Auto merge of #56999 - petrochenkov:macrecov2, r=estebank

AST/HIR: Introduce `ExprKind::Err` for better error recovery in the front-end

This way we can avoid aborting compilation if expansion produces errors and generate `ExprKind::Err`s instead.

9 files changed, 7 insertions, 16 deletions

diff --git a/src/libsyntax_ext/asm.rs b/src/libsyntax_ext/asm.rs
index b781e0203e4..a8f3c40db60 100644
--- a/src/libsyntax_ext/asm.rs
+++ b/src/libsyntax_ext/asm.rs
@@ -49,7 +49,6 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt,
                                        sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_ASM);
-        return DummyResult::expr(sp);
     }
 
     // Split the tts before the first colon, to avoid `asm!("x": y)`  being
diff --git a/src/libsyntax_ext/concat_idents.rs b/src/libsyntax_ext/concat_idents.rs
index e2375c6cc19..9c49a59678f 100644
--- a/src/libsyntax_ext/concat_idents.rs
+++ b/src/libsyntax_ext/concat_idents.rs
@@ -20,7 +20,6 @@ pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt,
                                        sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_CONCAT_IDENTS);
-        return base::DummyResult::expr(sp);
     }
 
     if tts.is_empty() {
diff --git a/src/libsyntax_ext/deriving/default.rs b/src/libsyntax_ext/deriving/default.rs
index c26c4bb6274..32d02bec798 100644
--- a/src/libsyntax_ext/deriving/default.rs
+++ b/src/libsyntax_ext/deriving/default.rs
@@ -3,7 +3,7 @@ use deriving::generic::*;
 use deriving::generic::ty::*;
 
 use syntax::ast::{Expr, MetaItem};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax::ext::base::{Annotatable, DummyResult, ExtCtxt};
 use syntax::ext::build::AstBuilder;
 use syntax::ptr::P;
 use syntax::symbol::Symbol;
@@ -69,7 +69,7 @@ fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructur
             span_err!(cx, trait_span, E0665,
                       "`Default` cannot be derived for enums, only structs");
             // let compilation continue
-            cx.expr_usize(trait_span, 0)
+            DummyResult::raw_expr(trait_span, true)
         }
         _ => cx.span_bug(trait_span, "Non-static method in `derive(Default)`"),
     };
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index 85b864dee53..7548d43f184 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -153,6 +153,5 @@ fn call_intrinsic(cx: &ExtCtxt,
         id: ast::DUMMY_NODE_ID,
         rules: ast::BlockCheckMode::Unsafe(ast::CompilerGenerated),
         span,
-        recovered: false,
     }))
 }
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 220765fd8c7..9d29e2b0fb6 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -666,7 +666,7 @@ impl<'a, 'b> Context<'a, 'b> {
                     "X" => "UpperHex",
                     _ => {
                         ecx.span_err(sp, &format!("unknown format trait `{}`", *tyname));
-                        "Dummy"
+                        return DummyResult::raw_expr(sp, true);
                     }
                 }
             }
@@ -713,7 +713,6 @@ pub fn expand_format_args_nl<'cx>(
                                        sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_FORMAT_ARGS_NL);
-        return base::DummyResult::expr(sp);
     }
     sp = sp.apply_mark(ecx.current_expansion.mark);
     match parse_args(ecx, sp, tts) {
@@ -761,7 +760,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
                 Applicability::MaybeIncorrect,
             );
             err.emit();
-            return DummyResult::raw_expr(sp);
+            return DummyResult::raw_expr(sp, true);
         }
     };
 
@@ -857,7 +856,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
             e.span_label(sp, label);
         }
         e.emit();
-        return DummyResult::raw_expr(sp);
+        return DummyResult::raw_expr(sp, true);
     }
 
     let arg_spans = parser.arg_places.iter()
diff --git a/src/libsyntax_ext/global_asm.rs b/src/libsyntax_ext/global_asm.rs
index 16b7ac178be..a58c267ab4f 100644
--- a/src/libsyntax_ext/global_asm.rs
+++ b/src/libsyntax_ext/global_asm.rs
@@ -29,7 +29,6 @@ pub fn expand_global_asm<'cx>(cx: &'cx mut ExtCtxt,
                                        sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_GLOBAL_ASM);
-        return DummyResult::any(sp);
     }
 
     let mut p = cx.new_parser_from_tts(tts);
diff --git a/src/libsyntax_ext/log_syntax.rs b/src/libsyntax_ext/log_syntax.rs
index 5f24ed81cdd..a143186b945 100644
--- a/src/libsyntax_ext/log_syntax.rs
+++ b/src/libsyntax_ext/log_syntax.rs
@@ -14,11 +14,10 @@ pub fn expand_syntax_ext<'cx>(cx: &'cx mut base::ExtCtxt,
                                        sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_LOG_SYNTAX);
-        return base::DummyResult::any(sp);
     }
 
     println!("{}", print::pprust::tts_to_string(tts));
 
     // any so that `log_syntax` can be invoked as an expression and item.
-    base::DummyResult::any(sp)
+    base::DummyResult::any_valid(sp)
 }
diff --git a/src/libsyntax_ext/test_case.rs b/src/libsyntax_ext/test_case.rs
index c467370eed3..04e33671872 100644
--- a/src/libsyntax_ext/test_case.rs
+++ b/src/libsyntax_ext/test_case.rs
@@ -31,8 +31,6 @@ pub fn expand(
                                        attr_sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_CUSTOM_TEST_FRAMEWORKS);
-
-        return vec![anno_item];
     }
 
     if !ecx.ecfg.should_test { return vec![]; }
diff --git a/src/libsyntax_ext/trace_macros.rs b/src/libsyntax_ext/trace_macros.rs
index f17c6de19d9..638d7b5568b 100644
--- a/src/libsyntax_ext/trace_macros.rs
+++ b/src/libsyntax_ext/trace_macros.rs
@@ -15,7 +15,6 @@ pub fn expand_trace_macros(cx: &mut ExtCtxt,
                                        sp,
                                        feature_gate::GateIssue::Language,
                                        feature_gate::EXPLAIN_TRACE_MACROS);
-        return base::DummyResult::any(sp);
     }
 
     match (tt.len(), tt.first()) {
@@ -28,5 +27,5 @@ pub fn expand_trace_macros(cx: &mut ExtCtxt,
         _ => cx.span_err(sp, "trace_macros! accepts only `true` or `false`"),
     }
 
-    base::DummyResult::any(sp)
+    base::DummyResult::any_valid(sp)
 }