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[Tolk] Smart casts and control flow graph

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With the introduction of nullable types, we want the
compiler to be smart in cases like
> if (x == null) return;
> // x is int now
or
> if (x == null) x = 0;
> // x is int now

These are called smart casts: when the type of variable
at particular usage might differ from its declaration.

Implementing smart casts is very challenging. They are based
on building control-flow graph and handling every AST vertex
with care. Actually, I represent cfg not a as a "graph with
edges". Instead, it's a "structured DFS" for the AST:
1) at every point of inferring, we have "current flow facts"
2) when we see an `if (...)`, we create two derived contexts
3) after `if`, finalize them at the end and unify
4) if we detect unreachable code, we mark that context
In other words, we get the effect of a CFG but in a more direct
approach. That's enough for AST-level data-flow.

Smart casts work for local variables and tensor/tuple indices.
Compilation errors have been reworked and now are more friendly.
There are also compilation warnings for always true/false
conditions inside if, assert, etc.
This commit is contained in:
tolk-vm 2025-02-24 20:14:16 +03:00
parent f3e620f48c
commit 7bcb8b895f
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47 changed files with 3057 additions and 833 deletions
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13
tolk/src-file.cpp
View file

@ -18,6 +18,7 @@
#include "compiler-state.h"
#include <iostream>
#include <sstream>
#include <iomanip>
namespace tolk {
@ -146,9 +147,10 @@ void SrcLocation::show_context(std::ostream& os) const {
return;
}
SrcFile::SrcPosition pos = src_file->convert_offset(char_offset);
os << " " << pos.line_str << "\n";
os << std::right << std::setw(4) << pos.line_no << " | ";
os << pos.line_str << "\n";
os << " ";
os << " " << " | ";
for (int i = 1; i < pos.char_no; ++i) {
os << ' ';
}
@ -193,8 +195,11 @@ std::ostream& operator<<(std::ostream& os, const ParseError& error) {
}
void ParseError::show(std::ostream& os) const {
os << where << ": error: " << message << std::endl;
where.show_context(os);
os << loc << ": error: " << message << std::endl;
if (current_function) {
os << " // in function `" << current_function->as_human_readable() << "`" << std::endl;
}
loc.show_context(os);
}
} // namespace tolk