[WIP] Add implicit named arguments for fmt macros

src/libsyntax_ext/format.rs

@@ -445,14 +445,13 @@ impl<'a, 'b> Context<'a, 'b> {
                         self.verify_arg_type(Exact(idx), ty)
                     }
                     None => {
-                        let msg = format!("there is no argument named `{}`", name);
-                        let sp = if self.is_literal {
-                            *self.arg_spans.get(self.curpiece).unwrap_or(&self.fmtsp)
-                        } else {
-                            self.fmtsp
-                        };
-                        let mut err = self.ecx.struct_span_err(sp, &msg[..]);
-                        err.emit();
+                        // Treat this name as implicitly passed named argument
+                        let idx = self.args.len();
+                        self.arg_types.push(Vec::new());
+                        self.arg_unique_types.push(Vec::new());
+                        self.args.push(self.ecx.expr_ident(self.fmtsp, ast::Ident::new(name, self.fmtsp)));
+                        self.names.insert(name, idx);
+                        self.verify_arg_type(Exact(idx), ty)
                     }
                 }
             }

src/test/ui/if/ifmt-bad-arg.rs

@@ -25,10 +25,10 @@ fn main() {
     //~^ ERROR: invalid reference to positional arguments 3, 4 and 5 (there are 3 arguments)
 
     format!("{} {foo} {} {bar} {}", 1, 2, 3);
-    //~^ ERROR: there is no argument named `foo`
-    //~^^ ERROR: there is no argument named `bar`
+    //~^ ERROR: cannot find value `foo` in this scope
+    //~^^ ERROR: cannot find value `bar` in this scope
 
-    format!("{foo}");                //~ ERROR: no argument named `foo`
+    format!("{foo}");                //~ ERROR: cannot find value `foo` in this scope
     format!("", 1, 2);               //~ ERROR: multiple unused formatting arguments
     format!("{}", 1, 2);             //~ ERROR: argument never used
     format!("{1}", 1, 2);            //~ ERROR: argument never used
@@ -43,7 +43,7 @@ fn main() {
     // bad named arguments, #35082
 
     format!("{valuea} {valueb}", valuea=5, valuec=7);
-    //~^ ERROR there is no argument named `valueb`
+    //~^ ERROR cannot find value `valueb` in this scope
     //~^^ ERROR named argument never used
 
     // bad syntax of the format string
@@ -60,7 +60,7 @@ fn main() {
         {foo}
 
     "##);
-    //~^^^ ERROR: there is no argument named `foo`
+    //~^^^^^ ERROR: cannot find value `foo` in this scope
 
     // bad syntax in format string with multiple newlines, #53836
     format!("first number: {}

src/test/ui/if/ifmt-bad-arg.stderr

@@ -58,24 +58,6 @@ LL |     format!("{name} {value} {} {} {} {} {} {}", 0, name=1, value=2);
    |
    = note: positional arguments are zero-based
 
-error: there is no argument named `foo`
-  --> $DIR/ifmt-bad-arg.rs:27:17
-   |
-LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
-   |                 ^^^^^
-
-error: there is no argument named `bar`
-  --> $DIR/ifmt-bad-arg.rs:27:26
-   |
-LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
-   |                          ^^^^^
-
-error: there is no argument named `foo`
-  --> $DIR/ifmt-bad-arg.rs:31:14
-   |
-LL |     format!("{foo}");
-   |              ^^^^^
-
 error: multiple unused formatting arguments
   --> $DIR/ifmt-bad-arg.rs:32:17
    |
@@ -154,12 +136,6 @@ LL |     format!("{foo} {} {}", foo=1, 2);
    |                                |
    |                                named argument
 
-error: there is no argument named `valueb`
-  --> $DIR/ifmt-bad-arg.rs:45:23
-   |
-LL |     format!("{valuea} {valueb}", valuea=5, valuec=7);
-   |                       ^^^^^^^^
-
 error: named argument never used
   --> $DIR/ifmt-bad-arg.rs:45:51
    |
@@ -204,12 +180,6 @@ LL |     format!("foo %s baz", "bar");
    |
    = note: printf formatting not supported; see the documentation for `std::fmt`
 
-error: there is no argument named `foo`
-  --> $DIR/ifmt-bad-arg.rs:60:9
-   |
-LL |         {foo}
-   |         ^^^^^
-
 error: invalid format string: expected `'}'`, found `'t'`
   --> $DIR/ifmt-bad-arg.rs:75:1
    |
@@ -283,6 +253,41 @@ LL |     println!("{5} {:4$} {6:7$}", 1);
    = note: positional arguments are zero-based
    = note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
 
+error[E0425]: cannot find value `foo` in this scope
+  --> $DIR/ifmt-bad-arg.rs:27:13
+   |
+LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `bar` in this scope
+  --> $DIR/ifmt-bad-arg.rs:27:13
+   |
+LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `foo` in this scope
+  --> $DIR/ifmt-bad-arg.rs:31:13
+   |
+LL |     format!("{foo}");
+   |             ^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `valueb` in this scope
+  --> $DIR/ifmt-bad-arg.rs:45:13
+   |
+LL |     format!("{valuea} {valueb}", valuea=5, valuec=7);
+   |             ^^^^^^^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `foo` in this scope
+  --> $DIR/ifmt-bad-arg.rs:58:13
+   |
+LL |       format!(r##"
+   |  _____________^
+LL | |
+LL | |         {foo}
+LL | |
+LL | |     "##);
+   | |_______^ not found in this scope
+
 error[E0308]: mismatched types
   --> $DIR/ifmt-bad-arg.rs:78:32
    |
@@ -303,4 +308,5 @@ LL |     println!("{} {:07$.*} {}", 1, 3.2, 4);
 
 error: aborting due to 35 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0425.
+For more information about an error, try `rustc --explain E0308`.