Make use of hygiene in AST passes

15 files changed, 298 insertions, 257 deletions

diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 8b0b5a5b7a2..649cc8a2fb5 100644
--- a/src/librustc_interface/passes.rs
+++ b/src/librustc_interface/passes.rs
@@ -233,7 +233,7 @@ pub fn register_plugins<'a>(
         syntax::attr::inject(krate, &sess.parse_sess, &sess.opts.debugging_opts.crate_attr)
     });
 
-    let (mut krate, features) = syntax::config::features(
+    let (krate, features) = syntax::config::features(
         krate,
         &sess.parse_sess,
         sess.edition(),
@@ -268,16 +268,6 @@ pub fn register_plugins<'a>(
         middle::recursion_limit::update_limits(sess, &krate);
     });
 
-    krate = time(sess, "crate injection", || {
-        let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| &**s);
-        let (krate, name) =
-            syntax_ext::standard_library_imports::inject(krate, alt_std_name, sess.edition());
-        if let Some(name) = name {
-            sess.parse_sess.injected_crate_name.set(name);
-        }
-        krate
-    });
-
     let registrars = time(sess, "plugin loading", || {
         plugin::load::load_plugins(
             sess,
@@ -370,6 +360,21 @@ fn configure_and_expand_inner<'a>(
         &resolver_arenas,
     );
     syntax_ext::register_builtin_macros(&mut resolver, sess.edition());
+
+    krate = time(sess, "crate injection", || {
+        let alt_std_name = sess.opts.alt_std_name.as_ref().map(|s| Symbol::intern(s));
+        let (krate, name) = syntax_ext::standard_library_imports::inject(
+            krate,
+            &mut resolver,
+            alt_std_name,
+            sess.edition(),
+        );
+        if let Some(name) = name {
+            sess.parse_sess.injected_crate_name.set(name);
+        }
+        krate
+    });
+
     syntax_ext::plugin_macro_defs::inject(
         &mut krate, &mut resolver, plugin_info.syntax_exts, sess.edition()
     );
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index fe7eae91945..20d281f1e99 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -97,16 +97,6 @@ impl<'a> base::Resolver for Resolver<'a> {
         self.session.next_node_id()
     }
 
-    fn get_module_scope(&mut self, id: NodeId) -> ExpnId {
-        let expn_id = ExpnId::fresh(Some(ExpnData::default(
-            ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, self.session.edition()
-        )));
-        let module = self.module_map[&self.definitions.local_def_id(id)];
-        self.invocation_parent_scopes.insert(expn_id, ParentScope::module(module));
-        self.definitions.set_invocation_parent(expn_id, module.def_id().unwrap().index);
-        expn_id
-    }
-
     fn resolve_dollar_crates(&mut self) {
         hygiene::update_dollar_crate_names(|ctxt| {
             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 3d274af9908..962447e8cf0 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -653,8 +653,6 @@ bitflags::bitflags! {
 pub trait Resolver {
     fn next_node_id(&mut self) -> NodeId;
 
-    fn get_module_scope(&mut self, id: NodeId) -> ExpnId;
-
     fn resolve_dollar_crates(&mut self);
     fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment,
                                             extra_placeholders: &[NodeId]);
diff --git a/src/libsyntax_ext/plugin_macro_defs.rs b/src/libsyntax_ext/plugin_macro_defs.rs
index dbfd8fe98f3..ccdc5bd81a0 100644
--- a/src/libsyntax_ext/plugin_macro_defs.rs
+++ b/src/libsyntax_ext/plugin_macro_defs.rs
@@ -11,7 +11,7 @@ use syntax::source_map::respan;
 use syntax::symbol::sym;
 use syntax::tokenstream::*;
 use syntax_pos::{Span, DUMMY_SP};
-use syntax_pos::hygiene::{ExpnData, ExpnKind, MacroKind};
+use syntax_pos::hygiene::{ExpnData, ExpnKind, AstPass};
 
 use std::mem;
 
@@ -44,7 +44,7 @@ pub fn inject(
     if !named_exts.is_empty() {
         let mut extra_items = Vec::new();
         let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-            ExpnKind::Macro(MacroKind::Attr, sym::plugin), DUMMY_SP, edition,
+            ExpnKind::AstPass(AstPass::PluginMacroDefs), DUMMY_SP, edition,
             [sym::rustc_attrs][..].into(),
         ));
         for (name, ext) in named_exts {
diff --git a/src/libsyntax_ext/proc_macro_harness.rs b/src/libsyntax_ext/proc_macro_harness.rs
index e772eaf8349..1cdaa1190fa 100644
--- a/src/libsyntax_ext/proc_macro_harness.rs
+++ b/src/libsyntax_ext/proc_macro_harness.rs
@@ -3,8 +3,7 @@ use std::mem;
 use smallvec::smallvec;
 use syntax::ast::{self, Ident};
 use syntax::attr;
-use syntax::source_map::{ExpnData, ExpnKind, respan};
-use syntax::ext::base::{ExtCtxt, MacroKind};
+use syntax::ext::base::ExtCtxt;
 use syntax::ext::expand::{AstFragment, ExpansionConfig};
 use syntax::ext::proc_macro::is_proc_macro_attr;
 use syntax::parse::ParseSess;
@@ -12,6 +11,7 @@ use syntax::ptr::P;
 use syntax::symbol::{kw, sym};
 use syntax::visit::{self, Visitor};
 use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::hygiene::AstPass;
 
 struct ProcMacroDerive {
     trait_name: ast::Name,
@@ -308,8 +308,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 
 // Creates a new module which looks like:
 //
-//      #[doc(hidden)]
-//      mod $gensym {
+//      const _: () = {
 //          extern crate proc_macro;
 //
 //          use proc_macro::bridge::client::ProcMacro;
@@ -327,32 +326,29 @@ fn mk_decls(
     custom_attrs: &[ProcMacroDef],
     custom_macros: &[ProcMacroDef],
 ) -> P<ast::Item> {
-    let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-        ExpnKind::Macro(MacroKind::Attr, sym::proc_macro), DUMMY_SP, cx.parse_sess.edition,
-        [sym::rustc_attrs, sym::proc_macro_internals][..].into(),
-    ));
-
-    let hidden = cx.meta_list_item_word(span, sym::hidden);
-    let doc = cx.meta_list(span, sym::doc, vec![hidden]);
-    let doc_hidden = cx.attribute(doc);
-
-    let proc_macro = Ident::with_dummy_span(sym::proc_macro);
+    let span = cx.resolver.span_for_ast_pass(
+        DUMMY_SP,
+        AstPass::ProcMacroHarness,
+        &[sym::rustc_attrs, sym::proc_macro_internals],
+        None,
+    );
+
+    let proc_macro = Ident::new(sym::proc_macro, span);
     let krate = cx.item(span,
                         proc_macro,
                         Vec::new(),
                         ast::ItemKind::ExternCrate(None));
 
-    let bridge = Ident::from_str("bridge");
-    let client = Ident::from_str("client");
-    let proc_macro_ty = Ident::from_str("ProcMacro");
-    let custom_derive = Ident::from_str("custom_derive");
-    let attr = Ident::from_str("attr");
-    let bang = Ident::from_str("bang");
-    let crate_kw = Ident::with_dummy_span(kw::Crate);
+    let bridge = Ident::from_str_and_span("bridge", span);
+    let client = Ident::from_str_and_span("client", span);
+    let proc_macro_ty = Ident::from_str_and_span("ProcMacro", span);
+    let custom_derive = Ident::from_str_and_span("custom_derive", span);
+    let attr = Ident::from_str_and_span("attr", span);
+    let bang = Ident::from_str_and_span("bang", span);
 
     let decls = {
         let local_path = |sp: Span, name| {
-            cx.expr_path(cx.path(sp.with_ctxt(span.ctxt()), vec![crate_kw, name]))
+            cx.expr_path(cx.path(sp.with_ctxt(span.ctxt()), vec![name]))
         };
         let proc_macro_ty_method_path = |method| cx.expr_path(cx.path(span, vec![
             proc_macro, bridge, client, proc_macro_ty, method,
@@ -381,7 +377,7 @@ fn mk_decls(
 
     let decls_static = cx.item_static(
         span,
-        Ident::from_str("_DECLS"),
+        Ident::from_str_and_span("_DECLS", span),
         cx.ty_rptr(span,
             cx.ty(span, ast::TyKind::Slice(
                 cx.ty_path(cx.path(span,
@@ -392,22 +388,44 @@ fn mk_decls(
     ).map(|mut i| {
         let attr = cx.meta_word(span, sym::rustc_proc_macro_decls);
         i.attrs.push(cx.attribute(attr));
-        i.vis = respan(span, ast::VisibilityKind::Public);
         i
     });
 
-    let module = cx.item_mod(
-        span,
+    let block = P(ast::Expr {
+        id: ast::DUMMY_NODE_ID,
+        attrs: syntax::ThinVec::new(),
+        node: ast::ExprKind::Block(P(ast::Block {
+            id: ast::DUMMY_NODE_ID,
+            rules: ast::BlockCheckMode::Default,
+            stmts: vec![
+                ast::Stmt {
+                    id: ast::DUMMY_NODE_ID,
+                    node: ast::StmtKind::Item(krate),
+                    span,
+                },
+                ast::Stmt {
+                    id: ast::DUMMY_NODE_ID,
+                    node: ast::StmtKind::Item(decls_static),
+                    span,
+                }
+            ],
+            span,
+        }), None),
         span,
-        ast::Ident::from_str("decls").gensym(),
-        vec![doc_hidden],
-        vec![krate, decls_static],
-    ).map(|mut i| {
-        i.vis = respan(span, ast::VisibilityKind::Public);
-        i
     });
 
+    let anon_constant = cx.item_const(
+        span,
+        ast::Ident::new(kw::Underscore, span),
+        P(ast::Ty {
+            id: ast::DUMMY_NODE_ID,
+            node: ast::TyKind::Tup(Vec::new()),
+            span,
+        }),
+        block,
+    );
+
     // Integrate the new module into existing module structures.
-    let module = AstFragment::Items(smallvec![module]);
-    cx.monotonic_expander().fully_expand_fragment(module).make_items().pop().unwrap()
+    let items = AstFragment::Items(smallvec![anon_constant]);
+    cx.monotonic_expander().fully_expand_fragment(items).make_items().pop().unwrap()
 }
diff --git a/src/libsyntax_ext/standard_library_imports.rs b/src/libsyntax_ext/standard_library_imports.rs
index 8ca376341fc..61e423266fa 100644
--- a/src/libsyntax_ext/standard_library_imports.rs
+++ b/src/libsyntax_ext/standard_library_imports.rs
@@ -1,52 +1,56 @@
 use syntax::{ast, attr};
 use syntax::edition::Edition;
-use syntax::ext::hygiene::MacroKind;
+use syntax::ext::hygiene::AstPass;
+use syntax::ext::base::Resolver;
 use syntax::ptr::P;
-use syntax::source_map::{ExpnData, ExpnKind, dummy_spanned, respan};
+use syntax::source_map::respan;
 use syntax::symbol::{Ident, Symbol, kw, sym};
 use syntax_pos::DUMMY_SP;
 
-use std::iter;
-
 pub fn inject(
-    mut krate: ast::Crate, alt_std_name: Option<&str>, edition: Edition
+    mut krate: ast::Crate,
+    resolver: &mut dyn Resolver,
+    alt_std_name: Option<Symbol>,
+    edition: Edition,
 ) -> (ast::Crate, Option<Symbol>) {
     let rust_2018 = edition >= Edition::Edition2018;
 
     // the first name in this list is the crate name of the crate with the prelude
-    let names: &[&str] = if attr::contains_name(&krate.attrs, sym::no_core) {
+    let names: &[Symbol] = if attr::contains_name(&krate.attrs, sym::no_core) {
         return (krate, None);
     } else if attr::contains_name(&krate.attrs, sym::no_std) {
         if attr::contains_name(&krate.attrs, sym::compiler_builtins) {
-            &["core"]
+            &[sym::core]
         } else {
-            &["core", "compiler_builtins"]
+            &[sym::core, sym::compiler_builtins]
         }
     } else {
-        &["std"]
+        &[sym::std]
     };
 
+    let span = resolver.span_for_ast_pass(
+        DUMMY_SP,
+        AstPass::StdImports,
+        &[sym::prelude_import],
+        None,
+    );
+
     // .rev() to preserve ordering above in combination with insert(0, ...)
-    let alt_std_name = alt_std_name.map(Symbol::intern);
-    for orig_name_str in names.iter().rev() {
-        // HACK(eddyb) gensym the injected crates on the Rust 2018 edition,
-        // so they don't accidentally interfere with the new import paths.
-        let orig_name_sym = Symbol::intern(orig_name_str);
-        let orig_name_ident = Ident::with_dummy_span(orig_name_sym);
+    for &orig_name_sym in names.iter().rev() {
         let (rename, orig_name) = if rust_2018 {
-            (orig_name_ident.gensym(), Some(orig_name_sym))
+            (Ident::new(kw::Underscore, span), Some(orig_name_sym))
         } else {
-            (orig_name_ident, None)
+            (Ident::with_dummy_span(orig_name_sym), None)
         };
         krate.module.items.insert(0, P(ast::Item {
             attrs: vec![attr::mk_attr_outer(
-                attr::mk_word_item(ast::Ident::with_dummy_span(sym::macro_use))
+                attr::mk_word_item(ast::Ident::new(sym::macro_use, span))
             )],
-            vis: dummy_spanned(ast::VisibilityKind::Inherited),
+            vis: respan(span, ast::VisibilityKind::Inherited),
             node: ast::ItemKind::ExternCrate(alt_std_name.or(orig_name)),
             ident: rename,
             id: ast::DUMMY_NODE_ID,
-            span: DUMMY_SP,
+            span,
             tokens: None,
         }));
     }
@@ -55,24 +59,22 @@ pub fn inject(
     // the prelude.
     let name = names[0];
 
-    let span = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-        ExpnKind::Macro(MacroKind::Attr, sym::std_inject), DUMMY_SP, edition,
-        [sym::prelude_import][..].into(),
-    ));
+    let segments = if rust_2018 {
+        [name, sym::prelude, sym::v1].iter()
+            .map(|symbol| ast::PathSegment::from_ident(ast::Ident::new(*symbol, span)))
+            .collect()
+    } else {
+        [kw::PathRoot, name, sym::prelude, sym::v1].iter()
+            .map(|symbol| ast::PathSegment::from_ident(ast::Ident::with_dummy_span(*symbol)))
+            .collect()
+    };
 
-    krate.module.items.insert(0, P(ast::Item {
+    let use_item = P(ast::Item {
         attrs: vec![attr::mk_attr_outer(
             attr::mk_word_item(ast::Ident::new(sym::prelude_import, span)))],
         vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
         node: ast::ItemKind::Use(P(ast::UseTree {
-            prefix: ast::Path {
-                segments: iter::once(ast::Ident::with_dummy_span(kw::PathRoot))
-                    .chain(
-                        [name, "prelude", "v1"].iter().cloned()
-                            .map(ast::Ident::from_str)
-                    ).map(ast::PathSegment::from_ident).collect(),
-                span,
-            },
+            prefix: ast::Path { segments, span },
             kind: ast::UseTreeKind::Glob,
             span,
         })),
@@ -80,7 +82,65 @@ pub fn inject(
         ident: ast::Ident::invalid(),
         span,
         tokens: None,
-    }));
+    });
+
+    let prelude_import_item = if rust_2018 {
+        let hygienic_extern_crate = P(ast::Item {
+            attrs: vec![],
+            vis: respan(span, ast::VisibilityKind::Inherited),
+            node: ast::ItemKind::ExternCrate(alt_std_name),
+            ident: ast::Ident::new(name, span),
+            id: ast::DUMMY_NODE_ID,
+            span,
+            tokens: None,
+        });
+
+        // Use an anonymous const to hide `extern crate std as hygienic_std`
+        // FIXME: Once inter-crate hygiene exists, this can just be `use_item`.
+        P(ast::Item {
+            attrs: Vec::new(),
+            vis: respan(span.shrink_to_lo(), ast::VisibilityKind::Inherited),
+            node: ast::ItemKind::Const(
+                P(ast::Ty {
+                    id: ast::DUMMY_NODE_ID,
+                    node: ast::TyKind::Tup(Vec::new()),
+                    span,
+                }),
+                P(ast::Expr {
+                    id: ast::DUMMY_NODE_ID,
+                    attrs: syntax::ThinVec::new(),
+                    node: ast::ExprKind::Block(P(ast::Block {
+                        id: ast::DUMMY_NODE_ID,
+                        rules: ast::BlockCheckMode::Default,
+                        stmts: vec![
+                            ast::Stmt {
+                                id: ast::DUMMY_NODE_ID,
+                                node: ast::StmtKind::Item(use_item),
+                                span,
+                            },
+                            ast::Stmt {
+                                id: ast::DUMMY_NODE_ID,
+                                node: ast::StmtKind::Item(hygienic_extern_crate),
+                                span,
+                            }
+                        ],
+                        span,
+                    }), None),
+                    span,
+                })
+            ),
+            id: ast::DUMMY_NODE_ID,
+            ident: ast::Ident::new(kw::Underscore, span),
+            span,
+            tokens: None,
+        })
+    } else {
+        // Have `extern crate std` at the root, so don't need to create a named
+        // extern crate item.
+        use_item
+    };
+
+    krate.module.items.insert(0, prelude_import_item);
 
-    (krate, Some(Symbol::intern(name)))
+    (krate, Some(name))
 }
diff --git a/src/libsyntax_ext/test.rs b/src/libsyntax_ext/test.rs
index 5fd87d3a0e5..be5aca73f5c 100644
--- a/src/libsyntax_ext/test.rs
+++ b/src/libsyntax_ext/test.rs
@@ -28,11 +28,11 @@ pub fn expand_test_case(
 
     if !ecx.ecfg.should_test { return vec![]; }
 
-    let sp = ecx.with_legacy_ctxt(attr_sp);
+    let sp = ecx.with_def_site_ctxt(attr_sp);
     let mut item = anno_item.expect_item();
     item = item.map(|mut item| {
         item.vis = respan(item.vis.span, ast::VisibilityKind::Public);
-        item.ident = item.ident.gensym();
+        item.ident.span = item.ident.span.with_ctxt(sp.ctxt());
         item.attrs.push(
             ecx.attribute(ecx.meta_word(sp, sym::rustc_test_marker))
         );
@@ -92,10 +92,9 @@ pub fn expand_test_or_bench(
         return vec![Annotatable::Item(item)];
     }
 
-    let (sp, attr_sp) = (cx.with_legacy_ctxt(item.span), cx.with_legacy_ctxt(attr_sp));
+    let (sp, attr_sp) = (cx.with_def_site_ctxt(item.span), cx.with_def_site_ctxt(attr_sp));
 
-    // Gensym "test" so we can extern crate without conflicting with any local names
-    let test_id = cx.ident_of("test").gensym();
+    let test_id = ast::Ident::new(sym::test, attr_sp);
 
     // creates test::$name
     let test_path = |name| {
@@ -112,7 +111,7 @@ pub fn expand_test_or_bench(
 
     let test_fn = if is_bench {
         // A simple ident for a lambda
-        let b = cx.ident_of("b");
+        let b = ast::Ident::from_str_and_span("b", attr_sp);
 
         cx.expr_call(sp, cx.expr_path(test_path("StaticBenchFn")), vec![
             // |b| self::test::assert_test_result(
@@ -143,7 +142,7 @@ pub fn expand_test_or_bench(
         ])
     };
 
-    let mut test_const = cx.item(sp, ast::Ident::new(item.ident.name, sp).gensym(),
+    let mut test_const = cx.item(sp, ast::Ident::new(item.ident.name, sp),
         vec![
             // #[cfg(test)]
             cx.attribute(cx.meta_list(attr_sp, sym::cfg, vec![
@@ -192,17 +191,17 @@ pub fn expand_test_or_bench(
         ));
     test_const = test_const.map(|mut tc| { tc.vis.node = ast::VisibilityKind::Public; tc});
 
-    // extern crate test as test_gensym
+    // extern crate test
     let test_extern = cx.item(sp,
         test_id,
         vec![],
-        ast::ItemKind::ExternCrate(Some(sym::test))
+        ast::ItemKind::ExternCrate(None)
     );
 
     log::debug!("synthetic test item:\n{}\n", pprust::item_to_string(&test_const));
 
     vec![
-        // Access to libtest under a gensymed name
+        // Access to libtest under a hygienic name
         Annotatable::Item(test_extern),
         // The generated test case
         Annotatable::Item(test_const),
diff --git a/src/libsyntax_ext/test_harness.rs b/src/libsyntax_ext/test_harness.rs
index 4a6ea0ebf85..6eb132979df 100644
--- a/src/libsyntax_ext/test_harness.rs
+++ b/src/libsyntax_ext/test_harness.rs
@@ -5,32 +5,29 @@ use smallvec::{smallvec, SmallVec};
 use syntax::ast::{self, Ident};
 use syntax::attr;
 use syntax::entry::{self, EntryPointType};
-use syntax::ext::base::{ExtCtxt, MacroKind, Resolver};
+use syntax::ext::base::{ExtCtxt, Resolver};
 use syntax::ext::expand::{AstFragment, ExpansionConfig};
 use syntax::feature_gate::Features;
 use syntax::mut_visit::{*, ExpectOne};
 use syntax::parse::ParseSess;
 use syntax::ptr::P;
-use syntax::source_map::{ExpnData, ExpnKind, dummy_spanned};
-use syntax::symbol::{kw, sym, Symbol};
+use syntax::source_map::respan;
+use syntax::symbol::{sym, Symbol};
 use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::hygiene::{AstPass, SyntaxContext, Transparency};
 
 use std::{iter, mem};
 
 struct Test {
     span: Span,
-    path: Vec<Ident>,
+    ident: Ident,
 }
 
 struct TestCtxt<'a> {
-    span_diagnostic: &'a errors::Handler,
-    path: Vec<Ident>,
     ext_cx: ExtCtxt<'a>,
     test_cases: Vec<Test>,
     reexport_test_harness_main: Option<Symbol>,
     test_runner: Option<ast::Path>,
-    // top-level re-export submodule, filled out after folding is finished
-    toplevel_reexport: Option<Ident>,
 }
 
 // Traverse the crate, collecting all the test functions, eliding any
@@ -43,8 +40,8 @@ pub fn inject(
     span_diagnostic: &errors::Handler,
     features: &Features,
 ) {
-    // Check for #[reexport_test_harness_main = "some_name"] which
-    // creates a `use __test::main as some_name;`. This needs to be
+    // Check for #![reexport_test_harness_main = "some_name"] which gives the
+    // main test function the name `some_name` without hygiene. This needs to be
     // unconditional, so that the attribute is still marked as used in
     // non-test builds.
     let reexport_test_harness_main =
@@ -56,16 +53,13 @@ pub fn inject(
 
     if should_test {
         generate_test_harness(sess, resolver, reexport_test_harness_main,
-                              krate, span_diagnostic, features, test_runner)
+                              krate, features, test_runner)
     }
 }
 
 struct TestHarnessGenerator<'a> {
     cx: TestCtxt<'a>,
-    tests: Vec<Ident>,
-
-    // submodule name, gensym'd identifier for re-exports
-    tested_submods: Vec<(Ident, Ident)>,
+    tests: Vec<Test>,
 }
 
 impl<'a> MutVisitor for TestHarnessGenerator<'a> {
@@ -77,49 +71,46 @@ impl<'a> MutVisitor for TestHarnessGenerator<'a> {
     }
 
     fn flat_map_item(&mut self, i: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
-        let ident = i.ident;
-        if ident.name != kw::Invalid {
-            self.cx.path.push(ident);
-        }
-        debug!("current path: {}", path_name_i(&self.cx.path));
-
         let mut item = i.into_inner();
         if is_test_case(&item) {
             debug!("this is a test item");
 
             let test = Test {
                 span: item.span,
-                path: self.cx.path.clone(),
+                ident: item.ident,
             };
-            self.cx.test_cases.push(test);
-            self.tests.push(item.ident);
+            self.tests.push(test);
         }
 
         // We don't want to recurse into anything other than mods, since
         // mods or tests inside of functions will break things
         if let ast::ItemKind::Mod(mut module) = item.node {
             let tests = mem::take(&mut self.tests);
-            let tested_submods = mem::take(&mut self.tested_submods);
             noop_visit_mod(&mut module, self);
-            let tests = mem::replace(&mut self.tests, tests);
-            let tested_submods = mem::replace(&mut self.tested_submods, tested_submods);
+            let mut tests = mem::replace(&mut self.tests, tests);
 
-            if !tests.is_empty() || !tested_submods.is_empty() {
-                let (it, sym) = mk_reexport_mod(&mut self.cx, item.id, tests, tested_submods);
-                module.items.push(it);
-
-                if !self.cx.path.is_empty() {
-                    self.tested_submods.push((self.cx.path[self.cx.path.len()-1], sym));
+            if !tests.is_empty() {
+                let parent = if item.id == ast::DUMMY_NODE_ID {
+                    ast::CRATE_NODE_ID
                 } else {
-                    debug!("pushing nothing, sym: {:?}", sym);
-                    self.cx.toplevel_reexport = Some(sym);
+                    item.id
+                };
+                // Create an identifier that will hygienically resolve the test
+                // case name, even in another module.
+                let sp = self.cx.ext_cx.resolver.span_for_ast_pass(
+                    module.inner,
+                    AstPass::TestHarness,
+                    &[],
+                    Some(parent),
+                );
+                let expn = sp.ctxt().outer_expn();
+                for test in &mut tests {
+                    test.ident.span = test.ident.span.apply_mark(expn, Transparency::Opaque);
                 }
+                self.cx.test_cases.extend(tests);
             }
             item.node = ast::ItemKind::Mod(module);
         }
-        if ident.name != kw::Invalid {
-            self.cx.path.pop();
-        }
         smallvec![P(item)]
     }
 
@@ -181,59 +172,11 @@ impl MutVisitor for EntryPointCleaner {
     }
 }
 
-/// Creates an item (specifically a module) that "pub use"s the tests passed in.
-/// Each tested submodule will contain a similar reexport module that we will export
-/// under the name of the original module. That is, `submod::__test_reexports` is
-/// reexported like so `pub use submod::__test_reexports as submod`.
-fn mk_reexport_mod(cx: &mut TestCtxt<'_>,
-                   parent: ast::NodeId,
-                   tests: Vec<Ident>,
-                   tested_submods: Vec<(Ident, Ident)>)
-                   -> (P<ast::Item>, Ident) {
-    let super_ = Ident::with_dummy_span(kw::Super);
-
-    let items = tests.into_iter().map(|r| {
-        cx.ext_cx.item_use_simple(DUMMY_SP, dummy_spanned(ast::VisibilityKind::Public),
-                                  cx.ext_cx.path(DUMMY_SP, vec![super_, r]))
-    }).chain(tested_submods.into_iter().map(|(r, sym)| {
-        let path = cx.ext_cx.path(DUMMY_SP, vec![super_, r, sym]);
-        cx.ext_cx.item_use_simple_(DUMMY_SP, dummy_spanned(ast::VisibilityKind::Public),
-                                   Some(r), path)
-    })).collect();
-
-    let reexport_mod = ast::Mod {
-        inline: true,
-        inner: DUMMY_SP,
-        items,
-    };
-
-    let name = Ident::from_str("__test_reexports").gensym();
-    let parent = if parent == ast::DUMMY_NODE_ID { ast::CRATE_NODE_ID } else { parent };
-    cx.ext_cx.current_expansion.id = cx.ext_cx.resolver.get_module_scope(parent);
-    let module = P(ast::Item {
-        ident: name,
-        attrs: Vec::new(),
-        id: ast::DUMMY_NODE_ID,
-        node: ast::ItemKind::Mod(reexport_mod),
-        vis: dummy_spanned(ast::VisibilityKind::Public),
-        span: DUMMY_SP,
-        tokens: None,
-    });
-
-    // Integrate the new module into existing module structures.
-    let module = AstFragment::Items(smallvec![module]);
-    let module =
-        cx.ext_cx.monotonic_expander().fully_expand_fragment(module).make_items().pop().unwrap();
-
-    (module, name)
-}
-
 /// Crawl over the crate, inserting test reexports and the test main function
 fn generate_test_harness(sess: &ParseSess,
                          resolver: &mut dyn Resolver,
                          reexport_test_harness_main: Option<Symbol>,
                          krate: &mut ast::Crate,
-                         sd: &errors::Handler,
                          features: &Features,
                          test_runner: Option<ast::Path>) {
     // Remove the entry points
@@ -244,19 +187,15 @@ fn generate_test_harness(sess: &ParseSess,
     econfig.features = Some(features);
 
     let cx = TestCtxt {
-        span_diagnostic: sd,
         ext_cx: ExtCtxt::new(sess, econfig, resolver),
-        path: Vec::new(),
         test_cases: Vec::new(),
         reexport_test_harness_main,
-        toplevel_reexport: None,
         test_runner
     };
 
     TestHarnessGenerator {
         cx,
         tests: Vec::new(),
-        tested_submods: Vec::new(),
     }.visit_crate(krate);
 }
 
@@ -268,12 +207,14 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     //            #![main]
     //            test::test_main_static(&[..tests]);
     //        }
-    let sp = DUMMY_SP.fresh_expansion(ExpnData::allow_unstable(
-        ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, cx.ext_cx.parse_sess.edition,
-        [sym::main, sym::test, sym::rustc_attrs][..].into(),
-    ));
+    let sp = cx.ext_cx.resolver.span_for_ast_pass(
+        DUMMY_SP,
+        AstPass::TestHarness,
+        &[sym::main, sym::test, sym::rustc_attrs],
+        None,
+    );
     let ecx = &cx.ext_cx;
-    let test_id = Ident::with_dummy_span(sym::test);
+    let test_id = Ident::new(sym::test, sp);
 
     // test::test_main_static(...)
     let mut test_runner = cx.test_runner.clone().unwrap_or(
@@ -285,14 +226,14 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
 
     let test_main_path_expr = ecx.expr_path(test_runner);
     let call_test_main = ecx.expr_call(sp, test_main_path_expr,
-                                       vec![mk_tests_slice(cx)]);
+                                       vec![mk_tests_slice(cx, sp)]);
     let call_test_main = ecx.stmt_expr(call_test_main);
 
     // #![main]
     let main_meta = ecx.meta_word(sp, sym::main);
     let main_attr = ecx.attribute(main_meta);
 
-    // extern crate test as test_gensym
+    // extern crate test
     let test_extern_stmt = ecx.stmt_item(sp, ecx.item(sp,
         test_id,
         vec![],
@@ -316,8 +257,8 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
 
     // Honor the reexport_test_harness_main attribute
     let main_id = match cx.reexport_test_harness_main {
-        Some(sym) => Ident::new(sym, sp),
-        None => Ident::from_str_and_span("main", sp).gensym(),
+        Some(sym) => Ident::new(sym, sp.with_ctxt(SyntaxContext::root())),
+        None => Ident::from_str_and_span("main", sp),
     };
 
     let main = P(ast::Item {
@@ -325,7 +266,7 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
         attrs: vec![main_attr],
         id: ast::DUMMY_NODE_ID,
         node: main,
-        vis: dummy_spanned(ast::VisibilityKind::Public),
+        vis: respan(sp, ast::VisibilityKind::Public),
         span: sp,
         tokens: None,
     });
@@ -335,44 +276,20 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     cx.ext_cx.monotonic_expander().fully_expand_fragment(main).make_items().pop().unwrap()
 }
 
-fn path_name_i(idents: &[Ident]) -> String {
-    let mut path_name = "".to_string();
-    let mut idents_iter = idents.iter().peekable();
-    while let Some(ident) = idents_iter.next() {
-        path_name.push_str(&ident.as_str());
-        if idents_iter.peek().is_some() {
-            path_name.push_str("::")
-        }
-    }
-    path_name
-}
-
 /// Creates a slice containing every test like so:
-/// &[path::to::test1, path::to::test2]
-fn mk_tests_slice(cx: &TestCtxt<'_>) -> P<ast::Expr> {
+/// &[test1, test2]
+fn mk_tests_slice(cx: &TestCtxt<'_>, sp: Span) -> P<ast::Expr> {
     debug!("building test vector from {} tests", cx.test_cases.len());
     let ref ecx = cx.ext_cx;
 
-    ecx.expr_vec_slice(DUMMY_SP,
+
+    ecx.expr_vec_slice(sp,
         cx.test_cases.iter().map(|test| {
             ecx.expr_addr_of(test.span,
-                ecx.expr_path(ecx.path(test.span, visible_path(cx, &test.path))))
+                ecx.expr_path(ecx.path(test.span, vec![test.ident])))
         }).collect())
 }
 
-/// Creates a path from the top-level __test module to the test via __test_reexports
-fn visible_path(cx: &TestCtxt<'_>, path: &[Ident]) -> Vec<Ident>{
-    let mut visible_path = vec![];
-    match cx.toplevel_reexport {
-        Some(id) => visible_path.push(id),
-        None => {
-            cx.span_diagnostic.bug("expected to find top-level re-export name, but found None");
-        }
-    }
-    visible_path.extend_from_slice(path);
-    visible_path
-}
-
 fn is_test_case(i: &ast::Item) -> bool {
     attr::contains_name(&i.attrs, sym::rustc_test_marker)
 }
diff --git a/src/test/ui/hygiene/auxiliary/not-libstd.rs b/src/test/ui/hygiene/auxiliary/not-libstd.rs
new file mode 100644
index 00000000000..babba293d03
--- /dev/null
+++ b/src/test/ui/hygiene/auxiliary/not-libstd.rs
@@ -0,0 +1 @@
+pub fn not_in_lib_std() {}
diff --git a/src/test/ui/hygiene/prelude-import-hygiene.rs b/src/test/ui/hygiene/prelude-import-hygiene.rs
new file mode 100644
index 00000000000..51e7bed6580
--- /dev/null
+++ b/src/test/ui/hygiene/prelude-import-hygiene.rs
@@ -0,0 +1,29 @@
+// Make sure that attribute used when injecting the prelude are resolved
+// hygienically.
+
+// check-pass
+// aux-build:not-libstd.rs
+
+//revisions: rust2015 rust2018
+//[rust2018] edition:2018
+
+// The prelude import shouldn't see these as candidates for when it's trying to
+// use the built-in macros.
+extern crate core;
+use core::prelude::v1::test as prelude_import;
+use core::prelude::v1::test as macro_use;
+
+// Should not be used for the prelude import - not a concern in the 2015 edition
+// because `std` is already declared in the crate root.
+#[cfg(rust2018)]
+extern crate not_libstd as std;
+
+#[cfg(rust2018)]
+mod x {
+    // The extern crate item should override `std` in the extern prelude.
+    fn f() {
+        std::not_in_lib_std();
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/imports/gensymed.rs b/src/test/ui/imports/gensymed.rs
index 613ccc0b242..7b53f0c536a 100644
--- a/src/test/ui/imports/gensymed.rs
+++ b/src/test/ui/imports/gensymed.rs
@@ -1,7 +1,9 @@
-// build-pass (FIXME(62277): could be check-pass?)
+// check-pass
 // edition:2018
 // aux-build:gensymed.rs
 
 extern crate gensymed;
 
+use gensymed::*;
+
 fn main() {}
diff --git a/src/test/ui/inaccessible-test-modules.stderr b/src/test/ui/inaccessible-test-modules.stderr
deleted file mode 100644
index b6a817e6b1d..00000000000
--- a/src/test/ui/inaccessible-test-modules.stderr
+++ /dev/null
@@ -1,21 +0,0 @@
-error[E0432]: unresolved import `__test`
-  --> $DIR/inaccessible-test-modules.rs:5:5
-   |
-LL | use __test as x;
-   |     ------^^^^^
-   |     |
-   |     no `__test` in the root
-   |     help: a similar name exists in the module: `test`
-
-error[E0432]: unresolved import `__test_reexports`
-  --> $DIR/inaccessible-test-modules.rs:6:5
-   |
-LL | use __test_reexports as y;
-   |     ----------------^^^^^
-   |     |
-   |     no `__test_reexports` in the root
-   |     help: a similar name exists in the module: `__test_reexports`
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0432`.
diff --git a/src/test/ui/test-attrs/decl-macro-test.rs b/src/test/ui/test-attrs/decl-macro-test.rs
new file mode 100644
index 00000000000..fcbe9f49e55
--- /dev/null
+++ b/src/test/ui/test-attrs/decl-macro-test.rs
@@ -0,0 +1,22 @@
+// Check that declarative macros can declare tests
+
+// check-pass
+// compile-flags: --test
+
+#![feature(decl_macro)]
+
+macro create_test() {
+    #[test]
+    fn test() {}
+}
+
+macro create_module_test() {
+    mod x {
+        #[test]
+        fn test() {}
+    }
+}
+
+create_test!();
+create_test!();
+create_module_test!();
diff --git a/src/test/ui/inaccessible-test-modules.rs b/src/test/ui/test-attrs/inaccessible-test-modules.rs
index 7095ec290f8..f5b34793794 100644
--- a/src/test/ui/inaccessible-test-modules.rs
+++ b/src/test/ui/test-attrs/inaccessible-test-modules.rs
@@ -2,8 +2,8 @@
 
 // the `--test` harness creates modules with these textual names, but
 // they should be inaccessible from normal code.
-use __test as x; //~ ERROR unresolved import `__test`
-use __test_reexports as y; //~ ERROR unresolved import `__test_reexports`
+use main as x; //~ ERROR unresolved import `main`
+use test as y; //~ ERROR unresolved import `test`
 
 #[test]
 fn baz() {}
diff --git a/src/test/ui/test-attrs/inaccessible-test-modules.stderr b/src/test/ui/test-attrs/inaccessible-test-modules.stderr
new file mode 100644
index 00000000000..a94ea1e79bc
--- /dev/null
+++ b/src/test/ui/test-attrs/inaccessible-test-modules.stderr
@@ -0,0 +1,21 @@
+error[E0432]: unresolved import `main`
+  --> $DIR/inaccessible-test-modules.rs:5:5
+   |
+LL | use main as x;
+   |     ----^^^^^
+   |     |
+   |     no `main` in the root
+   |     help: a similar name exists in the module: `main`
+
+error[E0432]: unresolved import `test`
+  --> $DIR/inaccessible-test-modules.rs:6:5
+   |
+LL | use test as y;
+   |     ----^^^^^
+   |     |
+   |     no `test` in the root
+   |     help: a similar name exists in the module: `test`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0432`.