Auto merge of #47906 - Zoxc:nocycle, r=nikomatsakis

Add a `fatal_cycle` attribute for queries which indicates that they will cause a fatal error on query cycles

This moves us towards the goal of having cycle errors be non-fatal by not relying on the default implementation of `ty::maps::values::Value` which aborts on errors.

r? @nikomatsakis

2 files changed, 27 insertions, 9 deletions

diff --git a/src/librustc/ty/maps/mod.rs b/src/librustc/ty/maps/mod.rs
index 85fca68187f..21ffe6b895e 100644
--- a/src/librustc/ty/maps/mod.rs
+++ b/src/librustc/ty/maps/mod.rs
@@ -78,6 +78,11 @@ pub use self::on_disk_cache::OnDiskCache;
 // a way that memoizes and does dep-graph tracking,
 // wrapping around the actual chain of providers that
 // the driver creates (using several `rustc_*` crates).
+//
+// The result of query must implement Clone. They must also implement ty::maps::values::Value
+// which produces an appropiate error value if the query resulted in a query cycle.
+// Queries marked with `fatal_cycle` do not need that implementation
+// as they will raise an fatal error on query cycles instead.
 define_maps! { <'tcx>
     /// Records the type of every item.
     [] fn type_of: TypeOfItem(DefId) -> Ty<'tcx>,
@@ -267,13 +272,13 @@ define_maps! { <'tcx>
     [] fn dylib_dependency_formats: DylibDepFormats(CrateNum)
                                     -> Rc<Vec<(CrateNum, LinkagePreference)>>,
 
-    [] fn is_panic_runtime: IsPanicRuntime(CrateNum) -> bool,
-    [] fn is_compiler_builtins: IsCompilerBuiltins(CrateNum) -> bool,
-    [] fn has_global_allocator: HasGlobalAllocator(CrateNum) -> bool,
-    [] fn is_sanitizer_runtime: IsSanitizerRuntime(CrateNum) -> bool,
-    [] fn is_profiler_runtime: IsProfilerRuntime(CrateNum) -> bool,
-    [] fn panic_strategy: GetPanicStrategy(CrateNum) -> PanicStrategy,
-    [] fn is_no_builtins: IsNoBuiltins(CrateNum) -> bool,
+    [fatal_cycle] fn is_panic_runtime: IsPanicRuntime(CrateNum) -> bool,
+    [fatal_cycle] fn is_compiler_builtins: IsCompilerBuiltins(CrateNum) -> bool,
+    [fatal_cycle] fn has_global_allocator: HasGlobalAllocator(CrateNum) -> bool,
+    [fatal_cycle] fn is_sanitizer_runtime: IsSanitizerRuntime(CrateNum) -> bool,
+    [fatal_cycle] fn is_profiler_runtime: IsProfilerRuntime(CrateNum) -> bool,
+    [fatal_cycle] fn panic_strategy: GetPanicStrategy(CrateNum) -> PanicStrategy,
+    [fatal_cycle] fn is_no_builtins: IsNoBuiltins(CrateNum) -> bool,
 
     [] fn extern_crate: ExternCrate(DefId) -> Rc<Option<ExternCrate>>,
 
diff --git a/src/librustc/ty/maps/plumbing.rs b/src/librustc/ty/maps/plumbing.rs
index 0ab6ee1a54a..f02c7cbd0ea 100644
--- a/src/librustc/ty/maps/plumbing.rs
+++ b/src/librustc/ty/maps/plumbing.rs
@@ -183,6 +183,19 @@ macro_rules! profq_key {
     }
 }
 
+macro_rules! handle_cycle_error {
+    ([][$this: expr]) => {{
+        Value::from_cycle_error($this.global_tcx())
+    }};
+    ([fatal_cycle$(, $modifiers:ident)*][$this:expr]) => {{
+        $this.tcx.sess.abort_if_errors();
+        unreachable!();
+    }};
+    ([$other:ident$(, $modifiers:ident)*][$($args:tt)*]) => {
+        handle_cycle_error!([$($modifiers),*][$($args)*])
+    };
+}
+
 macro_rules! define_maps {
     (<$tcx:tt>
      $($(#[$attr:meta])*
@@ -564,7 +577,7 @@ macro_rules! define_maps {
             pub fn $name(self, key: $K) -> $V {
                 queries::$name::try_get(self.tcx, self.span, key).unwrap_or_else(|mut e| {
                     e.emit();
-                    Value::from_cycle_error(self.global_tcx())
+                    handle_cycle_error!([$($modifiers)*][self])
                 })
             })*
         }
@@ -583,7 +596,7 @@ macro_rules! define_maps {
 
 macro_rules! define_map_struct {
     (tcx: $tcx:tt,
-     input: ($(([$(modifiers:tt)*] [$($attr:tt)*] [$name:ident]))*)) => {
+     input: ($(([$($modifiers:tt)*] [$($attr:tt)*] [$name:ident]))*)) => {
         pub struct Maps<$tcx> {
             providers: IndexVec<CrateNum, Providers<$tcx>>,
             query_stack: RefCell<Vec<(Span, Query<$tcx>)>>,