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[flang] Improve error recovery for bad/missing construct END statements

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When a multi-statement construct should end with a particular END statement
like "END SELECT", and that construct's END statement is missing or
unrecognizable, the error recovery productions should not misinterpret
a program unit END statement that follows and consume it as a misspelled
construct END statement. Doing so leads to cascading errors or a failed parse.

Differential Revision: https://reviews.llvm.org/D136896
This commit is contained in:
Peter Klausler
2022-10-10 13:47:12 -07:00
parent b203511c4f
commit 619b5bfc8d
6 changed files with 32 additions and 26 deletions
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4
flang/lib/Parser/Fortran-parsers.cpp
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@@ -384,7 +384,7 @@ TYPE_PARSER(construct<PrivateOrSequence>(Parser<PrivateStmt>{}) ||
// R730 end-type-stmt -> END TYPE [type-name]
TYPE_PARSER(construct<EndTypeStmt>(
recovery("END TYPE" >> maybe(name), endStmtErrorRecovery)))
recovery("END TYPE" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R731 sequence-stmt -> SEQUENCE
TYPE_PARSER(construct<SequenceStmt>("SEQUENCE"_tok))
@@ -607,7 +607,7 @@ TYPE_PARSER(
construct<Enumerator>(namedConstant, maybe("=" >> scalarIntConstantExpr)))
// R763 end-enum-stmt -> END ENUM
TYPE_PARSER(recovery("END ENUM"_tok, "END" >> SkipPast<'\n'>{}) >>
TYPE_PARSER(recovery("END ENUM"_tok, constructEndStmtErrorRecovery) >>
construct<EndEnumStmt>())
// R801 type-declaration-stmt ->

19
flang/lib/Parser/executable-parsers.cpp
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@@ -9,7 +9,6 @@
// Per-type parsers for executable statements
#include "basic-parsers.h"
#include "debug-parser.h"
#include "expr-parsers.h"
#include "misc-parsers.h"
#include "stmt-parser.h"
@@ -159,8 +158,8 @@ TYPE_PARSER(construct<Selector>(variable) / lookAhead(","_tok || ")"_tok) ||
construct<Selector>(expr))
// R1106 end-associate-stmt -> END ASSOCIATE [associate-construct-name]
TYPE_PARSER(construct<EndAssociateStmt>(
recovery("END ASSOCIATE" >> maybe(name), endStmtErrorRecovery)))
TYPE_PARSER(construct<EndAssociateStmt>(recovery(
"END ASSOCIATE" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1107 block-construct ->
// block-stmt [block-specification-part] block end-block-stmt
@@ -186,7 +185,7 @@ TYPE_PARSER(construct<BlockSpecificationPart>(specificationPart))
// R1110 end-block-stmt -> END BLOCK [block-construct-name]
TYPE_PARSER(construct<EndBlockStmt>(
recovery("END BLOCK" >> maybe(name), endStmtErrorRecovery)))
recovery("END BLOCK" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1111 change-team-construct -> change-team-stmt block end-change-team-stmt
TYPE_CONTEXT_PARSER("CHANGE TEAM construct"_en_US,
@@ -226,8 +225,8 @@ TYPE_CONTEXT_PARSER("CRITICAL construct"_en_US,
statement(Parser<EndCriticalStmt>{})))
// R1118 end-critical-stmt -> END CRITICAL [critical-construct-name]
TYPE_PARSER(construct<EndCriticalStmt>(
recovery("END CRITICAL" >> maybe(name), endStmtErrorRecovery)))
TYPE_PARSER(construct<EndCriticalStmt>(recovery(
"END CRITICAL" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1119 do-construct -> do-stmt block end-do
// R1120 do-stmt -> nonlabel-do-stmt | label-do-stmt
@@ -289,7 +288,7 @@ TYPE_CONTEXT_PARSER("nonlabel DO statement"_en_US,
// R1132 end-do-stmt -> END DO [do-construct-name]
TYPE_CONTEXT_PARSER("END DO statement"_en_US,
construct<EndDoStmt>(
recovery("END DO" >> maybe(name), endStmtErrorRecovery)))
recovery("END DO" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1133 cycle-stmt -> CYCLE [do-construct-name]
TYPE_CONTEXT_PARSER(
@@ -315,8 +314,8 @@ TYPE_CONTEXT_PARSER("IF construct"_en_US,
block)),
maybe(construct<IfConstruct::ElseBlock>(
statement(construct<ElseStmt>("ELSE" >> maybe(name))), block)),
statement(construct<EndIfStmt>(
recovery("END IF" >> maybe(name), endStmtErrorRecovery)))))
statement(construct<EndIfStmt>(recovery(
"END IF" >> maybe(name), namedConstructEndStmtErrorRecovery)))))
// R1139 if-stmt -> IF ( scalar-logical-expr ) action-stmt
TYPE_CONTEXT_PARSER("IF statement"_en_US,
@@ -345,7 +344,7 @@ TYPE_CONTEXT_PARSER("CASE statement"_en_US,
// R1151 end-select-rank-stmt -> END SELECT [select-construct-name]
// R1155 end-select-type-stmt -> END SELECT [select-construct-name]
TYPE_PARSER(construct<EndSelectStmt>(
recovery("END SELECT" >> maybe(name), endStmtErrorRecovery)))
recovery("END SELECT" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1145 case-selector -> ( case-value-range-list ) | DEFAULT
constexpr auto defaultKeyword{construct<Default>("DEFAULT"_tok)};

9
flang/lib/Parser/expr-parsers.cpp
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@@ -10,7 +10,6 @@
#include "expr-parsers.h"
#include "basic-parsers.h"
#include "debug-parser.h"
#include "misc-parsers.h"
#include "stmt-parser.h"
#include "token-parsers.h"
@@ -496,8 +495,8 @@ TYPE_CONTEXT_PARSER("ELSEWHERE statement"_en_US,
// R1049 end-where-stmt -> ENDWHERE [where-construct-name]
TYPE_CONTEXT_PARSER("END WHERE statement"_en_US,
construct<EndWhereStmt>(
recovery("END WHERE" >> maybe(name), endStmtErrorRecovery)))
construct<EndWhereStmt>(recovery(
"END WHERE" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1050 forall-construct ->
// forall-construct-stmt [forall-body-construct]... end-forall-stmt
@@ -527,8 +526,8 @@ TYPE_PARSER(construct<ForallAssignmentStmt>(assignmentStmt) ||
// R1054 end-forall-stmt -> END FORALL [forall-construct-name]
TYPE_CONTEXT_PARSER("END FORALL statement"_en_US,
construct<EndForallStmt>(
recovery("END FORALL" >> maybe(name), endStmtErrorRecovery)))
construct<EndForallStmt>(recovery(
"END FORALL" >> maybe(name), namedConstructEndStmtErrorRecovery)))
// R1055 forall-stmt -> FORALL concurrent-header forall-assignment-stmt
TYPE_CONTEXT_PARSER("FORALL statement"_en_US,

1
flang/lib/Parser/io-parsers.cpp
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@@ -9,7 +9,6 @@
// Per-type parsers for I/O statements and FORMAT
#include "basic-parsers.h"
#include "debug-parser.h"
#include "expr-parsers.h"
#include "misc-parsers.h"
#include "stmt-parser.h"

13
flang/lib/Parser/program-parsers.cpp
View File

@@ -9,7 +9,6 @@
// Per-type parsers for program units
#include "basic-parsers.h"
#include "debug-parser.h"
#include "expr-parsers.h"
#include "misc-parsers.h"
#include "stmt-parser.h"
@@ -31,10 +30,10 @@ namespace Fortran::parser {
// statement without an otherwise empty list of dummy arguments. That
// MODULE prefix is disallowed by a constraint (C1547) in this context,
// so the standard language is not ambiguous, but disabling its misrecognition
// here would require context-sensitive keyword recognition or (or via)
// variant parsers for several productions; giving the "module" production
// priority here is a cleaner solution, though regrettably subtle. Enforcing
// C1547 is done in semantics.
// here would require context-sensitive keyword recognition or variant parsers
// for several productions; giving the "module" production priority here is a
// cleaner solution, though regrettably subtle.
// Enforcing C1547 is done in semantics.
static constexpr auto programUnit{
construct<ProgramUnit>(indirect(Parser<Module>{})) ||
construct<ProgramUnit>(indirect(functionSubprogram)) ||
@@ -329,7 +328,9 @@ TYPE_PARSER(construct<InterfaceStmt>("INTERFACE" >> maybe(genericSpec)) ||
construct<InterfaceStmt>(construct<Abstract>("ABSTRACT INTERFACE"_sptok)))
// R1504 end-interface-stmt -> END INTERFACE [generic-spec]
TYPE_PARSER(construct<EndInterfaceStmt>("END INTERFACE" >> maybe(genericSpec)))
TYPE_PARSER(
construct<EndInterfaceStmt>(recovery("END INTERFACE" >> maybe(genericSpec),
constructEndStmtErrorRecovery >> pure<std::optional<GenericSpec>>())))
// R1505 interface-body ->
// function-stmt [specification-part] end-function-stmt |

12
flang/lib/Parser/stmt-parser.h
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@@ -90,8 +90,16 @@ constexpr auto atEndOfStmt{space >>
withMessage("expected end of statement"_err_en_US, lookAhead(";\n"_ch))};
constexpr auto bareEnd{noNameEnd / recovery(atEndOfStmt, SkipTo<'\n'>{})};
constexpr auto endStmtErrorRecovery{
("END"_tok >> SkipTo<'\n'>{} || ok) >> missingOptionalName};
// For unrecognizable construct END statements. Be sure to not consume
// a program unit's END statement.
constexpr auto progUnitEndStmt{
"END" >> (lookAhead("\n"_ch) || "SUBROUTINE"_tok || "FUNCTION"_tok ||
"PROCEDURE"_tok || "MODULE"_tok || "SUBMODULE"_tok ||
"PROGRAM"_tok || "BLOCK DATA"_tok)};
constexpr auto constructEndStmtErrorRecovery{
!progUnitEndStmt >> ("END"_tok >> SkipTo<'\n'>{} || ok)};
constexpr auto namedConstructEndStmtErrorRecovery{
constructEndStmtErrorRecovery >> missingOptionalName};
constexpr auto progUnitEndStmtErrorRecovery{
(many(!"END"_tok >> SkipPast<'\n'>{}) >>