Resolve incorrect diagnostic for using a non-const value in a constant

Author: varkor

src/librustc_resolve/lib.rs

@@ -4164,6 +4164,9 @@ impl<'a> Resolver<'a> {
                 span_bug!(span, "unexpected {:?} in bindings", def)
             }
             Def::Local(node_id) => {
+                use ResolutionError::*;
+                let mut res_err = None;
+
                 for rib in ribs {
                     match rib.kind {
                         NormalRibKind | ModuleRibKind(..) | MacroDefinition(..) |
@@ -4199,21 +4202,26 @@ impl<'a> Resolver<'a> {
                             // named function item. This is not allowed, so we
                             // report an error.
                             if record_used {
-                                resolve_error(self, span,
-                                    ResolutionError::CannotCaptureDynamicEnvironmentInFnItem);
+                                // We don't immediately trigger a resolve error, because
+                                // we want certain other resolution errors (namely those
+                                // emitted for `ConstantItemRibKind` below) to take
+                                // precedence.
+                                res_err = Some(CannotCaptureDynamicEnvironmentInFnItem);
                             }
-                            return Def::Err;
                         }
                         ConstantItemRibKind => {
                             // Still doesn't deal with upvars
                             if record_used {
-                                resolve_error(self, span,
-                                    ResolutionError::AttemptToUseNonConstantValueInConstant);
+                                resolve_error(self, span, AttemptToUseNonConstantValueInConstant);
                             }
                             return Def::Err;
                         }
                     }
                 }
+                if let Some(res_err) = res_err {
+                     resolve_error(self, span, res_err);
+                     return Def::Err;
+                }
             }
             Def::TyParam(..) | Def::SelfTy(..) => {
                 for rib in ribs {

src/test/ui/impl-trait/bindings.rs

@@ -2,27 +2,27 @@
 
 fn a<T: Clone>(x: T) {
     const foo: impl Clone = x;
-//~^ ERROR can't capture dynamic environment in a fn item
+    //~^ ERROR attempt to use a non-constant value in a constant
 }
 
 fn b<T: Clone>(x: T) {
     let _ = move || {
         const foo: impl Clone = x;
-//~^ ERROR can't capture dynamic environment in a fn item
+        //~^ ERROR attempt to use a non-constant value in a constant
     };
 }
 
 trait Foo<T: Clone> {
     fn a(x: T) {
         const foo: impl Clone = x;
-//~^ ERROR can't capture dynamic environment in a fn item
+        //~^ ERROR attempt to use a non-constant value in a constant
     }
 }
 
 impl<T: Clone> Foo<T> for i32 {
     fn a(x: T) {
         const foo: impl Clone = x;
-//~^ ERROR can't capture dynamic environment in a fn item
+        //~^ ERROR attempt to use a non-constant value in a constant
     }
 }
 

src/test/ui/impl-trait/bindings.stderr

@@ -1,35 +1,27 @@
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/bindings.rs:4:29
    |
 LL |     const foo: impl Clone = x;
-   |                             ^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                             ^ non-constant value
 
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/bindings.rs:10:33
    |
 LL |         const foo: impl Clone = x;
-   |                                 ^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                                 ^ non-constant value
 
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/bindings.rs:17:33
    |
 LL |         const foo: impl Clone = x;
-   |                                 ^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                                 ^ non-constant value
 
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/bindings.rs:24:33
    |
 LL |         const foo: impl Clone = x;
-   |                                 ^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                                 ^ non-constant value
 
 error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0434`.
+For more information about this error, try `rustc --explain E0435`.

src/test/ui/issues/issue-27433.rs

@@ -1,5 +1,5 @@
 fn main() {
     let foo = 42u32;
     const FOO : u32 = foo;
-                   //~^ ERROR can't capture dynamic environment
+                   //~^ ERROR attempt to use a non-constant value in a constant
 }

src/test/ui/issues/issue-27433.stderr

@@ -1,11 +1,9 @@
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/issue-27433.rs:3:23
    |
 LL |     const FOO : u32 = foo;
-   |                       ^^^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                       ^^^ non-constant value
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0434`.
+For more information about this error, try `rustc --explain E0435`.

src/test/ui/issues/issue-3521-2.rs

@@ -2,7 +2,7 @@ fn main() {
     let foo = 100;
 
     static y: isize = foo + 1;
-    //~^ ERROR can't capture dynamic environment
+    //~^ ERROR attempt to use a non-constant value in a constant
 
     println!("{}", y);
 }

src/test/ui/issues/issue-3521-2.stderr

@@ -1,11 +1,9 @@
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/issue-3521-2.rs:4:23
    |
 LL |     static y: isize = foo + 1;
-   |                       ^^^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                       ^^^ non-constant value
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0434`.
+For more information about this error, try `rustc --explain E0435`.

src/test/ui/issues/issue-3668-2.rs

@@ -1,6 +1,6 @@
 fn f(x:isize) {
     static child: isize = x + 1;
-    //~^ ERROR can't capture dynamic environment
+    //~^ ERROR attempt to use a non-constant value in a constant
 }
 
 fn main() {}

src/test/ui/issues/issue-3668-2.stderr

@@ -1,11 +1,9 @@
-error[E0434]: can't capture dynamic environment in a fn item
+error[E0435]: attempt to use a non-constant value in a constant
   --> $DIR/issue-3668-2.rs:2:27
    |
 LL |     static child: isize = x + 1;
-   |                           ^
-   |
-   = help: use the `|| { ... }` closure form instead
+   |                           ^ non-constant value
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0434`.
+For more information about this error, try `rustc --explain E0435`.

src/test/ui/issues/issue-3668.rs

@@ -6,7 +6,7 @@ trait PTrait {
 impl PTrait for P {
    fn getChildOption(&self) -> Option<Box<P>> {
        static childVal: Box<P> = self.child.get();
-       //~^ ERROR can't capture dynamic environment
+       //~^ ERROR attempt to use a non-constant value in a constant
        panic!();
    }
 }