Rollup merge of #47481 - estebank:unused-args, r=arielb1

Point at unused arguments for format string

Avoid overlapping spans by only pointing at the arguments that are not
being used in the argument string. Enable libsyntax to have diagnostics
with multiple primary spans by accepting `Into<MultiSpan>` instead of
`Span`.

Partially addresses #41850.

4 files changed, 30 insertions, 39 deletions

diff --git a/src/test/ui/macros/format-foreign.rs b/src/test/ui/macros/format-foreign.rs
index 91ca8f5ff76..ec0eaed43ae 100644
--- a/src/test/ui/macros/format-foreign.rs
+++ b/src/test/ui/macros/format-foreign.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 fn main() {
-    println!("%.*3$s %s!\n", "Hello,", "World", 4);
+    println!("%.*3$s %s!\n", "Hello,", "World", 4); //~ ERROR multiple unused formatting arguments
     println!("%1$*2$.*3$f", 123.456); //~ ERROR never used
 
     // This should *not* produce hints, on the basis that there's equally as
diff --git a/src/test/ui/macros/format-foreign.stderr b/src/test/ui/macros/format-foreign.stderr
index d0229957b68..f9852c54773 100644
--- a/src/test/ui/macros/format-foreign.stderr
+++ b/src/test/ui/macros/format-foreign.stderr
@@ -1,12 +1,8 @@
 error: multiple unused formatting arguments
-  --> $DIR/format-foreign.rs:12:5
+  --> $DIR/format-foreign.rs:12:30
    |
-12 |     println!("%.*3$s %s!/n", "Hello,", "World", 4);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^--------^^-------^^-^^
-   |                              |         |        |
-   |                              |         |        unused
-   |                              |         unused
-   |                              unused
+12 |     println!("%.*3$s %s!/n", "Hello,", "World", 4); //~ ERROR multiple unused formatting arguments
+   |     -------------------------^^^^^^^^--^^^^^^^--^-- multiple unused arguments in this statement
    |
    = help: `%.*3$s` should be written as `{:.2$}`
    = help: `%s` should be written as `{}`
diff --git a/src/test/ui/macros/format-unused-lables.rs b/src/test/ui/macros/format-unused-lables.rs
index 7a32d932ba3..3347a1215ce 100644
--- a/src/test/ui/macros/format-unused-lables.rs
+++ b/src/test/ui/macros/format-unused-lables.rs
@@ -10,9 +10,10 @@
 
 fn main() {
     println!("Test", 123, 456, 789);
+    //~^ ERROR multiple unused formatting arguments
 
     println!("Test2",
-        123,
+        123,  //~ ERROR multiple unused formatting arguments
         456,
         789
     );
@@ -20,7 +21,7 @@ fn main() {
     println!("Some stuff", UNUSED="args"); //~ ERROR named argument never used
 
     println!("Some more $STUFF",
-        "woo!",
+        "woo!",  //~ ERROR multiple unused formatting arguments
             STUFF=
        "things"
              , UNUSED="args");
diff --git a/src/test/ui/macros/format-unused-lables.stderr b/src/test/ui/macros/format-unused-lables.stderr
index 9efdca12dea..64ea5626c1d 100644
--- a/src/test/ui/macros/format-unused-lables.stderr
+++ b/src/test/ui/macros/format-unused-lables.stderr
@@ -1,49 +1,43 @@
 error: multiple unused formatting arguments
-  --> $DIR/format-unused-lables.rs:12:5
+  --> $DIR/format-unused-lables.rs:12:22
    |
 12 |     println!("Test", 123, 456, 789);
-   |     ^^^^^^^^^^^^^^^^^---^^---^^---^^
-   |                      |    |    |
-   |                      |    |    unused
-   |                      |    unused
-   |                      unused
+   |     -----------------^^^--^^^--^^^-- multiple unused arguments in this statement
    |
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: multiple unused formatting arguments
-  --> $DIR/format-unused-lables.rs:14:5
+  --> $DIR/format-unused-lables.rs:16:9
    |
-14 | /     println!("Test2",
-15 | |         123,
-   | |         --- unused
-16 | |         456,
-   | |         --- unused
-17 | |         789
-   | |         --- unused
-18 | |     );
-   | |______^
+15 | /     println!("Test2",
+16 | |         123,  //~ ERROR multiple unused formatting arguments
+   | |         ^^^
+17 | |         456,
+   | |         ^^^
+18 | |         789
+   | |         ^^^
+19 | |     );
+   | |______- multiple unused arguments in this statement
    |
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: named argument never used
-  --> $DIR/format-unused-lables.rs:20:35
+  --> $DIR/format-unused-lables.rs:21:35
    |
-20 |     println!("Some stuff", UNUSED="args"); //~ ERROR named argument never used
+21 |     println!("Some stuff", UNUSED="args"); //~ ERROR named argument never used
    |                                   ^^^^^^
 
 error: multiple unused formatting arguments
-  --> $DIR/format-unused-lables.rs:22:5
+  --> $DIR/format-unused-lables.rs:24:9
    |
-22 | /     println!("Some more $STUFF",
-23 | |         "woo!",
-   | |         ------ unused
-24 | |             STUFF=
-25 | |        "things"
-   | |        -------- unused
-26 | |              , UNUSED="args");
-   | |_______________________------_^
-   |                         |
-   |                         unused
+23 | /     println!("Some more $STUFF",
+24 | |         "woo!",  //~ ERROR multiple unused formatting arguments
+   | |         ^^^^^^
+25 | |             STUFF=
+26 | |        "things"
+   | |        ^^^^^^^^
+27 | |              , UNUSED="args");
+   | |_______________________^^^^^^_- multiple unused arguments in this statement
    |
    = help: `$STUFF` should be written as `{STUFF}`
    = note: shell formatting not supported; see the documentation for `std::fmt`