Remove the MacroVisitor pass.

This pass was supposed to check use of gated features before
`#[cfg]`-stripping but this was not the case since it in fact happens
after. Checks that are actually important and must be done before macro
expansion are now made where the features are actually used. Close #32648.
Also ensure that attributes on macro-generated macro invocations are
checked as well. Close #32782 and #32655.

2 files changed, 51 insertions, 109 deletions

diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index bc8d5cd7703..16b465ba36e 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -35,6 +35,16 @@ use std_inject;
 use std::collections::HashSet;
 use std::env;
 
+// this function is called to detect use of feature-gated or invalid attributes
+// on macro invoations since they will not be detected after macro expansion
+fn check_attributes(attrs: &[ast::Attribute], fld: &MacroExpander) {
+    for attr in attrs.iter() {
+        feature_gate::check_attribute(&attr, &fld.cx.parse_sess.span_diagnostic,
+                                      &fld.cx.parse_sess.codemap(),
+                                      &fld.cx.ecfg.features.unwrap());
+    }
+}
+
 pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
     let expr_span = e.span;
     return e.and_then(|ast::Expr {id, node, span, attrs}| match node {
@@ -42,6 +52,9 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
         // expr_mac should really be expr_ext or something; it's the
         // entry-point for all syntax extensions.
         ast::ExprKind::Mac(mac) => {
+            if let Some(ref attrs) = attrs {
+                check_attributes(attrs, fld);
+            }
 
             // Assert that we drop any macro attributes on the floor here
             drop(attrs);
@@ -367,6 +380,8 @@ pub fn expand_item_mac(it: P<ast::Item>,
         _ => fld.cx.span_bug(it.span, "invalid item macro invocation")
     });
 
+    check_attributes(&attrs, fld);
+
     let fm = fresh_mark();
     let items = {
         let expanded = match fld.cx.syntax_env.find(extname) {
@@ -441,18 +456,6 @@ pub fn expand_item_mac(it: P<ast::Item>,
                     let allow_internal_unstable = attr::contains_name(&attrs,
                                                                       "allow_internal_unstable");
 
-                    // ensure any #[allow_internal_unstable]s are
-                    // detected (including nested macro definitions
-                    // etc.)
-                    if allow_internal_unstable && !fld.cx.ecfg.enable_allow_internal_unstable() {
-                        feature_gate::emit_feature_err(
-                            &fld.cx.parse_sess.span_diagnostic,
-                            "allow_internal_unstable",
-                            span,
-                            feature_gate::GateIssue::Language,
-                            feature_gate::EXPLAIN_ALLOW_INTERNAL_UNSTABLE)
-                    }
-
                     let export = attr::contains_name(&attrs, "macro_export");
                     let def = ast::MacroDef {
                         ident: ident,
@@ -516,6 +519,10 @@ fn expand_stmt(stmt: Stmt, fld: &mut MacroExpander) -> SmallVector<Stmt> {
         _ => return expand_non_macro_stmt(stmt, fld)
     };
 
+    if let Some(ref attrs) = attrs {
+        check_attributes(attrs, fld);
+    }
+
     // Assert that we drop any macro attributes on the floor here
     drop(attrs);
 
@@ -1063,7 +1070,7 @@ fn expand_impl_item(ii: ast::ImplItem, fld: &mut MacroExpander)
             attrs: ii.attrs,
             vis: ii.vis,
             defaultness: ii.defaultness,
-            node: match ii.node  {
+            node: match ii.node {
                 ast::ImplItemKind::Method(sig, body) => {
                     let (sig, body) = expand_and_rename_method(sig, body, fld);
                     ast::ImplItemKind::Method(sig, body)
@@ -1072,13 +1079,11 @@ fn expand_impl_item(ii: ast::ImplItem, fld: &mut MacroExpander)
             },
             span: fld.new_span(ii.span)
         }),
-        ast::ImplItemKind::Macro(_) => {
-            let (span, mac) = match ii.node {
-                ast::ImplItemKind::Macro(mac) => (ii.span, mac),
-                _ => unreachable!()
-            };
+        ast::ImplItemKind::Macro(mac) => {
+            check_attributes(&ii.attrs, fld);
+
             let maybe_new_items =
-                expand_mac_invoc(mac, span,
+                expand_mac_invoc(mac, ii.span,
                                  |r| r.make_impl_items(),
                                  |meths, mark| meths.move_map(|m| mark_impl_item(m, mark)),
                                  fld);
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index e281e30dbc2..63fc33e4872 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -688,7 +688,7 @@ pub fn check_for_pushpop_syntax(f: Option<&Features>, diag: &Handler, span: Span
 }
 
 struct Context<'a> {
-    features: Features,
+    features: &'a Features,
     span_handler: &'a Handler,
     cm: &'a CodeMap,
     plugin_attributes: &'a [(String, AttributeType)],
@@ -739,9 +739,7 @@ impl<'a> Context<'a> {
                            with the prefix `rustc_` \
                            are reserved for internal compiler diagnostics");
         } else if name.starts_with("derive_") {
-            gate_feature!(self, custom_derive, attr.span,
-                          "attributes of the form `#[derive_*]` are reserved \
-                           for the compiler");
+            gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
         } else {
             // Only run the custom attribute lint during regular
             // feature gate checking. Macro gating runs
@@ -759,6 +757,15 @@ impl<'a> Context<'a> {
     }
 }
 
+pub fn check_attribute(attr: &ast::Attribute, handler: &Handler,
+                       cm: &CodeMap, features: &Features) {
+    let cx = Context {
+        features: features, span_handler: handler,
+        cm: cm, plugin_attributes: &[]
+    };
+    cx.check_attribute(attr, true);
+}
+
 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
     if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
         let issue = info.2;
@@ -819,64 +826,8 @@ pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
     "`#[derive]` for custom traits is not stable enough for use and is subject to change";
 
-struct MacroVisitor<'a> {
-    context: &'a Context<'a>
-}
-
-impl<'a, 'v> Visitor<'v> for MacroVisitor<'a> {
-    fn visit_mac(&mut self, mac: &ast::Mac) {
-        let path = &mac.node.path;
-        let name = path.segments.last().unwrap().identifier.name.as_str();
-
-        // Issue 22234: If you add a new case here, make sure to also
-        // add code to catch the macro during or after expansion.
-        //
-        // We still keep this MacroVisitor (rather than *solely*
-        // relying on catching cases during or after expansion) to
-        // catch uses of these macros within conditionally-compiled
-        // code, e.g. `#[cfg]`-guarded functions.
-
-        if name == "asm" {
-            gate_feature!(self.context, asm, path.span, EXPLAIN_ASM);
-        }
-
-        else if name == "log_syntax" {
-            gate_feature!(self.context, log_syntax, path.span, EXPLAIN_LOG_SYNTAX);
-        }
-
-        else if name == "trace_macros" {
-            gate_feature!(self.context, trace_macros, path.span, EXPLAIN_TRACE_MACROS);
-        }
-
-        else if name == "concat_idents" {
-            gate_feature!(self.context, concat_idents, path.span, EXPLAIN_CONCAT_IDENTS);
-        }
-    }
-
-    fn visit_attribute(&mut self, attr: &'v ast::Attribute) {
-        self.context.check_attribute(attr, true);
-    }
-
-    fn visit_expr(&mut self, e: &ast::Expr) {
-        // Issue 22181: overloaded-`box` and placement-`in` are
-        // implemented via a desugaring expansion, so their feature
-        // gates go into MacroVisitor since that works pre-expansion.
-        //
-        // Issue 22234: we also check during expansion as well.
-        // But we keep these checks as a pre-expansion check to catch
-        // uses in e.g. conditionalized code.
-
-        if let ast::ExprKind::Box(_) = e.node {
-            gate_feature!(self.context, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
-        }
-
-        if let ast::ExprKind::InPlace(..) = e.node {
-            gate_feature!(self.context, placement_in_syntax, e.span, EXPLAIN_PLACEMENT_IN);
-        }
-
-        visit::walk_expr(self, e);
-    }
-}
+pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
+    "attributes of the form `#[derive_*]` are reserved for the compiler";
 
 struct PostExpansionVisitor<'a> {
     context: &'a Context<'a>,
@@ -1177,13 +1128,7 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
     }
 }
 
-fn check_crate_inner<F>(cm: &CodeMap, span_handler: &Handler,
-                        krate: &ast::Crate,
-                        plugin_attributes: &[(String, AttributeType)],
-                        check: F)
-                       -> Features
-    where F: FnOnce(&mut Context, &ast::Crate)
-{
+pub fn get_features(span_handler: &Handler, krate: &ast::Crate) -> Features {
     let mut features = Features::new();
 
     for attr in &krate.attrs {
@@ -1226,32 +1171,24 @@ fn check_crate_inner<F>(cm: &CodeMap, span_handler: &Handler,
         }
     }
 
-    let mut cx = Context {
-        features: features,
-        span_handler: span_handler,
-        cm: cm,
-        plugin_attributes: plugin_attributes,
-    };
-
-    check(&mut cx, krate);
-    cx.features
-}
-
-pub fn check_crate_macros(cm: &CodeMap, span_handler: &Handler, krate: &ast::Crate)
--> Features {
-    check_crate_inner(cm, span_handler, krate, &[] as &'static [_],
-                      |ctx, krate| visit::walk_crate(&mut MacroVisitor { context: ctx }, krate))
+    features
 }
 
 pub fn check_crate(cm: &CodeMap, span_handler: &Handler, krate: &ast::Crate,
                    plugin_attributes: &[(String, AttributeType)],
-                   unstable: UnstableFeatures) -> Features
-{
+                   unstable: UnstableFeatures) -> Features {
     maybe_stage_features(span_handler, krate, unstable);
-
-    check_crate_inner(cm, span_handler, krate, plugin_attributes,
-                      |ctx, krate| visit::walk_crate(&mut PostExpansionVisitor { context: ctx },
-                                                     krate))
+    let features = get_features(span_handler, krate);
+    {
+        let ctx = Context {
+            features: &features,
+            span_handler: span_handler,
+            cm: cm,
+            plugin_attributes: plugin_attributes,
+        };
+        visit::walk_crate(&mut PostExpansionVisitor { context: &ctx }, krate);
+    }
+    features
 }
 
 #[derive(Clone, Copy)]