Fix suggestions given mulitple bad lifetimes

When given multiple lifetimes prior to type parameters in generic
parameters, do not ICE and print the correct suggestion.

Author: dlrobertson

src/librustc_errors/lib.rs

@@ -135,10 +135,11 @@ impl CodeSuggestion {
             if let Some(line) = line_opt {
                 if let Some(lo) = line.char_indices().map(|(i, _)| i).nth(lo) {
                     let hi_opt = hi_opt.and_then(|hi| line.char_indices().map(|(i, _)| i).nth(hi));
-                    buf.push_str(match hi_opt {
-                        Some(hi) => &line[lo..hi],
-                        None => &line[lo..],
-                    });
+                    match hi_opt {
+                        Some(hi) if hi > lo => buf.push_str(&line[lo..hi]),
+                        Some(_) => (),
+                        None => buf.push_str(&line[lo..]),
+                    }
                 }
                 if let None = hi_opt {
                     buf.push('\n');

src/libsyntax/parse/parser.rs

@@ -5234,22 +5234,13 @@ impl<'a> Parser<'a> {
                     kind: ast::GenericParamKind::Lifetime,
                 });
                 if let Some(sp) = seen_ty_param {
-                    let param_span = self.prev_span;
-                    let ate_comma = self.eat(&token::Comma);
-                    let remove_sp = if ate_comma {
-                        param_span.until(self.span)
-                    } else {
-                        last_comma_span.unwrap_or(param_span).to(param_span)
-                    };
-                    bad_lifetime_pos.push(param_span);
-
-                    if let Ok(snippet) = self.sess.source_map().span_to_snippet(param_span) {
+                    let remove_sp = last_comma_span.unwrap_or(self.prev_span).to(self.prev_span);
+                    bad_lifetime_pos.push(self.prev_span);
+                    if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.prev_span) {
                         suggestions.push((remove_sp, String::new()));
-                        suggestions.push((sp.shrink_to_lo(), format!("{}, ", snippet)));
-                    }
-                    if ate_comma {
-                        last_comma_span = Some(self.prev_span);
-                        continue
+                        suggestions.push((
+                            sp.shrink_to_lo(),
+                            format!("{}, ", snippet)));
                     }
                 }
             } else if self.check_ident() {

src/test/ui/lifetime-before-type-params.rs

@@ -0,0 +1,9 @@
+#![allow(unused)]
+fn first<T, 'a, 'b>() {}
+//~^ ERROR lifetime parameters must be declared prior to type parameters
+fn second<'a, T, 'b>() {}
+//~^ ERROR lifetime parameters must be declared prior to type parameters
+fn third<T, U, 'a>() {}
+//~^ ERROR lifetime parameters must be declared prior to type parameters
+fn fourth<'a, T, 'b, U, 'c, V>() {}
+//~^ ERROR lifetime parameters must be declared prior to type parameters

src/test/ui/lifetime-before-type-params.stderr

@@ -0,0 +1,47 @@
+error: lifetime parameters must be declared prior to type parameters
+  --> $DIR/lifetime-before-type-params.rs:2:13
+   |
+LL | fn first<T, 'a, 'b>() {}
+   |             ^^  ^^
+help: move the lifetime parameter prior to the first type parameter
+   |
+LL | fn first<'a, 'b, T>() {}
+   |          ^^^ ^^^ --
+
+error: lifetime parameters must be declared prior to type parameters
+  --> $DIR/lifetime-before-type-params.rs:4:18
+   |
+LL | fn second<'a, T, 'b>() {}
+   |                  ^^
+help: move the lifetime parameter prior to the first type parameter
+   |
+LL | fn second<'a, 'b, T>() {}
+   |               ^^^ --
+
+error: lifetime parameters must be declared prior to type parameters
+  --> $DIR/lifetime-before-type-params.rs:6:16
+   |
+LL | fn third<T, U, 'a>() {}
+   |                ^^
+help: move the lifetime parameter prior to the first type parameter
+   |
+LL | fn third<'a, T, U>() {}
+   |          ^^^    --
+
+error: lifetime parameters must be declared prior to type parameters
+  --> $DIR/lifetime-before-type-params.rs:8:18
+   |
+LL | fn fourth<'a, T, 'b, U, 'c, V>() {}
+   |                  ^^     ^^
+help: move the lifetime parameter prior to the first type parameter
+   |
+LL | fn fourth<'a, 'b, 'c, T, U, V>() {}
+   |               ^^^ ^^^ -- --
+
+error[E0601]: `main` function not found in crate `lifetime_before_type_params`
+   |
+   = note: consider adding a `main` function to `$DIR/lifetime-before-type-params.rs`
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0601`.

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

@@ -16,7 +16,7 @@ LL | struct B<T, 'a, U> { //~ ERROR lifetime parameters must be declared
 help: move the lifetime parameter prior to the first type parameter
    |
 LL | struct B<'a, T, U> { //~ ERROR lifetime parameters must be declared
-   |          ^^^   --
+   |          ^^^ --
 
 error: lifetime parameters must be declared prior to type parameters
   --> $DIR/suggest-move-lifetimes.rs:10:16
@@ -36,7 +36,7 @@ LL | struct D<T, U, 'a, 'b, V, 'c> { //~ ERROR lifetime parameters must be decla
 help: move the lifetime parameter prior to the first type parameter
    |
 LL | struct D<'a, 'b, 'c, T, U, V> { //~ ERROR lifetime parameters must be declared
-   |          ^^^ ^^^ ^^^      ---
+   |          ^^^ ^^^ ^^^    -- --
 
 error: aborting due to 4 previous errors