Fix PR25627: constant expressions being odr-used in template arguments.

This patch ensures that clang processes the expression-nodes that are generated when disambiguating between types and expressi

Fix PR25627: constant expressions being odr-used in template arguments.

This patch ensures that clang processes the expression-nodes that are generated when disambiguating between types and expressions within template arguments as constant-expressions by installing the ConstantEvaluated ExpressionEvaluationContext just before attempting the disambiguation - and then making sure that Context carries through into ParseConstantExpression (by refactoring it out into a function that does not create its own EvaluationContext: ParseConstantExpressionInExprEvalContext)

Note, prior to this patch, trunk would correctly disambiguate and identify the expression as an expression - and while it would annotate the token with the expression - it would fail to complete the odr-use processing (specifically, failing to trigger Sema::UpdateMarkingForLValueToRValue as is done for all Constant Expressions, which would remove it from being considered odr-used). By installing the ConstantExpression Evaluation Context prior to disambiguation, and making sure it carries though, we ensure correct processing of the expression-node.

For e.g:
template<int> struct X { };
void f() {
const int N = 10;
X<N> x; // should be OK.
[] { return X<N>{}; }; // Should be OK - no capture - but clang errors!
}

See a related bug: https://bugs.llvm.org//show_bug.cgi?id=25627

In summary (and reiteration), the fix is as follows:

- Remove the EnteredConstantEvaluatedContext action from ParseTemplateArgumentList (relying on ParseTemplateArgument getting it right)
- Add the EnteredConstantEvaluatedContext action just prior to undergoing the disambiguating parse, and if the parse succeeds for an expression, carry the context though into a refactored version of ParseConstantExpression that does not create its own ExpressionEvaluationContext.

See https://reviews.llvm.org/D31588 for additional context regarding some of the more fragile and complicated approaches attempted, and Richard's feedback that eventually shaped the simpler and more robust rendition that is being committed.

Thanks Richard!

llvm-svn: 303492

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Prior to adding the new "expected-no-diagnostics" directive to VerifyDiagnosticConsumer, make the necessary adjustment to 580 test-cases which will henceforth require this new directive.

llvm-svn: 1

Prior to adding the new "expected-no-diagnostics" directive to VerifyDiagnosticConsumer, make the necessary adjustment to 580 test-cases which will henceforth require this new directive.

llvm-svn: 166280

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It's okay to refer to non-type template parameters anywhere they are
visible. Fixes the remaining two failures in Boost.ScopeExit.

llvm-svn: 102466

Fix an amusing typo that completely the re-introduction of parameters
for the purposes of parsing default arguments. In effect, we would
re-introduce the parameter with a default argument N times (wh

Fix an amusing typo that completely the re-introduction of parameters
for the purposes of parsing default arguments. In effect, we would
re-introduce the parameter with a default argument N times (where N is
the number of parameters preceding the parameter with a default
argument). This showed up when a defaulted parameter of a member
function of a local class shadowed a parameter of the enclosing
function. Fixes PR6383.

llvm-svn: 97534

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Keep an explicit stack of function and block scopes, each element of
which has the label map, switch statement stack, etc. Previously, we
had a single set of maps in Sema (for the function) along wit

Keep an explicit stack of function and block scopes, each element of
which has the label map, switch statement stack, etc. Previously, we
had a single set of maps in Sema (for the function) along with a stack
of block scopes. However, this lead to funky behavior with nested
functions, e.g., in the member functions of local classes.

The explicit-stack approach is far cleaner, and we retain a 1-element
cache so that we're not malloc/free'ing every time we enter a
function. Fixes PR6382.

Also, tweaked the unused-variable warning suppression logic to look at
errors within a given Scope rather than within a given function. The
prior code wasn't looking at the right number-of-errors count when
dealing with blocks, since the block's count would be deallocated
before we got to ActOnPopScope. This approach works with nested
blocks/functions, and gives tighter error recovery.

llvm-svn: 97518

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