make simple check of prinf function.

With this commit we start to make some simple
check when the name resolution fails, and
we generate some helper message in case the
name is a C name like in the case of the `printf`
and suggest the correct rust method.

Signed-off-by: Vincenzo Palazzo <[email protected]>

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -282,6 +282,14 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                             "you may want to use a bool value instead",
                             format!("{}", item_typo),
                         ))
+                    // FIXME(vicnenzopalazzo): make the check smarter,
+                    // and maybe expand with levenshtein distance checks
+                    } else if item_str.as_str() == "printf" {
+                        Some((
+                            item_span,
+                            "you may have meant to use the `print` macro",
+                            "print!".to_owned(),
+                        ))
                     } else {
                         suggestion
                     };

src/test/ui/suggestions/seggest_print_over_printf.rs

@@ -0,0 +1,9 @@
+// Suggest to a user to use the print macros
+// instead to use the printf.
+
+fn main() {
+    let x = 4;
+    printf("%d", x);
+    //~^ ERROR cannot find function `printf` in this scope
+    //~| HELP you may have meant to use the `print` macro
+}

src/test/ui/suggestions/seggest_print_over_printf.stderr

@@ -0,0 +1,14 @@
+error[E0425]: cannot find function `printf` in this scope
+  --> $DIR/seggest_print_over_printf.rs:6:5
+   |
+LL |     printf("%d", x);
+   |     ^^^^^^ not found in this scope
+   |
+help: you may have meant to use the `print` macro
+   |
+LL |     print!("%d", x);
+   |     ~~~~~~
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0425`.