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Simplify return-path checks #247

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Merged
zimri-leisher merged 1 commit into from
Sep 22, 2026
Merged

Simplify return-path checks #247

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31 changes: 12 additions & 19 deletions src/fpy/semantics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2898,21 +2898,15 @@ def visit_AstBlock(self, node: AstBlock, state: CompileState):
state.does_return[node] = any(state.does_return[n] for n in node.stmts)

def visit_AstIf(self, node: AstIf, state: CompileState):
# an if statement returns if all of its branches return
branch_returns = [state.does_return[node.body]]

for _elif in node.elifs:
branch_returns.append(state.does_return[_elif])

if node.els is not None:
branch_returns.append(state.does_return[node.els])
else:
# implicit else branch that falls through without returning
branch_returns.append(False)

state.does_return[node] = all(branch_returns)
# Without an else, the implicit branch can fall through.
state.does_return[node] = (
node.els is not None
and state.does_return[node.body]
and all(state.does_return[branch] for branch in node.elifs)
and state.does_return[node.els]
)

def visit_AstElif(self, node: Union[AstElif], state: CompileState):
def visit_AstElif(self, node: AstElif, state: CompileState):
state.does_return[node] = state.does_return[node.body]

def visit_AstDef(self, node: AstDef, state: CompileState):
Expand All @@ -2938,11 +2932,10 @@ def visit_AstExpr(self, node: AstExpr, state: CompileState):
state.does_return[node] = False
return
func = state.resolved_symbols[node.func]
if not is_instance_compat(func, BuiltinFuncSymbol) or not func.name == "exit":
state.does_return[node] = False
return
# builtin exit "returns" (really just ends call stack entirely)
state.does_return[node] = True
# builtin exit ends the call stack, so it also prevents fallthrough.
state.does_return[node] = (
is_instance_compat(func, BuiltinFuncSymbol) and func.name == "exit"
)

def visit_default(self, node, state):
assert not is_instance_compat(node, AstStmt)
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