[llvm-branch-commits] [clang] 5d21aed - Add release note for RecoveryExpr.

[Haojian Wu via llvm-branch-commits]

Author: Haojian Wu
Date: 2020-08-28T09:56:52+02:00
New Revision: 5d21aedfdbf0b85d65bad08b7b89913205de4b33

URL: https://github.com/llvm/llvm-project/commit/5d21aedfdbf0b85d65bad08b7b89913205de4b33
DIFF: https://github.com/llvm/llvm-project/commit/5d21aedfdbf0b85d65bad08b7b89913205de4b33.diff

LOG: Add release note for RecoveryExpr.

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst

Removed: 
    


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diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 7b1df2ed9c3f..83877d0d95a2 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -48,6 +48,46 @@ Major New Features
 
 - ...
 
+Recovery AST
+^^^^^^^^^^^^
+
+clang's AST now improves support for representing broken C++ code. This improves
+the quality of subsequent diagnostics after an error is encountered. It also
+exposes more information to tools like clang-tidy and clangd that consume
+clang’s AST, allowing them to be more accurate on broken code.
+
+A RecoveryExpr is introduced in clang's AST, marking an expression containing
+semantic errors. This preserves the source range and subexpressions of the
+broken expression in the AST (rather than discarding the whole expression).
+
+For the following invalid code:
+
+  .. code-block:: c++
+
+     int NoArg(); // Line 1
+     int x = NoArg(42); // oops!
+
+clang-10 produces the minimal placeholder:
+
+  .. code-block:: c++
+
+     // VarDecl <line:2:1, col:5> col:5 x 'int'
+
+clang-11 produces a richer AST:
+
+  .. code-block:: c++
+
+     // VarDecl <line:2:1, col:16> col:5 x 'int' cinit
+     // `-RecoveryExpr <col:9, col:16> '<dependent type>' contains-errors lvalue
+     //    `-UnresolvedLookupExpr <col:9> '<overloaded function>' lvalue (ADL) = 'NoArg'
+     //    `-IntegerLiteral <col:15> 'int' 42
+
+Note that error-dependent types and values may now occur outside a template
+context. Tools may need to adjust assumptions about dependent code.
+
+This feature is on by default for C++ code, and can be explicitly controlled
+with `-Xclang -f[no-]recovery-ast`.
+
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^