Rollup merge of #70519 - estebank:constraints-before-args-spans, r=Centril

Tweak output of type params and constraints in the wrong order

r? @Centril @varkor

Cargo.lock

@@ -3564,6 +3564,7 @@ dependencies = [
 name = "rustc_ast_passes"
 version = "0.0.0"
 dependencies = [
+ "itertools 0.8.0",
  "log",
  "rustc_ast",
  "rustc_ast_pretty",

src/librustc_ast/ast.rs

@@ -300,8 +300,8 @@ pub enum GenericBound {
 impl GenericBound {
     pub fn span(&self) -> Span {
         match self {
-            &GenericBound::Trait(ref t, ..) => t.span,
+            GenericBound::Trait(ref t, ..) => t.span,
-            &GenericBound::Outlives(ref l) => l.ident.span,
+            GenericBound::Outlives(ref l) => l.ident.span,
         }
     }
 }

src/librustc_ast_passes/Cargo.toml

@@ -9,6 +9,7 @@ name = "rustc_ast_passes"
 path = "lib.rs"
 
 [dependencies]
+itertools = "0.8"
 log = "0.4"
 rustc_ast_pretty = { path = "../librustc_ast_pretty" }
 rustc_attr = { path = "../librustc_attr" }

src/librustc_ast_passes/ast_validation.rs

@@ -6,6 +6,7 @@
 // This pass is supposed to perform only simple checks not requiring name resolution
 // or type checking or some other kind of complex analysis.
 
+use itertools::{Either, Itertools};
 use rustc_ast::ast::*;
 use rustc_ast::attr;
 use rustc_ast::expand::is_proc_macro_attr;
@@ -14,7 +15,7 @@ use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
 use rustc_ast::walk_list;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{error_code, struct_span_err, Applicability};
+use rustc_errors::{error_code, pluralize, struct_span_err, Applicability};
 use rustc_parse::validate_attr;
 use rustc_session::lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY;
 use rustc_session::lint::LintBuffer;
@@ -640,6 +641,33 @@ impl<'a> AstValidator<'a> {
         }
     }
 
+    fn correct_generic_order_suggestion(&self, data: &AngleBracketedArgs) -> String {
+        // Lifetimes always come first.
+        let lt_sugg = data.args.iter().filter_map(|arg| match arg {
+            AngleBracketedArg::Arg(lt @ GenericArg::Lifetime(_)) => {
+                Some(pprust::to_string(|s| s.print_generic_arg(lt)))
+            }
+            _ => None,
+        });
+        let args_sugg = data.args.iter().filter_map(|a| match a {
+            AngleBracketedArg::Arg(GenericArg::Lifetime(_)) | AngleBracketedArg::Constraint(_) => {
+                None
+            }
+            AngleBracketedArg::Arg(arg) => Some(pprust::to_string(|s| s.print_generic_arg(arg))),
+        });
+        // Constraints always come last.
+        let constraint_sugg = data.args.iter().filter_map(|a| match a {
+            AngleBracketedArg::Arg(_) => None,
+            AngleBracketedArg::Constraint(c) => {
+                Some(pprust::to_string(|s| s.print_assoc_constraint(c)))
+            }
+        });
+        format!(
+            "<{}>",
+            lt_sugg.chain(args_sugg).chain(constraint_sugg).collect::<Vec<String>>().join(", ")
+        )
+    }
+
     /// Enforce generic args coming before constraints in `<...>` of a path segment.
     fn check_generic_args_before_constraints(&self, data: &AngleBracketedArgs) {
         // Early exit in case it's partitioned as it should be.
@@ -647,24 +675,36 @@ impl<'a> AstValidator<'a> {
             return;
         }
         // Find all generic argument coming after the first constraint...
-        let mut misplaced_args = Vec::new();
+        let (constraint_spans, arg_spans): (Vec<Span>, Vec<Span>) =
-        let mut first = None;
+            data.args.iter().partition_map(|arg| match arg {
-        for arg in &data.args {
+                AngleBracketedArg::Constraint(c) => Either::Left(c.span),
-            match (arg, first) {
+                AngleBracketedArg::Arg(a) => Either::Right(a.span()),
-                (AngleBracketedArg::Arg(a), Some(_)) => misplaced_args.push(a.span()),
+            });
-                (AngleBracketedArg::Constraint(c), None) => first = Some(c.span),
+        let args_len = arg_spans.len();
-                (AngleBracketedArg::Arg(_), None) | (AngleBracketedArg::Constraint(_), Some(_)) => {
+        let constraint_len = constraint_spans.len();
-                }
-            }
-        }
         // ...and then error:
         self.err_handler()
             .struct_span_err(
-                misplaced_args.clone(),
+                arg_spans.clone(),
                 "generic arguments must come before the first constraint",
             )
-            .span_label(first.unwrap(), "the first constraint is provided here")
+            .span_label(constraint_spans[0], &format!("constraint{}", pluralize!(constraint_len)))
-            .span_labels(misplaced_args, "generic argument")
+            .span_label(
+                *arg_spans.iter().last().unwrap(),
+                &format!("generic argument{}", pluralize!(args_len)),
+            )
+            .span_labels(constraint_spans, "")
+            .span_labels(arg_spans, "")
+            .span_suggestion_verbose(
+                data.span,
+                &format!(
+                    "move the constraint{} after the generic argument{}",
+                    pluralize!(constraint_len),
+                    pluralize!(args_len)
+                ),
+                self.correct_generic_order_suggestion(&data),
+                Applicability::MachineApplicable,
+            )
             .emit();
     }
 }

src/librustc_ast_pretty/pprust.rs

@@ -869,7 +869,7 @@ impl<'a> State<'a> {
         }
     }
 
-    fn print_assoc_constraint(&mut self, constraint: &ast::AssocTyConstraint) {
+    pub fn print_assoc_constraint(&mut self, constraint: &ast::AssocTyConstraint) {
         self.print_ident(constraint.ident);
         self.s.space();
         match &constraint.kind {
@@ -883,7 +883,7 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_generic_arg(&mut self, generic_arg: &GenericArg) {
+    pub fn print_generic_arg(&mut self, generic_arg: &GenericArg) {
         match generic_arg {
             GenericArg::Lifetime(lt) => self.print_lifetime(*lt),
             GenericArg::Type(ty) => self.print_type(ty),

src/librustc_errors/diagnostic_builder.rs

@@ -315,6 +315,20 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    pub fn span_suggestion_verbose(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestion: String,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.0.allow_suggestions {
+            return self;
+        }
+        self.0.diagnostic.span_suggestion_verbose(sp, msg, suggestion, applicability);
+        self
+    }
+
     pub fn span_suggestion_hidden(
         &mut self,
         sp: Span,

src/test/ui/parser/issue-32214.stderr

@@ -4,7 +4,12 @@ error: generic arguments must come before the first constraint
 LL | pub fn test<W, I: Trait<Item=(), W> >() {}
    |                         -------  ^ generic argument
    |                         |
-   |                         the first constraint is provided here
+   |                         constraint
+   |
+help: move the constraint after the generic argument
+   |
+LL | pub fn test<W, I: Trait<W, Item = ()> >() {}
+   |                        ^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/suggestions/suggest-move-types.stderr

@@ -4,79 +4,103 @@ error: generic arguments must come before the first constraint
 LL | struct A<T, M: One<A=(), T>> {
    |                    ----  ^ generic argument
    |                    |
-   |                    the first constraint is provided here
+   |                    constraint
+   |
+help: move the constraint after the generic argument
+   |
+LL | struct A<T, M: One<T, A = ()>> {
+   |                   ^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
   --> $DIR/suggest-move-types.rs:33:43
    |
 LL | struct Al<'a, T, M: OneWithLifetime<A=(), T, 'a>> {
-   |                                     ----  ^  ^^ generic argument
+   |                                     ----  ^  ^^ generic arguments
-   |                                     |     |
+   |                                     |
-   |                                     |     generic argument
+   |                                     constraint
-   |                                     the first constraint is provided here
+   |
+help: move the constraint after the generic arguments
+   |
+LL | struct Al<'a, T, M: OneWithLifetime<'a, T, A = ()>> {
+   |                                    ^^^^^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
   --> $DIR/suggest-move-types.rs:40:46
    |
 LL | struct B<T, U, V, M: Three<A=(), B=(), C=(), T, U, V>> {
-   |                            ----              ^  ^  ^ generic argument
+   |                            ----  ----  ----  ^  ^  ^ generic arguments
-   |                            |                 |  |
+   |                            |
-   |                            |                 |  generic argument
+   |                            constraints
-   |                            |                 generic argument
+   |
-   |                            the first constraint is provided here
+help: move the constraints after the generic arguments
+   |
+LL | struct B<T, U, V, M: Three<T, U, V, A = (), B = (), C = ()>> {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
   --> $DIR/suggest-move-types.rs:48:71
    |
 LL | struct Bl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<A=(), B=(), C=(), T, U, V, 'a, 'b, 'c>> {
-   |                                                     ----              ^  ^  ^  ^^  ^^  ^^ generic argument
+   |                                                     ----  ----  ----  ^  ^  ^  ^^  ^^  ^^ generic arguments
-   |                                                     |                 |  |  |  |   |
+   |                                                     |
-   |                                                     |                 |  |  |  |   generic argument
+   |                                                     constraints
-   |                                                     |                 |  |  |  generic argument
+   |
-   |                                                     |                 |  |  generic argument
+help: move the constraints after the generic arguments
-   |                                                     |                 |  generic argument
+   |
-   |                                                     |                 generic argument
+LL | struct Bl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<'a, 'b, 'c, T, U, V, A = (), B = (), C = ()>> {
-   |                                                     the first constraint is provided here
+   |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
-  --> $DIR/suggest-move-types.rs:57:49
+  --> $DIR/suggest-move-types.rs:57:28
    |
 LL | struct C<T, U, V, M: Three<T, A=(), B=(), C=(), U, V>> {
-   |                               ----              ^  ^ generic argument
+   |                            ^  ----  ----  ----  ^  ^ generic arguments
-   |                               |                 |
+   |                               |
-   |                               |                 generic argument
+   |                               constraints
-   |                               the first constraint is provided here
+   |
+help: move the constraints after the generic arguments
+   |
+LL | struct C<T, U, V, M: Three<T, U, V, A = (), B = (), C = ()>> {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
-  --> $DIR/suggest-move-types.rs:65:78
+  --> $DIR/suggest-move-types.rs:65:53
    |
 LL | struct Cl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<T, 'a, A=(), B=(), C=(), U, 'b, V, 'c>> {
-   |                                                            ----              ^  ^^  ^  ^^ generic argument
+   |                                                     ^  ^^  ----  ----  ----  ^  ^^  ^  ^^ generic arguments
-   |                                                            |                 |  |   |
+   |                                                            |
-   |                                                            |                 |  |   generic argument
+   |                                                            constraints
-   |                                                            |                 |  generic argument
+   |
-   |                                                            |                 generic argument
+help: move the constraints after the generic arguments
-   |                                                            the first constraint is provided here
+   |
+LL | struct Cl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<'a, 'b, 'c, T, U, V, A = (), B = (), C = ()>> {
+   |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
-  --> $DIR/suggest-move-types.rs:74:43
+  --> $DIR/suggest-move-types.rs:74:28
    |
 LL | struct D<T, U, V, M: Three<T, A=(), B=(), U, C=(), V>> {
-   |                               ----        ^        ^ generic argument
+   |                            ^  ----  ----  ^  ----  ^ generic arguments
-   |                               |           |
+   |                               |
-   |                               |           generic argument
+   |                               constraints
-   |                               the first constraint is provided here
+   |
+help: move the constraints after the generic arguments
+   |
+LL | struct D<T, U, V, M: Three<T, U, V, A = (), B = (), C = ()>> {
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: generic arguments must come before the first constraint
-  --> $DIR/suggest-move-types.rs:82:72
+  --> $DIR/suggest-move-types.rs:82:53
    |
 LL | struct Dl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<T, 'a, A=(), B=(), U, 'b, C=(), V, 'c>> {
-   |                                                            ----        ^  ^^        ^  ^^ generic argument
+   |                                                     ^  ^^  ----  ----  ^  ^^  ----  ^  ^^ generic arguments
-   |                                                            |           |  |         |
+   |                                                            |
-   |                                                            |           |  |         generic argument
+   |                                                            constraints
-   |                                                            |           |  generic argument
+   |
-   |                                                            |           generic argument
+help: move the constraints after the generic arguments
-   |                                                            the first constraint is provided here
+   |
+LL | struct Dl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<'a, 'b, 'c, T, U, V, A = (), B = (), C = ()>> {
+   |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0747]: type provided when a lifetime was expected
   --> $DIR/suggest-move-types.rs:33:43