84 lines
2.6 KiB
TypeScript
84 lines
2.6 KiB
TypeScript
import { ParseError } from "../../worker-errors";
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import { ASTStep } from "../common/types";
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import * as D from "./grammar-types";
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/** Single item of the scope block stack */
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type BlockStackItem =
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| { type: "if"; line: number }
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| { type: "loop"; line: number }
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| { type: "function"; line: number };
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/** Stack to track the current scopes */
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type BlockStack = BlockStackItem[];
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/**
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* Check that the given line is valid to be the next line of
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* an inline if-statement. The next line of an inline if-statement
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* can only be an empty line or an else-clause.
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*
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* @param lineNum Line number of the line in code
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* @param line The line in parsed form
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*/
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const validateInlineIfNextLine = (lineNum: number, line: D.Line) => {
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if (line.type !== "blank" && line.type !== "else") {
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throw new ParseError(
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"Expected else clause or blank line after inline if-statement",
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{ line: lineNum }
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);
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}
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};
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/**
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* Build the executable AST from the parsed program, by filling in
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* the jump addresses of control flow statements and validating blocks.
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*
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* @param program Program in parsed form
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* @returns AST of the program
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*/
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export const buildAST = (program: D.Program): ASTStep[] => {
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const lines = program.list;
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const stack: BlockStack = [];
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const ast: ASTStep[] = [];
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for (let i = 0; i < lines.length; ++i) {
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const line = lines[i];
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// Function declaration or loop start: push block onto stack
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if (line.type === "function_decl" || line.type === "loop") {
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stack.push({ type: "function", line: i });
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}
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if (line.type === "if") {
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stack.push({ type: "if", line: i });
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// Check if the next line is valid to follow an inline if-statement
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if (line.statement && i + 1 < lines.length)
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validateInlineIfNextLine(i + 1, lines[i + 1]);
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}
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if (line.type === "else") {
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// Pop if-item from block stack
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const ifItem = stack.pop();
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if (!ifItem || ifItem.type !== "if")
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throw new ParseError("Unexpected else clause", { line: i });
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// Fill in the jump address for the corresponding if-statement
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const ifLine = ast[ifItem.line];
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if (!ifLine || ifLine.op.type !== "if") throw new Error("Bad stack item");
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ifLine.op.jump = i;
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}
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if (line.type === "blank") {
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// Pop block from stack
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const blockItem = stack.pop();
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if (blockItem) {
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// Fill in the jump address for the corresponding block
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const blockLine = ast[blockItem.line];
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if (!blockLine || blockLine.op.type !== blockItem.type)
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throw new Error("Bad stack item");
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// TODO: Check block type and act accordingly
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}
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}
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}
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return ast;
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};
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