Control flow analysis infrastructure

[rockorager]

Overview

Build a control flow graph (CFG) for Zig functions to enable path-sensitive lint rules.

What it unlocks

• Unreachable code detection
• Guaranteed null/error handling on all paths
• Use-after-free / use-after-move patterns
• Variable definitely-assigned checks
• Implement zlint rule 'returned-stack-reference' #13 (returned-stack-reference)
• Implement zlint rule 'useless-error-return' #17 (useless-error-return)

What's involved

• Build a CFG from the AST — basic blocks connected by edges for branches (if, switch, while, for), break, continue, return, try/catch
• Handle Zig-specific constructs — errdefer, defer, comptime branches, labeled blocks
• Path analysis — walk all paths for "does X happen on every/any path" questions

ZIR may help since it linearizes some of these constructs already.

Status

Not yet committed to. Tracking this so rules that need it have a place to point to.