TokenTreesReader now can find the correct mismatch delimiter pairs

compiler/rustc_parse/src/lexer/tokentrees.rs

@@ -3,7 +3,7 @@ use rustc_ast::token::{self, Delimiter, Token};
 use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_ast_pretty::pprust::token_to_string;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{PErr, PResult};
+use rustc_errors::{Diagnostic, PErr, PResult};
 use rustc_span::Span;
 
 pub(super) struct TokenTreesReader<'a> {
@@ -104,22 +104,7 @@ impl<'a> TokenTreesReader<'a> {
         }
 
         if let Some((delim, _)) = self.open_braces.last() {
-            if let Some((_, open_sp, close_sp)) =
-                self.matching_delim_spans.iter().find(|(d, open_sp, close_sp)| {
-                    let sm = self.string_reader.sess.source_map();
-                    if let Some(close_padding) = sm.span_to_margin(*close_sp) {
-                        if let Some(open_padding) = sm.span_to_margin(*open_sp) {
-                            return delim == d && close_padding != open_padding;
-                        }
-                    }
-                    false
-                })
-            // these are in reverse order as they get inserted on close, but
-            {
-                // we want the last open/first close
-                err.span_label(*open_sp, "this delimiter might not be properly closed...");
-                err.span_label(*close_sp, "...as it matches this but it has different indentation");
-            }
+            self.report_error_prone_delim_block(*delim, &mut err);
         }
         err
     }
@@ -157,15 +142,11 @@ impl<'a> TokenTreesReader<'a> {
                 //only add braces
                 if let (Delimiter::Brace, Delimiter::Brace) = (open_brace, open_delim) {
                     self.matching_block_spans.push((open_brace_span, close_brace_span));
-                }
 
-                if self.open_braces.is_empty() {
-                    // Clear up these spans to avoid suggesting them as we've found
-                    // properly matched delimiters so far for an entire block.
-                    self.matching_delim_spans.clear();
-                } else {
+                    // Add all the matching spans, we will sort by span later
                     self.matching_delim_spans.push((open_brace, open_brace_span, close_brace_span));
                 }
+
                 // Move past the closing delimiter.
                 self.token = self.string_reader.next_token().0;
             }
@@ -183,15 +164,12 @@ impl<'a> TokenTreesReader<'a> {
                     if let Some(&(_, sp)) = self.open_braces.last() {
                         unclosed_delimiter = Some(sp);
                     };
-                    let sm = self.string_reader.sess.source_map();
-                    if let Some(current_padding) = sm.span_to_margin(self.token.span) {
-                        for (brace, brace_span) in &self.open_braces {
-                            if let Some(padding) = sm.span_to_margin(*brace_span) {
-                                // high likelihood of these two corresponding
-                                if current_padding == padding && brace == &close_delim {
-                                    candidate = Some(*brace_span);
-                                }
-                            }
+                    for (brace, brace_span) in &self.open_braces {
+                        if self.same_identation_level(self.token.span, *brace_span)
+                            && brace == &close_delim
+                        {
+                            // high likelihood of these two corresponding
+                            candidate = Some(*brace_span);
                         }
                     }
                     let (tok, _) = self.open_braces.pop().unwrap();
@@ -236,23 +214,68 @@ impl<'a> TokenTreesReader<'a> {
         let mut err =
             self.string_reader.sess.span_diagnostic.struct_span_err(self.token.span, &msg);
 
-        // Braces are added at the end, so the last element is the biggest block
-        if let Some(parent) = self.matching_block_spans.last() {
-            if let Some(span) = self.last_delim_empty_block_spans.remove(&delim) {
-                // Check if the (empty block) is in the last properly closed block
-                if (parent.0.to(parent.1)).contains(span) {
-                    err.span_label(span, "block is empty, you might have not meant to close it");
-                } else {
-                    err.span_label(parent.0, "this opening brace...");
-                    err.span_label(parent.1, "...matches this closing brace");
+        self.report_error_prone_delim_block(delim, &mut err);
+        err.span_label(self.token.span, "unexpected closing delimiter");
+        err
+    }
+
+    fn same_identation_level(&self, open_sp: Span, close_sp: Span) -> bool {
+        let sm = self.string_reader.sess.source_map();
+        if let (Some(open_padding), Some(close_padding)) =
+            (sm.span_to_margin(open_sp), sm.span_to_margin(close_sp))
+        {
+            open_padding == close_padding
+        } else {
+            false
+        }
+    }
+
+    fn report_error_prone_delim_block(&self, delim: Delimiter, err: &mut Diagnostic) {
+        let mut matched_spans = vec![];
+        let mut candidate_span = None;
+
+        for &(d, open_sp, close_sp) in &self.matching_delim_spans {
+            if d == delim {
+                let block_span = open_sp.with_hi(close_sp.lo());
+                let same_ident = self.same_identation_level(open_sp, close_sp);
+                matched_spans.push((block_span, same_ident));
+            }
+        }
+
+        // sort by `lo`, so the large block spans in the front
+        matched_spans.sort_by(|a, b| a.0.lo().cmp(&b.0.lo()));
+
+        // We use larger block whose identation is well to cover those innert blocks
+        // O(N^2) here, but we are on error reporting path, so it is fine
+        for i in 0..matched_spans.len() {
+            let (block_span, same_ident) = matched_spans[i];
+            if same_ident {
+                for j in i + 1..matched_spans.len() {
+                    let (inner_block, innert_same_ident) = matched_spans[j];
+                    if block_span.contains(inner_block) && !innert_same_ident {
+                        matched_spans[j] = (inner_block, true);
+                    }
                 }
-            } else {
-                err.span_label(parent.0, "this opening brace...");
-                err.span_label(parent.1, "...matches this closing brace");
             }
         }
 
-        err.span_label(self.token.span, "unexpected closing delimiter");
-        err
+        // Find the innermost span candidate for final report
+        for (block_span, same_ident) in matched_spans.into_iter().rev() {
+            if !same_ident {
+                candidate_span = Some(block_span);
+                break;
+            }
+        }
+
+        if let Some(block_span) = candidate_span {
+            err.span_label(
+                block_span.shrink_to_lo(),
+                "this delimiter might not be properly closed...",
+            );
+            err.span_label(
+                block_span.shrink_to_hi(),
+                "...as it matches this but it has different indentation",
+            );
+        }
     }
 }

src/test/ui/parser/deli-ident-issue-1.rs

@@ -0,0 +1,27 @@
+// ignore-tidy-trailing-newlines
+//
+// error-pattern: this file contains an unclosed delimiter
+#![feature(let_chains)]
+trait Demo {}
+
+impl dyn Demo {
+    pub fn report(&self) -> u32 {
+        let sum = |a: u32,
+                   b: u32,
+                   c: u32| {
+            a + b + c
+        };
+        sum(1, 2, 3)
+    }
+
+    fn check(&self, val: Option<u32>, num: Option<u32>) {
+        if let Some(b) = val
+        && let Some(c) = num {
+        && b == c {
+            //~^ ERROR expected struct
+            //~| ERROR mismatched types
+        }
+    }
+}
+
+fn main() { } //~ ERROR this file contains an unclosed delimiter

src/test/ui/parser/deli-ident-issue-1.stderr

@@ -0,0 +1,37 @@
+error: this file contains an unclosed delimiter
+  --> $DIR/deli-ident-issue-1.rs:27:65
+   |
+LL | impl dyn Demo {
+   |               - unclosed delimiter
+...
+LL |         && let Some(c) = num {
+   |                              - this delimiter might not be properly closed...
+...
+LL |     }
+   |     - ...as it matches this but it has different indentation
+...
+LL | fn main() { }
+   |                                                                 ^
+
+error[E0574]: expected struct, variant or union type, found local variable `c`
+  --> $DIR/deli-ident-issue-1.rs:20:17
+   |
+LL |         && b == c {
+   |                 ^ not a struct, variant or union type
+
+error[E0308]: mismatched types
+  --> $DIR/deli-ident-issue-1.rs:20:9
+   |
+LL |       fn check(&self, val: Option<u32>, num: Option<u32>) {
+   |                                                           - expected `()` because of default return type
+...
+LL | /         && b == c {
+LL | |
+LL | |
+LL | |         }
+   | |_________^ expected `()`, found `bool`
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0308, E0574.
+For more information about an error, try `rustc --explain E0308`.

src/test/ui/parser/deli-ident-issue-2.rs

@@ -0,0 +1,25 @@
+// ignore-tidy-trailing-newlines
+//
+// error-pattern: this file contains an unclosed delimiter
+#![feature(let_chains)]
+trait Demo {}
+
+impl dyn Demo {
+    pub fn report(&self,
+                a: u32,
+                b: u32,
+                c: u32) -> u32 {
+        return a + b + c;
+    }
+
+    fn check(&self, val: Option<u32>, num: Option<u32>) {
+        if let Some(b) = val
+        && let Some(c) = num {
+        && b == c {
+            //~^ ERROR expected struct
+            //~| ERROR mismatched types
+        }
+    }
+}
+
+fn main() { } //~ ERROR this file contains an unclosed delimiter

src/test/ui/parser/deli-ident-issue-2.stderr

@@ -0,0 +1,37 @@
+error: this file contains an unclosed delimiter
+  --> $DIR/deli-ident-issue-2.rs:25:65
+   |
+LL | impl dyn Demo {
+   |               - unclosed delimiter
+...
+LL |         && let Some(c) = num {
+   |                              - this delimiter might not be properly closed...
+...
+LL |     }
+   |     - ...as it matches this but it has different indentation
+...
+LL | fn main() { }
+   |                                                                 ^
+
+error[E0574]: expected struct, variant or union type, found local variable `c`
+  --> $DIR/deli-ident-issue-2.rs:18:17
+   |
+LL |         && b == c {
+   |                 ^ not a struct, variant or union type
+
+error[E0308]: mismatched types
+  --> $DIR/deli-ident-issue-2.rs:18:9
+   |
+LL |       fn check(&self, val: Option<u32>, num: Option<u32>) {
+   |                                                           - expected `()` because of default return type
+...
+LL | /         && b == c {
+LL | |
+LL | |
+LL | |         }
+   | |_________^ expected `()`, found `bool`
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0308, E0574.
+For more information about an error, try `rustc --explain E0308`.

src/test/ui/parser/issue-68987-unmatch-issue.rs

@@ -0,0 +1,12 @@
+// This file has unexpected closing delimiter,
+
+fn func(o: Option<u32>) {
+    match o {
+        Some(_x) =>
+            let _ = if true {};
+        }
+        None => {}
+    }
+} //~ ERROR unexpected closing delimiter
+
+fn main() {}

src/test/ui/parser/issue-68987-unmatch-issue.stderr

@@ -0,0 +1,14 @@
+error: unexpected closing delimiter: `}`
+  --> $DIR/issue-68987-unmatch-issue.rs:10:1
+   |
+LL |     match o {
+   |             - this delimiter might not be properly closed...
+...
+LL |         }
+   |         - ...as it matches this but it has different indentation
+...
+LL | }
+   | ^ unexpected closing delimiter
+
+error: aborting due to previous error
+

src/test/ui/parser/issues/issue-2354.rs

@@ -1,10 +1,8 @@
 fn foo() { //~ NOTE unclosed delimiter
-  match Some(10) {
-  //~^ NOTE this delimiter might not be properly closed...
+  match Some(10) { //~ NOTE this delimiter might not be properly closed
       Some(y) => { panic!(); }
       None => { panic!(); }
-}
-//~^ NOTE ...as it matches this but it has different indentation
+} //~ NOTE ...as it matches this but it has different indentation
 
 fn bar() {
     let mut i = 0;

src/test/ui/parser/issues/issue-2354.stderr

@@ -1,5 +1,5 @@
 error: this file contains an unclosed delimiter
-  --> $DIR/issue-2354.rs:15:52
+  --> $DIR/issue-2354.rs:13:52
    |
 LL | fn foo() {
    |          - unclosed delimiter

src/test/ui/parser/issues/issue-70583-block-is-empty-1.stderr

@@ -2,10 +2,10 @@ error: unexpected closing delimiter: `}`
   --> $DIR/issue-70583-block-is-empty-1.rs:20:1
    |
 LL | fn struct_generic(x: Vec<i32>) {
-   |                                - this opening brace...
+   |                                - this delimiter might not be properly closed...
 ...
 LL |     }
-   |     - ...matches this closing brace
+   |     - ...as it matches this but it has different indentation
 LL | }
    | ^ unexpected closing delimiter
 

src/test/ui/parser/issues/issue-70583-block-is-empty-2.stderr

@@ -1,8 +1,10 @@
 error: unexpected closing delimiter: `}`
   --> $DIR/issue-70583-block-is-empty-2.rs:14:1
    |
+LL |         match self {
+   |                    - this delimiter might not be properly closed...
 LL |             ErrorHandled::Reported => {}}
-   |                                       -- block is empty, you might have not meant to close it
+   |                                         - ...as it matches this but it has different indentation
 ...
 LL | }
    | ^ unexpected closing delimiter

src/test/ui/parser/macro-mismatched-delim-paren-brace.stderr

@@ -2,10 +2,10 @@ error: unexpected closing delimiter: `}`
   --> $DIR/macro-mismatched-delim-paren-brace.rs:5:1
    |
 LL | fn main() {
-   |           - this opening brace...
+   |           - this delimiter might not be properly closed...
 ...
 LL |     }
-   |     - ...matches this closing brace
+   |     - ...as it matches this but it has different indentation
 LL | }
    | ^ unexpected closing delimiter
 

src/test/ui/parser/mismatched-delim-brace-empty-block.stderr

@@ -1,12 +1,6 @@
 error: unexpected closing delimiter: `}`
   --> $DIR/mismatched-delim-brace-empty-block.rs:5:1
    |
-LL | fn main() {
-   |           - this opening brace...
-LL |
-LL | }
-   | - ...matches this closing brace
-LL |     let _ = ();
 LL | }
    | ^ unexpected closing delimiter