From d9d69212c3d1dca7e8975d5163f09289db4a7420 Mon Sep 17 00:00:00 2001
From: Henry Boisdequin <65845077+henryboisdequin@users.noreply.github.com>
Date: Wed, 3 Mar 2021 16:50:07 +0530
Subject: [PATCH] Fix diagnostic suggests adding type `[type error]`

Fixes #79040

Unresolved questions:

Why does this change output the diagnostic twice?

Why does the CI fail when the errors are pointed out (UI tests)?
---
 compiler/rustc_typeck/src/collect/type_of.rs  |  2 +-
 src/test/ui/79040.rs                          |  5 +++++
 src/test/ui/79040.stderr                      | 19 +++++++++++++++++++
 ...em-free-const-no-body-semantic-fail.stderr |  8 +-------
 ...m-free-static-no-body-semantic-fail.stderr | 14 +-------------
 5 files changed, 27 insertions(+), 21 deletions(-)
 create mode 100644 src/test/ui/79040.rs
 create mode 100644 src/test/ui/79040.stderr

diff --git a/compiler/rustc_typeck/src/collect/type_of.rs b/compiler/rustc_typeck/src/collect/type_of.rs
index e4eabca9c3b..92e2b523202 100644
--- a/compiler/rustc_typeck/src/collect/type_of.rs
+++ b/compiler/rustc_typeck/src/collect/type_of.rs
@@ -659,7 +659,7 @@ fn infer_placeholder_type(
                 format!("{}: {}", item_ident, ty),
                 Applicability::MachineApplicable,
             )
-            .emit();
+            .emit_unless(matches!(ty.kind(), ty::Error(_)));
         }
         None => {
             let mut diag = bad_placeholder_type(tcx, vec![span]);
diff --git a/src/test/ui/79040.rs b/src/test/ui/79040.rs
new file mode 100644
index 00000000000..adc9dc8b426
--- /dev/null
+++ b/src/test/ui/79040.rs
@@ -0,0 +1,5 @@
+fn main() {
+    const FOO = "hello" + 1;
+    //^~ ERROR cannot add `{integer}` to `&str`
+    println!("{}", FOO);
+}
\ No newline at end of file
diff --git a/src/test/ui/79040.stderr b/src/test/ui/79040.stderr
new file mode 100644
index 00000000000..be7d2363c2d
--- /dev/null
+++ b/src/test/ui/79040.stderr
@@ -0,0 +1,19 @@
+error[E0369]: cannot add `{integer}` to `&str`
+  --> $DIR/79040.rs:2:25
+   |
+LL |     const FOO = "hello" + 1;
+   |                 ------- ^ - {integer}
+   |                 |
+   |                 &str
+
+error[E0369]: cannot add `{integer}` to `&str`
+  --> $DIR/79040.rs:2:25
+   |
+LL |     const FOO = "hello" + 1;
+   |                 ------- ^ - {integer}
+   |                 |
+   |                 &str
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0369`.
diff --git a/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr b/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr
index 4e97229fa1a..aa75e5cee01 100644
--- a/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr
+++ b/src/test/ui/parser/item-free-const-no-body-semantic-fail.stderr
@@ -14,11 +14,5 @@ LL | const B;
    |        |
    |        help: provide a definition for the constant: `= <expr>;`
 
-error: missing type for `const` item
-  --> $DIR/item-free-const-no-body-semantic-fail.rs:6:7
-   |
-LL | const B;
-   |       ^ help: provide a type for the item: `B: [type error]`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr b/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr
index 60b7bb34c69..2a270c8290f 100644
--- a/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr
+++ b/src/test/ui/parser/item-free-static-no-body-semantic-fail.stderr
@@ -30,17 +30,5 @@ LL | static mut D;
    |             |
    |             help: provide a definition for the static: `= <expr>;`
 
-error: missing type for `static` item
-  --> $DIR/item-free-static-no-body-semantic-fail.rs:6:8
-   |
-LL | static B;
-   |        ^ help: provide a type for the item: `B: [type error]`
-
-error: missing type for `static mut` item
-  --> $DIR/item-free-static-no-body-semantic-fail.rs:10:12
-   |
-LL | static mut D;
-   |            ^ help: provide a type for the item: `D: [type error]`
-
-error: aborting due to 6 previous errors
+error: aborting due to 4 previous errors