It is possible to create function-local named types:
func foo() any {
type named int
return named(0)
}
This patch makes sure they don't alias with named types declared at the
package scope.
Bug originally found by Damian Gryski while working on reflect support.
There used to be a difference between `byte` and `uint8` in interface
methods. These are aliases, so they should be treated the same.
This patch introduces a custom serialization format for types,
circumventing the `Type.String()` method that is slightly wrong for our
purposes.
This also fixes an issue with the `any` keyword in Go 1.18, which
suffers from the same problem (but this time actually leads to a crash).
This is used for example by the errors package, which contains:
if x, ok := err.(interface{ As(interface{}) bool }); ok && x.As(target) {
return true
}
The interface here is not a named type.
Non-constant type asserts are not yet implemented, but should be
relatively easy to add at a later time. They should result in a clear
error message for now.
There are a lot more fields that are important when comparing structs
with each other. Take them into account when building the unique ID per
struct type.
Example code that differs between the compilers:
https://play.golang.org/p/nDX4tSHOf_T
This commit fixes the following issue:
https://github.com/tinygo-org/tinygo/issues/309
Also, it prepares for some other reflect-related changes that should
make it easier to add support for named types (etc.) in the future.
This commit changes many things:
* Most interface-related operations are moved into an optimization
pass for more modularity. IR construction creates pseudo-calls which
are lowered in this pass.
* Type codes are assigned in this interface lowering pass, after DCE.
* Type codes are sorted by usage: types more often used in type
asserts are assigned lower numbers to ease jump table construction
during machine code generation.
* Interface assertions are optimized: they are replaced by constant
false, comparison against a constant, or a typeswitch with only
concrete types in the general case.
* Interface calls are replaced with unreachable, direct calls, or a
concrete type switch with direct calls depending on the number of
implementing types. This hopefully makes some interface patterns
zero-cost.
These changes lead to a ~0.5K reduction in code size on Cortex-M for
testdata/interface.go. It appears that a major cause for this is the
replacement of function pointers with direct calls, which are far more
susceptible to optimization. Also, not having a fixed global array of
function pointers greatly helps dead code elimination.
This change also makes future optimizations easier, like optimizations
on interface value comparisons.
A single *ssa.BasicBlock may be split in multiple LLVM basic blocks due
to typeassert instructions. This means the incoming block and outgoing
block are different. PHI nodes need to get the result from the outgoing
block, which was fixed before, but incoming branches need to branch to
the incoming block, not the outgoing block.
Branching to the outgoing block led to a LLVM verification error when
compiling the fmt package.
Originally found in (*fmt.pp).handleMethods.
When the underlying value of an interface does not fit in a pointer, a
pointer to the value was correctly inserted in the heap. However, the
receiving method still assumed it got the underlying value instead of a
pointer to it leading to a crash.
This commit inserts wrapper functions for method calls on interfaces.
The bug wasn't obvious as on a 64-bit system, the underlying value was
almost always put directly in the interface. However, it led to a crash
on the AVR platform where pointer are (usually) just 16 bits making it
far more likely that underlying values cannot be directly stored in an
interface.
