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6f6c40a875
The solution is to favor the longest possible nest-name-specifier, and
drop other alternatives by using the guard, per per C++ [basic.lookup.qual.general].
Motivated cases:
```
Foo::Foo() {};
// the constructor can be parsed as:
// - Foo ::Foo(); // where the first Foo is return-type, and ::Foo is the function declarator
// + Foo::Foo(); // where Foo::Foo is the function declarator
```
```
void test() {
// a very slow parsing case when there are many qualifers!
X::Y::Z;
// The statement can be parsed as:
// - X ::Y::Z; // ::Y::Z is the declarator
// - X::Y ::Z; // ::Z is the declarator
// + X::Y::Z; // a declaration without declarator (X::Y::Z is decl-specifier-seq)
// + X::Y::Z; // a qualifed-id expression
}
```
Differential Revision: https://reviews.llvm.org/D130511
29 lines
1.3 KiB
C++
29 lines
1.3 KiB
C++
// RUN: clang-pseudo -grammar=cxx -source=%s --print-forest | FileCheck %s
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// Verify that we don't form a complete `::` nested-name-specifier if there is
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// an identifier preceding it.
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Foo::Foo() {} // No "Foo ::Foo()" false parse
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// CHECK: ├─declaration-seq~function-definition := function-declarator function-body
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// CHECK-NEXT: │ ├─function-declarator~noptr-declarator := noptr-declarator parameters-and-qualifiers
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int ::x;
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// CHECK: declaration~simple-declaration := decl-specifier-seq init-declarator-list ;
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// CHECK-NEXT: ├─decl-specifier-seq~INT
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void test() {
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X::Y::Z; // No false qualified-declarator parses "X ::Y::Z" and "X::Y ::Z".
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// CHECK: statement-seq~statement := <ambiguous>
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// CHECK: statement~expression-statement := expression ;
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// CHECK: statement~simple-declaration := decl-specifier-seq ;
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// CHECK-NOT: simple-declaration := decl-specifier-seq init-declarator-list ;
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// FIXME: eliminate the false `a<b> ::c` declaration parse.
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a<b>::c;
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// CHECK: statement := <ambiguous>
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// CHECK-NEXT: ├─statement~expression-statement := expression ;
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// CHECK-NEXT: │ ├─expression~relational-expression :=
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// CHECK: └─statement~simple-declaration := <ambiguous>
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// CHECK-NEXT: ├─simple-declaration := decl-specifier-seq ;
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// CHECK: └─simple-declaration := decl-specifier-seq init-declarator-list ;
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}
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