add test for issue 69020

Author: RalfJung

src/test/ui/consts/issue-69020.default.stderr

@@ -0,0 +1,10 @@
+error: this arithmetic operation will overflow
+  --> $DIR/issue-69020.rs:15:20
+   |
+LL |     const N: i32 = -i32::MIN + T::N;
+   |                    ^^^^^^^^^ attempt to negate with overflow
+   |
+   = note: `#[deny(overflow)]` on by default
+
+error: aborting due to previous error
+

src/test/ui/consts/issue-69020.noopt.stderr

@@ -0,0 +1,10 @@
+error: this arithmetic operation will overflow
+  --> $DIR/issue-69020.rs:15:20
+   |
+LL |     const N: i32 = -i32::MIN + T::N;
+   |                    ^^^^^^^^^ attempt to negate with overflow
+   |
+   = note: `#[deny(overflow)]` on by default
+
+error: aborting due to previous error
+

src/test/ui/consts/issue-69020.opt.stderr

@@ -0,0 +1,10 @@
+error: this arithmetic operation will overflow
+  --> $DIR/issue-69020.rs:15:20
+   |
+LL |     const N: i32 = -i32::MIN + T::N;
+   |                    ^^^^^^^^^ attempt to negate with overflow
+   |
+   = note: `#[deny(overflow)]` on by default
+
+error: aborting due to previous error
+

src/test/ui/consts/issue-69020.opt_with_overflow_checks.stderr

@@ -0,0 +1,10 @@
+error: this arithmetic operation will overflow
+  --> $DIR/issue-69020.rs:15:20
+   |
+LL |     const N: i32 = -i32::MIN + T::N;
+   |                    ^^^^^^^^^ attempt to negate with overflow
+   |
+   = note: `#[deny(overflow)]` on by default
+
+error: aborting due to previous error
+

src/test/ui/consts/issue-69020.rs

@@ -0,0 +1,17 @@
+// revisions: default noopt opt opt_with_overflow_checks
+//[noopt]compile-flags: -C opt-level=0
+//[opt]compile-flags: -O
+//[opt_with_overflow_checks]compile-flags: -C overflow-checks=on -O
+
+#![crate_type="lib"]
+
+use std::i32;
+
+pub trait Foo {
+    const N: i32;
+}
+
+impl<T: Foo> Foo for Vec<T> {
+    const N: i32 = -i32::MIN + T::N;
+    //~^ ERROR arithmetic operation will overflow
+}