (see issue #15701)
+error[E0658]: attributes on expressions are experimental. (see issue #15701)
   --> $DIR/feature-gate-stmt_expr_attributes.rs:11:16
    |
 LL | const X: i32 = #[allow(dead_code)] 8;