Suggest valid crate type if invalid

This adds a suggestion to the `invalid_crate_types` lint.

The suggestion is based on the Levenshtein distance to existing crate
types. If no suggestion is found it will show the lint without any
suggestions.

src/librustc/lint/builtin.rs

@@ -422,6 +422,7 @@ pub enum BuiltinLintDiagnostics {
     ProcMacroDeriveResolutionFallback(Span),
     MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
     ElidedLifetimesInPaths(usize, Span, bool, Span, String),
+    UnknownCrateTypes(Span, String, String),
 }
 
 impl BuiltinLintDiagnostics {
@@ -500,6 +501,14 @@ impl BuiltinLintDiagnostics {
                     Applicability::MachineApplicable
                 );
             }
+            BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
+                db.span_suggestion_with_applicability(
+                    span,
+                    &note,
+                    sugg,
+                    Applicability::MaybeIncorrect
+                );
+            }
         }
     }
 }

src/librustc_driver/driver.rs

@@ -57,6 +57,8 @@ use syntax::ext::base::ExtCtxt;
 use syntax::fold::Folder;
 use syntax::parse::{self, PResult};
 use syntax::util::node_count::NodeCounter;
+use syntax::util::lev_distance::find_best_match_for_name;
+use syntax::symbol::Symbol;
 use syntax_pos::{FileName, hygiene};
 use syntax_ext;
 
@@ -1508,13 +1510,45 @@ pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<c
                     Some(ref n) if *n == "staticlib" => Some(config::CrateType::Staticlib),
                     Some(ref n) if *n == "proc-macro" => Some(config::CrateType::ProcMacro),
                     Some(ref n) if *n == "bin" => Some(config::CrateType::Executable),
-                    Some(_) => {
+                    Some(ref n) => {
+                        let crate_types = vec![
+                            Symbol::intern("rlib"),
+                            Symbol::intern("dylib"),
+                            Symbol::intern("cdylib"),
+                            Symbol::intern("lib"),
+                            Symbol::intern("staticlib"),
+                            Symbol::intern("proc-macro"),
+                            Symbol::intern("bin")
+                        ];
+                        if let ast::MetaItemKind::NameValue(spanned) = a.meta().unwrap().node {
+                            let span = spanned.span;
+                            let lev_candidate = find_best_match_for_name(
+                                crate_types.iter(),
+                                &n.as_str(),
+                                None
+                            );
+                            if let Some(candidate) = lev_candidate {
+                                session.buffer_lint_with_diagnostic(
+                                    lint::builtin::UNKNOWN_CRATE_TYPES,
+                                    ast::CRATE_NODE_ID,
+                                    span,
+                                    "invalid `crate_type` value",
+                                    lint::builtin::BuiltinLintDiagnostics::
+                                        UnknownCrateTypes(
+                                            span,
+                                            "did you mean".to_string(),
+                                            format!("\"{}\"", candidate)
+                                        )
+                                );
+                            } else {
                                 session.buffer_lint(
                                     lint::builtin::UNKNOWN_CRATE_TYPES,
                                     ast::CRATE_NODE_ID,
-                            a.span,
-                            "invalid `crate_type` value",
+                                    span,
+                                    "invalid `crate_type` value"
                                 );
+                            }
+                        }
                         None
                     }
                     _ => {

src/test/ui/invalid/invalid-crate-type.rs

@@ -11,6 +11,48 @@
 // regression test for issue 11256
 #![crate_type="foo"]    //~ ERROR invalid `crate_type` value
 
+// Tests for suggestions (#53958)
+
+#![crate_type="statoclib"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION staticlib
+
+#![crate_type="procmacro"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION proc-macro
+
+#![crate_type="static-lib"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION staticlib
+
+#![crate_type="drylib"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION dylib
+
+#![crate_type="dlib"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION rlib
+
+#![crate_type="lob"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION lib
+
+#![crate_type="bon"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION bin
+
+#![crate_type="cdalib"]
+//~^ ERROR invalid `crate_type` value
+//~| HELP did you mean
+//~| SUGGESTION cdylib
+
 fn main() {
     return
 }

src/test/ui/invalid/invalid-crate-type.stderr

@@ -1,10 +1,58 @@
 error: invalid `crate_type` value
-  --> $DIR/invalid-crate-type.rs:12:1
+  --> $DIR/invalid-crate-type.rs:12:15
    |
 LL | #![crate_type="foo"]    //~ ERROR invalid `crate_type` value
-   | ^^^^^^^^^^^^^^^^^^^^
+   |               ^^^^^
    |
    = note: #[deny(unknown_crate_types)] on by default
 
-error: aborting due to previous error
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:16:15
+   |
+LL | #![crate_type="statoclib"]
+   |               ^^^^^^^^^^^ help: did you mean: `"staticlib"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:21:15
+   |
+LL | #![crate_type="procmacro"]
+   |               ^^^^^^^^^^^ help: did you mean: `"proc-macro"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:26:15
+   |
+LL | #![crate_type="static-lib"]
+   |               ^^^^^^^^^^^^ help: did you mean: `"staticlib"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:31:15
+   |
+LL | #![crate_type="drylib"]
+   |               ^^^^^^^^ help: did you mean: `"dylib"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:36:15
+   |
+LL | #![crate_type="dlib"]
+   |               ^^^^^^ help: did you mean: `"rlib"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:41:15
+   |
+LL | #![crate_type="lob"]
+   |               ^^^^^ help: did you mean: `"lib"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:46:15
+   |
+LL | #![crate_type="bon"]
+   |               ^^^^^ help: did you mean: `"bin"`
+
+error: invalid `crate_type` value
+  --> $DIR/invalid-crate-type.rs:51:15
+   |
+LL | #![crate_type="cdalib"]
+   |               ^^^^^^^^ help: did you mean: `"cdylib"`
+
+error: aborting due to 9 previous errors