Auto merge of #60508 - varkor:const-generics-fold-ct-err, r=petrochenkov

Fix substs issues for const errors

Fixes https://github.com/rust-lang/rust/issues/60503.

src/librustc/ty/subst.rs

@@ -550,17 +550,32 @@ impl<'a, 'gcx, 'tcx> SubstFolder<'a, 'gcx, 'tcx> {
         let opt_ty = self.substs.get(p.idx as usize).map(|k| k.unpack());
         let ty = match opt_ty {
             Some(UnpackedKind::Type(ty)) => ty,
-            _ => {
+            Some(kind) => {
                 let span = self.span.unwrap_or(DUMMY_SP);
                 span_bug!(
                     span,
-                    "Type parameter `{:?}` ({:?}/{}) out of range \
+                    "expected type for `{:?}` ({:?}/{}) but found {:?} \
+                     when substituting (root type={:?}) substs={:?}",
+                    p,
+                    source_ty,
+                    p.idx,
+                    kind,
+                    self.root_ty,
+                    self.substs,
+                );
+            }
+            None => {
+                let span = self.span.unwrap_or(DUMMY_SP);
+                span_bug!(
+                    span,
+                    "type parameter `{:?}` ({:?}/{}) out of range \
                      when substituting (root type={:?}) substs={:?}",
                     p,
                     source_ty,
                     p.idx,
                     self.root_ty,
-                    self.substs);
+                    self.substs,
+                );
             }
         };
 
@@ -570,29 +585,41 @@ impl<'a, 'gcx, 'tcx> SubstFolder<'a, 'gcx, 'tcx> {
     fn const_for_param(
         &self,
         p: ParamConst,
-        source_cn: &'tcx ty::Const<'tcx>
+        source_ct: &'tcx ty::Const<'tcx>
     ) -> &'tcx ty::Const<'tcx> {
         // Look up the const in the substitutions. It really should be in there.
-        let opt_cn = self.substs.get(p.index as usize).map(|k| k.unpack());
-        let cn = match opt_cn {
-            Some(UnpackedKind::Const(cn)) => cn,
-            _ => {
+        let opt_ct = self.substs.get(p.index as usize).map(|k| k.unpack());
+        let ct = match opt_ct {
+            Some(UnpackedKind::Const(ct)) => ct,
+            Some(kind) => {
                 let span = self.span.unwrap_or(DUMMY_SP);
                 span_bug!(
                     span,
-                    "Const parameter `{:?}` ({:?}/{}) out of range \
-                     when substituting (root type={:?}) substs={:?}",
+                    "expected const for `{:?}` ({:?}/{}) but found {:?} \
+                     when substituting substs={:?}",
                     p,
-                    source_cn,
+                    source_ct,
+                    p.index,
+                    kind,
+                    self.substs,
+                );
+            }
+            None => {
+                let span = self.span.unwrap_or(DUMMY_SP);
+                span_bug!(
+                    span,
+                    "const parameter `{:?}` ({:?}/{}) out of range \
+                     when substituting substs={:?}",
+                    p,
+                    source_ct,
                     p.index,
-                    self.root_ty,
                     self.substs,
                 );
             }
         };
 
         // FIXME(const_generics): shift const through binders
-        cn
+        ct
     }
 
     /// It is sometimes necessary to adjust the De Bruijn indices during substitution. This occurs

src/librustc_passes/ast_validation.rs

@@ -21,7 +21,7 @@ use syntax::visit::{self, Visitor};
 use syntax::{span_err, struct_span_err, walk_list};
 use syntax_ext::proc_macro_decls::is_proc_macro_attr;
 use syntax_pos::{Span, MultiSpan};
-use errors::Applicability;
+use errors::{Applicability, FatalError};
 use log::debug;
 
 #[derive(Copy, Clone, Debug)]
@@ -368,6 +368,8 @@ fn validate_generics_order<'a>(
     let mut max_param: Option<ParamKindOrd> = None;
     let mut out_of_order = FxHashMap::default();
     let mut param_idents = vec![];
+    let mut found_type = false;
+    let mut found_const = false;
 
     for (kind, bounds, span, ident) in generics {
         if let Some(ident) = ident {
@@ -381,6 +383,11 @@ fn validate_generics_order<'a>(
             }
             Some(_) | None => *max_param = Some(kind),
         };
+        match kind {
+            ParamKindOrd::Type => found_type = true,
+            ParamKindOrd::Const => found_const = true,
+            _ => {}
+        }
     }
 
     let mut ordered_params = "<".to_string();
@@ -408,8 +415,8 @@ fn validate_generics_order<'a>(
         GenericPosition::Arg => "argument",
     };
 
-    for (param_ord, (max_param, spans)) in out_of_order {
-        let mut err = handler.struct_span_err(spans,
+    for (param_ord, (max_param, spans)) in &out_of_order {
+        let mut err = handler.struct_span_err(spans.clone(),
             &format!(
                 "{} {pos}s must be declared prior to {} {pos}s",
                 param_ord,
@@ -430,6 +437,13 @@ fn validate_generics_order<'a>(
         }
         err.emit();
     }
+
+    // FIXME(const_generics): we shouldn't have to abort here at all, but we currently get ICEs
+    // if we don't. Const parameters and type parameters can currently conflict if they
+    // are out-of-order.
+    if !out_of_order.is_empty() && found_type && found_const {
+        FatalError.raise();
+    }
 }
 
 impl<'a> Visitor<'a> for AstValidator<'a> {

src/librustc_typeck/astconv.rs

@@ -553,7 +553,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
         tcx.intern_substs(&substs)
     }
 
-    /// Given the type/region arguments provided to some path (along with
+    /// Given the type/lifetime/const arguments provided to some path (along with
     /// an implicit `Self`, if this is a trait reference) returns the complete
     /// set of substitutions. This may involve applying defaulted type parameters.
     ///
@@ -678,7 +678,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
                     GenericParamDefKind::Const => {
                         // FIXME(const_generics:defaults)
                         // We've already errored above about the mismatch.
-                        tcx.types.err.into()
+                        tcx.consts.err.into()
                     }
                 }
             },

src/librustc_typeck/check/wfcheck.rs

@@ -421,8 +421,8 @@ fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(
     return_ty: Option<Ty<'tcx>>,
 ) {
     let predicates = fcx.tcx.predicates_of(def_id);
-
     let generics = tcx.generics_of(def_id);
+
     let is_our_default = |def: &ty::GenericParamDef| {
         match def.kind {
             GenericParamDefKind::Type { has_default, .. } => {
@@ -465,6 +465,7 @@ fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(
                 // All regions are identity.
                 fcx.tcx.mk_param_from_def(param)
             }
+
             GenericParamDefKind::Type { .. } => {
                 // If the param has a default,
                 if is_our_default(param) {
@@ -478,25 +479,24 @@ fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(
                 // Mark unwanted params as err.
                 fcx.tcx.types.err.into()
             }
+
             GenericParamDefKind::Const => {
                 // FIXME(const_generics:defaults)
-                fcx.tcx.types.err.into()
+                fcx.tcx.consts.err.into()
             }
         }
     });
+
     // Now we build the substituted predicates.
     let default_obligations = predicates.predicates.iter().flat_map(|&(pred, _)| {
         #[derive(Default)]
         struct CountParams { params: FxHashSet<u32> }
         impl<'tcx> ty::fold::TypeVisitor<'tcx> for CountParams {
             fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
-                match t.sty {
-                    ty::Param(p) => {
-                        self.params.insert(p.idx);
-                        t.super_visit_with(self)
-                    }
-                    _ => t.super_visit_with(self)
+                if let ty::Param(param) = t.sty {
+                    self.params.insert(param.idx);
                 }
+                t.super_visit_with(self)
             }
 
             fn visit_region(&mut self, _: ty::Region<'tcx>) -> bool {

src/test/ui/const-generics/const-param-before-other-params.rs

@@ -1,12 +1,12 @@
 #![feature(const_generics)]
 //~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
-fn foo<const X: (), T>(_: &T) {
-    //~^ ERROR type parameters must be declared prior to const parameters
-}
-
 fn bar<const X: (), 'a>(_: &'a ()) {
     //~^ ERROR lifetime parameters must be declared prior to const parameters
 }
 
+fn foo<const X: (), T>(_: &T) {
+    //~^ ERROR type parameters must be declared prior to const parameters
+}
+
 fn main() {}

src/test/ui/const-generics/const-param-before-other-params.stderr

@@ -4,17 +4,17 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
 
-error: type parameters must be declared prior to const parameters
-  --> $DIR/const-param-before-other-params.rs:4:21
-   |
-LL | fn foo<const X: (), T>(_: &T) {
-   |       --------------^- help: reorder the parameters: lifetimes, then types, then consts: `<T, const X: ()>`
-
 error: lifetime parameters must be declared prior to const parameters
-  --> $DIR/const-param-before-other-params.rs:8:21
+  --> $DIR/const-param-before-other-params.rs:4:21
    |
 LL | fn bar<const X: (), 'a>(_: &'a ()) {
    |       --------------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, const X: ()>`
 
+error: type parameters must be declared prior to const parameters
+  --> $DIR/const-param-before-other-params.rs:8:21
+   |
+LL | fn foo<const X: (), T>(_: &T) {
+   |       --------------^- help: reorder the parameters: lifetimes, then types, then consts: `<T, const X: ()>`
+
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/const-param-in-trait-ungated.rs

@@ -0,0 +1,3 @@
+trait Trait<const T: ()> {} //~ ERROR const generics are unstable
+
+fn main() {}

src/test/ui/const-generics/const-param-in-trait-ungated.stderr

@@ -0,0 +1,12 @@
+error[E0658]: const generics are unstable
+  --> $DIR/const-param-in-trait-ungated.rs:1:19
+   |
+LL | trait Trait<const T: ()> {}
+   |                   ^
+   |
+   = note: for more information, see https://github.com/rust-lang/rust/issues/44580
+   = help: add #![feature(const_generics)] to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.

src/test/ui/const-generics/const-param-in-trait.rs

@@ -0,0 +1,8 @@
+// run-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+trait Trait<const T: ()> {}
+
+fn main() {}

src/test/ui/const-generics/const-param-in-trait.stderr

@@ -0,0 +1,6 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/const-param-in-trait.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+