Test for const expression missing braces

src/test/ui/const-generics/const-expression-missing-braces.rs

@@ -0,0 +1,26 @@
+#![allow(incomplete_features)]
+#![feature(const_generics)]
+
+fn foo<const C: usize>() {}
+
+fn a() {
+    let bar = 3;
+    foo::<bar + 3>();
+    //~^ ERROR expected one of `!`, `(`, `,`, `>`, `?`, `for`, lifetime, or path, found `3`
+}
+fn b() {
+    let bar = 3;
+    foo::<bar + bar>();
+    //~^ ERROR expected trait, found local variable `bar`
+    //~| ERROR expected trait, found local variable `bar`
+    //~| ERROR wrong number of const arguments: expected 1, found 0
+    //~| ERROR wrong number of type arguments: expected 0, found 1
+    //~| WARNING trait objects without an explicit `dyn` are deprecated
+}
+fn c() {
+    let bar = 3;
+    foo::<3 + 3>();
+    //~^ ERROR expected one of `,` or `>`, found `+`
+}
+
+fn main() {}

src/test/ui/const-generics/const-expression-missing-braces.stderr

@@ -0,0 +1,48 @@
+error: expected one of `!`, `(`, `,`, `>`, `?`, `for`, lifetime, or path, found `3`
+  --> $DIR/const-expression-missing-braces.rs:8:17
+   |
+LL |     foo::<bar + 3>();
+   |                 ^ expected one of 8 possible tokens
+
+error: expected one of `,` or `>`, found `+`
+  --> $DIR/const-expression-missing-braces.rs:22:13
+   |
+LL |     foo::<3 + 3>();
+   |             ^ expected one of `,` or `>`
+
+error[E0404]: expected trait, found local variable `bar`
+  --> $DIR/const-expression-missing-braces.rs:13:11
+   |
+LL |     foo::<bar + bar>();
+   |           ^^^ not a trait
+
+error[E0404]: expected trait, found local variable `bar`
+  --> $DIR/const-expression-missing-braces.rs:13:17
+   |
+LL |     foo::<bar + bar>();
+   |                 ^^^ not a trait
+
+warning: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/const-expression-missing-braces.rs:13:11
+   |
+LL |     foo::<bar + bar>();
+   |           ^^^^^^^^^ help: use `dyn`: `dyn bar + bar`
+   |
+   = note: `#[warn(bare_trait_objects)]` on by default
+
+error[E0107]: wrong number of const arguments: expected 1, found 0
+  --> $DIR/const-expression-missing-braces.rs:13:5
+   |
+LL |     foo::<bar + bar>();
+   |     ^^^^^^^^^^^^^^^^ expected 1 const argument
+
+error[E0107]: wrong number of type arguments: expected 0, found 1
+  --> $DIR/const-expression-missing-braces.rs:13:11
+   |
+LL |     foo::<bar + bar>();
+   |           ^^^^^^^^^ unexpected type argument
+
+error: aborting due to 6 previous errors; 1 warning emitted
+
+Some errors have detailed explanations: E0107, E0404.
+For more information about an error, try `rustc --explain E0107`.