[flang-commits] [flang] 60b6730 - [flang] Better error recovery for missing THEN in IF construct

[Peter Klausler via flang-commits]

Author: Peter Klausler
Date: 2023-05-18T11:41:07-07:00
New Revision: 60b673023f54e899c727e32414fd89b646a147e4

URL: https://github.com/llvm/llvm-project/commit/60b673023f54e899c727e32414fd89b646a147e4
DIFF: https://github.com/llvm/llvm-project/commit/60b673023f54e899c727e32414fd89b646a147e4.diff

LOG: [flang] Better error recovery for missing THEN in IF construct

Presented with "IF (...)" with no following tokens in the statement,
diagnose a missing "THEN" instead of complaining about all of the
possible action statement initial tokens that could have been there
for a non-construct IF statement.

Fixes https://github.com/llvm/llvm-project/issues/62299.

Differential Revision: https://reviews.llvm.org/D150783

Added: 
    flang/test/Parser/missing-then.f90

Modified: 
    flang/lib/Parser/executable-parsers.cpp

Removed: 
    


################################################################################
diff  --git a/flang/lib/Parser/executable-parsers.cpp b/flang/lib/Parser/executable-parsers.cpp
index fc67d11a7ed75..92e7d25d93d3b 100644
--- a/flang/lib/Parser/executable-parsers.cpp
+++ b/flang/lib/Parser/executable-parsers.cpp
@@ -305,7 +305,8 @@ TYPE_CONTEXT_PARSER(
 TYPE_CONTEXT_PARSER("IF construct"_en_US,
     construct<IfConstruct>(
         statement(construct<IfThenStmt>(maybe(name / ":"),
-            "IF" >> parenthesized(scalarLogicalExpr) / "THEN")),
+            "IF" >> parenthesized(scalarLogicalExpr) /
+                    recovery("THEN"_tok, lookAhead(endOfStmt)))),
         block,
         many(construct<IfConstruct::ElseIfBlock>(
             unambiguousStatement(construct<ElseIfStmt>(

diff  --git a/flang/test/Parser/missing-then.f90 b/flang/test/Parser/missing-then.f90
new file mode 100644
index 0000000000000..ccaee3e801236
--- /dev/null
+++ b/flang/test/Parser/missing-then.f90
@@ -0,0 +1,8 @@
+! RUN: not %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck %s
+!CHECK: expected 'THEN'
+!CHECK-NOT: expected 'PAUSE'
+if (.TRUE.)
+!CHECK: expected 'THEN'
+else if (.FALSE.)
+end if
+end